Showing posts with label Charger. Show all posts
Showing posts with label Charger. Show all posts
Monday, March 18, 2013
Three Years On the Road
It was three years ago that the Z3 rolled out of the garage as a fully operational electric car. It seems like an appropriate time to run through some statistics, as well as some of the hi-lights and some of the low points that the car and I have experienced in the last 1096 days (there was a leap year in there).
Number of miles driven: 14032
Number of charge cycles: 742
Average depth of discharge: 34.6%
Greatest depth of discharge*: 93%
Total kWh's used: 4948
Total cost of charging the car at $0.075/kWh: $371.10
Total $ saved on not buying gas: $2001.62
Some of you may have noticed the new widget toward the bottom of the right hand column. You may have even noticed that my numbers don't seem to match it. I recently enrolled the car in the EVClub website, which is a nifty site whose intention is to track how many electric miles have been driven by it's members. They also provide this nifty widget you can place on your website to keep everyone up to date on your EV miles. Well when you enter the data for your car the first time, it asks for the number of electric miles you've driven so far and the price of gas. I entered the current price, but really what it needed was the average price. Thus the discrepancy. I assure you, the total above is correct, but the one in the widget is close enough for government work.
The saga begins...
Two months after it's launch I noticed a vibration in the drive line After disassembling the drive line I was able to isolate it to the motor and discovered that the balancing putty had fallen off the armature. After the manufacturers finish winding the armature, there is bound to be a slight imbalance in it. To correct this, and save the motor's bearings, they bake some putty on one side to even things up. Well mine fell off. Netgain had it shipped back and repaired all at their expense.
By the time the car was back on the road, it was mid summer, and I realized that I've grown soft in my middle aged years. A car with no AC was fine when I was 16 or 19. Not when I was 45. It sucked. But I wasn't the only one suffering. The Zilla controller was flashing warning lights at me, constantly warning me that it was in thermal cut back mode, dropping me down to 50% power. Clearly I was going to have to get some cooling for me and the controller. I couldn't address it then, and frankly stopped driving the car for the remainder of the summer. A trip here or there at night, but that was it.
That following September, I blew up my charger. A completely self inflicted wound, but this blog is all about honesty. While charging the car, I was measuring one of the batteries. The probe slipped and managed to touch part of the chassis and the battery terminal at the same time. The Manzanita charger is not an isolated charger, meaning that it is grounded to the chassis. Why, I have no idea. But the consequence of this is if you do what I did, your charger blows up. Fortunately, or unfortunately depending how you look at it, this is not an uncommon problem for people with Manzanita chargers, and Manzanita Micro has gotten rather good at fixing them with a quick turn-around time, and for a very reasonable cost.
The sharp minded among you will be saying to yourselves "Clearly he had something, probably a mounting bracket, too close to the terminal. What a poor design. What an idiot!!" And you'd be right. To address this, I could either spend a lot of time, effort and money to redesign the battery rack. That, of course, would be the right thing to do. OR, I could simply wrap all of those metal bits in rubber. Which is what I did. Only one degree up from "idiot" status, but it was a step in the right direction.
Nine months after the motor went back in, I notice the drive line wobbling again. You guessed it, the putty fell off. Again! Netgain to the rescue one more time.
This time, since the car was apart, I decided I was going to fix the cooling issues. I added a Masterflux AC system to the car, and a much larger radiator for the Zilla. But as the car went back on the road in early September after that work, I didn't get the opportunity to really put the new cooling systems to the test. That would have to wait for summer 2012.
Five months later (January 2012) I turn the charger on and hear a pop at the front of the car and the charger turns itself off. To make a long story short, the car had a frame leak, meaning that you could measure the high voltage system on the chassis. That is bad. I was shocked and sickened to discover that the motor was once again the problem. A build up of carbon dust from the degradation of the brushes resulted in a frame leak that I could not clear no matter how much air I pushed through the motor. Plus, I found one of the brushes had been drilled by Warfield (the people that build the motor) and it had started to crumble. Who knows where that crumbling carbon went and lodged itself! Netgain to the rescue once again. George decided he'd had enough of this motor and sent me a brand new one. I still can't sing his praises enough. But I'm certain he curses when ever he hears my name. George told me that he has my old motor in his garage and plans to put it in a Bricklin that he's been planning to build. I really hope it treats him better than it did me.
The summer of 2012 came and went and the cooling systems I'd installed the previous year worked great. I was cool, the Zilla was cool, we were both happy.
In July however, while checking to see if the batteries were still balanced at the bottom of the state of charge, I blew up my e-Xpert Pro meter. Another self inflicted wound. I didn't just blow it up, once I pulled it out of the dash, I realized it nearly caught fire. For the price of one brand new meter, the car was whole again.
September rolled along, I went to charge the car one morning and the charger emitted a series of loud pops, a couple bright flashes, and then some smoke. The charger made another trip back to the repair shop. Talking to Rich Rudman, the owner of Manzanita Micro, he said he believed it was due to a faulty set of mosfets they had received some time back. I got the charger back only to find that it wouldn't charge the car consistently. The current output would jump all over the place. So another trip back to Manzanita.
The last post I put up, from January, detailed a problem with more carbon build up in the motor. That was easily resolved by re-positioning the inlet for the motors cooling fan, and with the aid of a leaf blower hooked up the cooling duct. It blew every bit of carbon out of that motor.
There you have it. Three years worth of EV adventures summed up in a few paragraphs. I guess I focused primarily on the bad stuff. But the fact is that the good stuff wasn't one or two events. It was all the times between those problems. Really, it's any time I get to drive the car. I simply love it. The 14,000+ miles of driving bliss far and away, out weigh the troubles I've had.
I've kept close track of the costs associated with building the car, and I can tell you that it cost me as much, if not a bit more than a new Nissan Leaf would have cost me. Of course the Leaf wasn't available when I started building the car. Nissan hadn't even announced it. So would I swap the Z3 for a Leaf or another OEM electric car. I have to say, there is something very appealing to off-loading maintenance and repairs to a warranty claim. But missing the satisfaction of having built my own is too steep a price to pay. Truth be told, I want one of each. But that will have to wait.
Last week, I ordered some long over due parts for the car. I'm going to be upgrading the suspension. I will be able to bring the ride height back up to BMW's spec, and put on some slightly heavier springs to handle the extra 385 lbs the car gained. Should be fun.
*That excludes the two times I took the cells down to 0% state of charge. Once to bottom balance, and the second time to check if the cells were still balanced at the bottom after a year's use. They were.
Wednesday, January 30, 2013
13,000 EV Miles
No doubt the 2 or 3 people that read this blog have long lost interest since I haven't posted anything for 3 1/2 months. But as they say, no news is good news, and I would say that by and large, that applies here. I pulled into the garage yesterday after running a quick errand (a Frosty for a sick child), and I took note of the odometer reading. I delivered the Frosty and then entered the data in my spreadsheet and was surprised to see that the running total of EV miles I've driven added up to exactly 13,000. Now the 3 year anniversary of the car hitting the road is in a month and 1/2 or so, but this seemed noteworthy enough that I thought I'd post an update of how things are going and include some numbers for those who enjoy statistics.
Keen readers will remember the episode I went through, just about a year ago, with a high voltage leak to the chassis, which I traced back to a frame leak through the motor and ultimately resulted in getting a new motor from Netgain. George Hamstra was simply sick of repairing it and sending it back to me. On a side note, George told me he has that motor in his garage and intends to put it in his Bricklin conversion. I hope it does well for him. At any rate, in addition to putting the new motor in, George also sent me some new brushes to try out, ones he felt would produce less carbon dust and so were better suited for my application. He sent me (at his expense mind you) some Helwig Red Top brushes that are made of a harder compound than the standard brushes the Netgain motors come with.
You have to understand, Netgain Motors was born out of the EV drag racing community. The earlier drag racers kept burning up their GE motors. George and others saw different opportunities to improve the motors here and there. They were working with Warfield Electric on building motors that incorporated their changes. Before long they had a completely new beast on their hands and decided to start selling them. The brushes they chose were of a softer carbon compound, ideal for pushing high current to the armature Under drag racing conditions, the motor would generally fail for some other reason long before the brushes did. But under low current applications, like driving to the store for milk and such, the brushes tended to wear out much faster and give off a lot of carbon dust. The Helwig brushes have worked out so well for them that they've made them available on new motors.
Understanding that, we get back to my car and the unexpected change I noticed after I installed the new motor with the new Helwig brushes. Suddenly, the car was more efficient. About 14% more efficient to be precise. Jack Rickard of EVTV ran experiments with an old WarP 9 motor he had at his shop, and found the same improvement. Well, a great deal of time has passed, and I've put many more miles on the car, 4797 to be precise. I thought I'd take a look at the numbers to see if the increase in efficiency has held true. The thing is, I realized that I'd been doing the math wrong. Well, the truth is, I knew I was doing it wrong, but I was too lazy to fix it, thinking the difference would be minimal. To sum up, I was taking all the trips I made, and averaging the Watt hours per mile used. The trouble is, the 275 Watt hours per mile used on a 35 mile trip was being averaged equally with the 378 Watt hours per mile on a 4 mile trip. Anyone can see, those numbers needed to be weighted differently since the distance was different. The solution is easy: add up all the miles driven and divide it by the sum of kilowatt/hours used.
What did we get? As I mentioned, I've driven 4797 miles since the brush replacement, and I've used a total of 1526.46 Kilowatt/hours. That works out to 318 Watt hours per mile. In comparison, I grabbed a 4804 mile sample of data from before the brush swap and noted that I'd used 1779.72 Kilowatt/hours, which works out to 370 Watt hours per mile. So does the 14% efficiency gain still hold water? 370 - 14%(51.8) = 318.2. Apparently so. I knew the way I was calculating the data before wasn't going to be wildly inaccurate, or even mildly for that matter. But it's encouraging to see that numbers still hold to be true.
Moving on. A couple weeks ago I plugged the car in, turned on the charger and heard a familiar "pop" come from the front of the car. I recognized it immediately as the same "pop" I'd heard before when the motor had become caked with carbon dust and there was a mini flash over in the motor. What the...?!!! The only way this would happen was if the carbon dust given off by the brushes wasn't being blown out. Since the Manzanita charger is grounded to the chassis, when you turn on the charger, if it senses a path from the chassis to the battery pack, it will either throw the circuit breaker in the charger itself, or blow up. I've had it do both. For the gory details of each, feel free to look further back in the blog. Suffice it to say, you don't want to accidentally touch a battery terminal and the chassis with a multi-meter probe at the same time when you're charging. Anyway, clearly I had a build up of carbon again! How could this happen? I've got a fan forcing air into the motor for chrissake! It should be blowing all that dust out.
I checked the fan, and it was running, but the output was very low. I looked at the filter and found that it was caked with dirt. Ahhhh. I'd cleaned it about 6 months earlier, but clearly there's a problem. Well the problem is really quite simple. Having no way to locate the fan and the filter higher up in the motor compartment, I mounted it on a tray right next to the motor. Meaning that the fan and the filter are about 9" off the ground, right were the dirtiest air is. You may have noticed that every manufacturer locates the air intake for their cars as high up in the engine compartment as possible. I'm thinking that may be intentional. I took the filter off and the flow of air was much better, like I expected it to be.
So now I'm left with two problems. First, the motor is full of dust and I need to blow it out. Second, I need to figure out what to do about this filter location; clearly where it's at is not the best place for it. Last time I had a dust problem with the motor, I used compressed air to blow it out. That worked pretty well as a huge plume of dust came out when I aimed the air gun into it. The problem is, I have to take the motor's shroud off, and to do that I have to take out the batteries over the motor and to do that I have to ... you get the picture. Curse the idiot that designed this!!! But then I had a flash of inspiration. What If I simply hook up my leaf blower to the inlet hose, the one that runs from the fan to the motor. Leaf blowers put out a crazy amount of air. Oh, now this will be good. Or at least fun.
It wasn't easy, but I was able to get to the inlet hose and basically taped the end of my leaf blower to it using my favorite tape in the world, gaffer's tape. It's basically black duct tape, but easier to tear. I had my daughter sit in the car and rev the motor up to about 3500 RPM, and I turned the blower on. I was very pleased to see a plume of black dust come out the back of the motor (and also a bit disturbed). I let it run this way for three or four minutes until I was confident it had expelled all the free carbon it could. The great thing was, I could put my hand at the back of the motor and feel a tremendous volume of air coming out. I started to wonder, could I some how use this leaf blower as my motor fan? Apart from it being impractical, it would make the Z3 the noisiest EV on the road, ever. No, what I really need to do is sort out the filter location problem.
With the fan located low like it was, it's collecting dust at a much faster rate, and ultimately choking the motor. I looked, thought, measured, looked, thought some more and came up with nothing. There is simply nowhere else to locate that filter. Then I had a thought. what if I eliminated the filter completely? Stick with me for a moment. The Netgain motors come with a screen covering the front bell housing, and the brushes. People run them like this all the time. The problem is some dirt and sand will inevitably get in and get on the armature and brushes cause them to wear prematurely. OK, so that's the trade off. But now, what if the inlet for that air came from a place that was less prone to see dirt and sand in the first place? After all, the front of the motor sits right where you would expect most of the dust and grime to be, so if I could find a place for the inlet that would provide cleaner air than that, I should be good. What I found was that there was a way to run a 3" hose from the fan inlet up in front of the firewall and just behind the large battery pack that's over the motor. It's shielded from the main airflow when the car is moving down the road, yet it's got an open area large enough that it can easily get all the air it needs. I checked and the output of the fan was terrific. As far as I'm concerned, problem solved. It's true that a bit of dirt may be blown into the motor, but I think this is a far better solution than cleaning the filter weekly to ensure good airflow through the motor.
The truth is, I'd love to get a fan that would push more air into the motor. The one I have pushes 120 CFM. George even said that's likely too low. The problem again is one of space. The fans I've found that push more air won't fit in the space I have. I keep an open eye out for one, from time to time I comb through the interwebs looking for a suitable candidate. So far, no luck.
That's all for now, but check back in early March on the car's 3rd anniversary as I'll post some more stats.
Monday, October 15, 2012
EVCCON 2012, Charging, and a Watchdog
EVCCON 2012
You may remember that my father and I took the Z3 out to Missouri last year for the inaugural EVCCON. It was a fantastic event and before it even ended, I decided that Dad and I would return to EVCCON 2012. There was a big difference this year in that we didn't take the car along with us. Having the car out there last year was terrific, but trailer-ing it out there was stressful, expensive, and it took three days each way. So this year the car waited back in the garage while we went to Missouri.
There has been plenty written of the convention on some very well written blogs, particularly on Mike Brown's blog about his Porsche 914 conversion, ( day 1, day 2 and day 3), and of course on EVTV. What I was most taken back by was the quality of the builds this year. I've been told by a number of people that they think I did a great job on the Z3. Compared to most conversions I've seen, it is great. Virtually all of the people that brought cars to this year's convention attended last year's and had a chance to see all of the cars that were brought at that time. There were a handful of car's at last years convention that made the Z3 look like a kindergarten project. It was evident by everyone that saw them, that they were clearly a different animal. In fact, it's clear that the community has decided those cars are the new standard. If you were going to convert a car, they were the benchmark that you need to aim for. A challenge that all took seriously.
The quality of the cars this year was simply outstanding. Everyone had all the components laid out and organized better than you'd expect an OEM to do. All of the wiring was routed perfectly and protected in looms. The connectors all neat and orderly, everything labeled. Looking in to these cars was like looking in jewelry boxes. Just astounding. Here's a sampling of a few. I wish I'd grabbed more photos.
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| Fred Behning and his MGTD |
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| Jeff Greeson's 914. Take away that blue cord and it's looks like a show piece. |
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| John Allen's Celica. A beautiful job in every respect. |
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| Kevin Heath and his RX8. He has every reason to be proud of this build. |
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| Jason Horack's Daytona. Well laid out, neat and tidy. |
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| Dale Friedhoff's Ranger. It won best wiring/layout award. |
If I'm not mistaken, last year Dad and I were the only father/son team at the convention. Well apparently that inspired a few others. Several decided they wanted to share the experience with their fathers as well. I was thrilled to see that list grow to 5 teams. We took a moment to pose in front of Jack Rickard's original Speedster, along with Jack.
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| Left to Right, Me, my dad Bill, John Allen and his father, Nabil Hanke , John Hanke, Jack Rickard, Fred Behning and his dad Fred, Brandon Hollinger and his father on the end. |
After a public car show in the park, the EVs went on parade through town and back to a local hotel were many of the attendees were staying. They rounded up all the EVs that were in the parade for a photo op.
I think there are 33 cars in the photo, and I know of 5 others that didn't make it. So that brings the total to 38 EVs at the convention by my count. Not a bad turnout. If you have the means to attend, I encourage you not to miss EVCCON 2013. They are only going to get better from here on out.
Charger News
You may remember from my last post that my charger up and exploded on me. It went back to Manzanita and they repaired it in a couple days and had it back to me right quick. I think the charger was out of the car for less than a week. All seemed well until a week after the install I noticed the charger behaving very erratically. Though I'd dialed in 20 amps of current, I saw the meter bounce all around from 18 to 2 then 10 then 3 then 5 amps. It was clear that it wasn't healthy.
I contacted Manzanita again and explained what it was doing. They asked me to take notes for a while to see if we could see a pattern to help them determine a cause. If there was a pattern somewhere buried in the data I gave them, it escaped me. After a couple weeks, we decided they needed it back to fix it. I took it out and mailed it the day before Dad and I left for EVCCON.
As it happens, Rich Rudman owner Manzanita Micro was one of the featured speakers at EVCCON, so I got to talk to him about the charger. I offered to let him pick my brain about it's behavior hoping that he might have some insight into why it was doing what it was doing. Instead it turned into a very short conversation. Rich asked me if it was behaving erratically, and listed off a few of the key characteristics of the behavior. I said "Yes! Exactly!" He said "Yeah... we don't know what's causing that." Apparently they've seen this a few times. They suspect a specific chip on the power board is causing it. When they come across this, they replace a few key components and that resolves the problem.
I got it back last Wednesday, they had it for about 2 weeks, and so far, I'd say they nailed it. It has been rock solid reliable. Boy, do I like that. They really are a first rate shop.
A Watchdog Circuit
It's happened twice now, which isn't a lot, but enough to make me a bit nervous. The charger which usually cuts off when the pack reaches 164.5 volts has error-ed during the constant voltage portion of the charge cycle. Instead of cutting off the charge in 10 minutes I set it for, it was well past 15 minutes, and I turned it off manually because the battery was going too high. I was present on both occasions to catch it and prevent it from over charging the batteries. But that begs the question, how many times did I not catch it because I wasn't there to watch?
The truth is, the charger is pretty reliable, but it uses electronic components to process that logic and is subject to the same faults any electronic component is. How many times does you computer do something unexpected? The world is an imperfect place. To that end, I've always thought that it would be worth while to have a separate circuit watching the charge cycle, one that had the ability to cut off the charge if things got out of hand. Fortunately a couple simple components allow anyone with a Manzanita Micro charger to do just that. I believe that other chargers have this capability as well, but I don't own any of them, so I can't say.
The Manzanita chargers were built incorporating what Manzanita calls the REG Bus. I hear it does many things when coupled with other hardware that they sell. But the truth is, I only need to use one of those functions, and that's the one that allows me to stop the charger.
Pin 1 on the REG Bus supplies 5 volts DC. Pin 2 has no voltage on it; however, if pin 2 sees 5 volts, the charger interprets this as an over charge condition and shuts the charging cycle off. The charger remains on, with the fans cooling it, but the charging cycle terminates. The bad side is, if you remove that 5 volts from pin 2, the charger immediately starts charging again. So the trick is to get pin 1 and 2 shorted under the right conditions and leave them connected until the over charge condition goes away. Enter the JLD 5740 volt meter. At $37.50, it's a bargain.
The 5740 will measure anything from 0 - 500 Volts, DC or AC should you need it. It has 2 relays that you can set independently. You can set a relay to latch closed at one voltage, and open at a different voltage. In this way, you can build in any logic for on/off you want. Here's how I set mine up.
When I turn the meter on, the relay is open. As the charge cycle runs, the voltage rises to the expected 164.5 volts. If for some reason, the charger misses it's target, the meter is set to close the relay at 165.2 volts. When the relay closes, the wire from pin 1 is shorted to the wire from pin 2 and the charger stops dead. That voltage is low enough that no cell in the system will exceed 3.6 volts. That relay then is latched closed until the voltage should drop below 158 volts. Since the resting voltage of the system, after a charge is 160, then the meter will never (without intervention) open that relay, and the charger will never restart.
When I built the car, I positioned a small switch under the charging door. When that door is open the switch sends 12 volts to the charger, and it's presumed that I'm charging and the car is plugged in. I run that 12 volt signal to the Zilla, which sees it and disables the car from moving. I've simply spliced into that line and use that signal to power a separate relay, that then powers the meter. I've incorporated the whole thing in a project box.
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| Notice the neat glowing switch on top of the box. |
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| The switch is depressed and the meter is on. |
I've run the power from the switch in the charging port to a second switch in the project box. If I want to use the meter to watch the charger, I simply press that button and the meter comes on. When I press the switch again, or if I close the charging port door, the meter is turned off. I don't need for it to be on when I'm not charging, so there's no reason to have that parasitic load running.
The only thing I haven't mentioned is that the 12V from the car that powers the meter first runs through a small 3 Watt DC to DC converter that isolates the high voltage on the meter from the car's 12V system. We don't want the high voltage system leaking back to the chassis. Pretty slick, and the whole thing cost less than $50 and it works great.
Saturday, September 1, 2012
Heat: Not So Good for Chargers Either
A couple weeks ago, on a Monday morning, we were in off peak hours and I
figured it would be a good time to top off the batteries before I ran
the day's errands. You may remember that I recently destroyed my eXpert
Pro meter by re-applying the pack voltage to it and not removing 12V
power first. By the way, DON'T DO THAT! Any way, I'd received a
new one, but I hadn't yet installed it. Without it, I have no idea how much
current I'm pushing to the batteries, so I need to keep an eye on them to
be sure I'm not over charging them. The fact is you learn things when
you watch what the batteries during charging. Over time, I've learned quite a bit, and by
watching them closely I can pretty much tell what's going on and predict when
the charger will terminate.
At any rate, I know which cell will start to rise above 3.45V first, so I put a meter on it and started the charger. For me, 3.45V is the top of the charge. There simply isn't enough energy put into the cells above that point to justify the potential risk and damage to the cells by getting them to the manufacturer's 3.6V. Ten minutes later, I walked out to see the voltage on the cell had climbed from it's initial reading of 3.26V up to 3.380V. I know by experience that means I'm about 35 minutes away from 3.45V when the charger should terminate it's charging sequence. So you can imagine my surprise when I walked out 25 minutes later and found the battery at 3.364V, and the charger still running. The voltage had dropped, yet the charger was still running. I stood there for a moment, completely confused, it just didn't compute in my head. Kind of like walking into your favorite BBQ place and seeing that it's full of vegans. Not that there's anything wrong with it, but it just doesn't make sense.
Figuring that the charger must have just gotten confused (after all it does have a simple logic board in it), I figured I'd just reboot it. I turned it off, waited 4 or 5 seconds and turned it back on. The moment I turned it on, there was a succession of 3 pops, with the last one being quite loud and producing a bright orange flash and rush of hot gas shooting out the charger's vent port. This was followed by me yelling "Oh shoot!", or something similar but perhaps more colorful. I turned the charger back on... nothing. Wasn't too surprised by that. I checked the breaker on the house and had not tripped, so whatever failed in the charger failed in such a way that it simply consumed all the power coming into it and blew up, rather than shorting. Or at least that's my take on it.
In either case, there was no doubt that I was going to need to remove the charger and send it back to Manzanita Micro for repair. This was the second time I've had to do this. The first was entirely self inflicted when I mistakenly shorted one of the batteries to the chassis with my multi-meter probe, while the car was charging. That blew up the AC rectifier and melted the end of my probe. I had no idea what happened here, but I boxed it up, got an RMA number and away it went to Washington.
It arrived in their shop on Friday and they sent me a note Monday afternoon that it was repaired, tested and ready for shipment. Remarkably fast turn-around. I called and spoke with Clarice, their office manager, to ask if they knew what caused the failure. Clarice has seen enough repairs that she can recognize the likely cause of the failure just by looking at the parts that were replaced. In this circumstance, both IGBTs failed as well as a capacitor. She said she'd honestly never seen anything like it, but she'd ask Rich when he got it. Rich thinks that one of the IGBTs failed and when it did, it took the other with it. He thinks heat may have been a contributing factor. This is where things get interesting and where there may be a lesson that all of you can learn at my expense.
As regular readers of this blog are aware, I live in Phoenix Arizona, which is slightly north of, and roughly rock throwing distance from Hell. It's not uncommon for the inside of my garage to be 105°F. If my wife pulls her car in after getting home from work, as it ticks itself cool, all the heat that was happily stored in all of that steel, gradually works it's way into the garage raising the temperature well over 110°F. It's lovely.
Here's the thing. Two years ago the car lived through it's first summer as an EV. A significant portion of that summer saw the car dis-assembled because I had sent the motor back to Netgain because the balancing putty had fallen off. Plus I took the opportunity to redo the battery layout. So when it was back on the road in late July and I was charging it on a regular basis, I would come out to find the charger's yellow light flashing at me. I went back to read the manual to find out what that meant, and I couldn't find a reference to what that was all about anywhere. I figured it was just an oddity with this charger. What it really was, was the charger warning me it was over heating. I blissfully ignored this warning for the remaining portion of the summer.
As it happens, the car was taken apart for a good portion of the following summer to again fix a balancing putty issue on the motor, and to add air conditioning to the car. In fact, I didn't get it back on the road until the first week of September, just in time to tow it out to EVCCON 2011. But even then I would see the flashing yellow when charging, but by then I'd figured out what it was so I would dial the current back until the light stopped flashing.
That's been my modus operandi this summer. I'd turn the charger on and dial in between 21 and 22 amps. I'd poke my head back into the garage in 20 minutes or so and if the charger was over heating, I'd turn it down. About 90% of the time, it was over heating. I'd turn it down to 16 amps or so. In retrospect, I think this behavior, and the initial instances of ignoring the warning, damaged the charger over time. Heat is the enemy of all circuitry and when the charger was overheating, it felt quite literally like a blow drier firing out of that little vent port. So my advice to you is don't to this. I realize that most of you don't live in such hot climates, but for the few that do, pay attention to your charger. Heat kills.
At this point, I intend to charge at 16 amps or so during the hotter months to protect the charger. It's remarkable how much cooler the unit runs at that current level. The problem is the charger was configured at a higher current level. That means if I charge at a lower current level, there's a risk that the charger will overshoot the voltage I've set and consequently over charge the batteries. Re-tuning the charger for a lower level is possible, but such a huge pain in the butt that I don't want to do it for the 1 month it's necessary before cooler weather arrives. But I would like to be able to charge at any level I like and not risk over charging the cells. I do have a solution in the works which I will be implementing and writing about soon, so stay tuned for that. In the mean time, I'm going to have to watch the end of the charging curve very carefully to protect the batteries.
At any rate, I know which cell will start to rise above 3.45V first, so I put a meter on it and started the charger. For me, 3.45V is the top of the charge. There simply isn't enough energy put into the cells above that point to justify the potential risk and damage to the cells by getting them to the manufacturer's 3.6V. Ten minutes later, I walked out to see the voltage on the cell had climbed from it's initial reading of 3.26V up to 3.380V. I know by experience that means I'm about 35 minutes away from 3.45V when the charger should terminate it's charging sequence. So you can imagine my surprise when I walked out 25 minutes later and found the battery at 3.364V, and the charger still running. The voltage had dropped, yet the charger was still running. I stood there for a moment, completely confused, it just didn't compute in my head. Kind of like walking into your favorite BBQ place and seeing that it's full of vegans. Not that there's anything wrong with it, but it just doesn't make sense.
Figuring that the charger must have just gotten confused (after all it does have a simple logic board in it), I figured I'd just reboot it. I turned it off, waited 4 or 5 seconds and turned it back on. The moment I turned it on, there was a succession of 3 pops, with the last one being quite loud and producing a bright orange flash and rush of hot gas shooting out the charger's vent port. This was followed by me yelling "Oh shoot!", or something similar but perhaps more colorful. I turned the charger back on... nothing. Wasn't too surprised by that. I checked the breaker on the house and had not tripped, so whatever failed in the charger failed in such a way that it simply consumed all the power coming into it and blew up, rather than shorting. Or at least that's my take on it.
In either case, there was no doubt that I was going to need to remove the charger and send it back to Manzanita Micro for repair. This was the second time I've had to do this. The first was entirely self inflicted when I mistakenly shorted one of the batteries to the chassis with my multi-meter probe, while the car was charging. That blew up the AC rectifier and melted the end of my probe. I had no idea what happened here, but I boxed it up, got an RMA number and away it went to Washington.
It arrived in their shop on Friday and they sent me a note Monday afternoon that it was repaired, tested and ready for shipment. Remarkably fast turn-around. I called and spoke with Clarice, their office manager, to ask if they knew what caused the failure. Clarice has seen enough repairs that she can recognize the likely cause of the failure just by looking at the parts that were replaced. In this circumstance, both IGBTs failed as well as a capacitor. She said she'd honestly never seen anything like it, but she'd ask Rich when he got it. Rich thinks that one of the IGBTs failed and when it did, it took the other with it. He thinks heat may have been a contributing factor. This is where things get interesting and where there may be a lesson that all of you can learn at my expense.
As regular readers of this blog are aware, I live in Phoenix Arizona, which is slightly north of, and roughly rock throwing distance from Hell. It's not uncommon for the inside of my garage to be 105°F. If my wife pulls her car in after getting home from work, as it ticks itself cool, all the heat that was happily stored in all of that steel, gradually works it's way into the garage raising the temperature well over 110°F. It's lovely.
Here's the thing. Two years ago the car lived through it's first summer as an EV. A significant portion of that summer saw the car dis-assembled because I had sent the motor back to Netgain because the balancing putty had fallen off. Plus I took the opportunity to redo the battery layout. So when it was back on the road in late July and I was charging it on a regular basis, I would come out to find the charger's yellow light flashing at me. I went back to read the manual to find out what that meant, and I couldn't find a reference to what that was all about anywhere. I figured it was just an oddity with this charger. What it really was, was the charger warning me it was over heating. I blissfully ignored this warning for the remaining portion of the summer.
As it happens, the car was taken apart for a good portion of the following summer to again fix a balancing putty issue on the motor, and to add air conditioning to the car. In fact, I didn't get it back on the road until the first week of September, just in time to tow it out to EVCCON 2011. But even then I would see the flashing yellow when charging, but by then I'd figured out what it was so I would dial the current back until the light stopped flashing.
That's been my modus operandi this summer. I'd turn the charger on and dial in between 21 and 22 amps. I'd poke my head back into the garage in 20 minutes or so and if the charger was over heating, I'd turn it down. About 90% of the time, it was over heating. I'd turn it down to 16 amps or so. In retrospect, I think this behavior, and the initial instances of ignoring the warning, damaged the charger over time. Heat is the enemy of all circuitry and when the charger was overheating, it felt quite literally like a blow drier firing out of that little vent port. So my advice to you is don't to this. I realize that most of you don't live in such hot climates, but for the few that do, pay attention to your charger. Heat kills.
At this point, I intend to charge at 16 amps or so during the hotter months to protect the charger. It's remarkable how much cooler the unit runs at that current level. The problem is the charger was configured at a higher current level. That means if I charge at a lower current level, there's a risk that the charger will overshoot the voltage I've set and consequently over charge the batteries. Re-tuning the charger for a lower level is possible, but such a huge pain in the butt that I don't want to do it for the 1 month it's necessary before cooler weather arrives. But I would like to be able to charge at any level I like and not risk over charging the cells. I do have a solution in the works which I will be implementing and writing about soon, so stay tuned for that. In the mean time, I'm going to have to watch the end of the charging curve very carefully to protect the batteries.
Monday, April 23, 2012
What An Ordeal
The few of you who read this blog have probably wondered what's been going on with the Z3. When I last left you, I'd received the new motor, had put the new split top, harder brushes in and was seating them by running the motor off of a 12V battery. Well, quite a lot has happened, and frankly, it wasn't all good. So sit back and enjoy the saga.
Once I installed the new brushes and turned the motor on, it made a hell of a racket for the first few hours. I remember seeing a video John Allen had made when he was breaking in new brushes for his Warp 9, and I was struck by how loud it was, so I wasn't too surprised when mine made similar noises. I ran the motor for 100 hours and at the end, it sounded as smooth as silk. Job done!
I mounted the motor up to the transmission and tightened up all the bolts and called it a day, planning to reinstall the motor/transmission back into the car the next day. During the night, I realized I'd done something kind of stupid. The manual for the car states that you should put a little grease on the input shaft before you mate it up to the motor. It already had a film of grease on it, but I thought more is better. When thinking about it that evening, I realized that I had cleaned off a little grease I'd found on the flywheel. It was in a pattern that looked like it had been thrown off the shaft. It was at that point I realized more is not better, and I'd set myself up for a greasy, slip prone clutch. So I took the tranny off the motor, cleaned the shaft of excess grease and mounted it back up. It only took 45 minutes or so, so it wasn't that bad. I'm telling this story so that if anyone out there reading this can learn a lesson from my stupidity, then I've served some purpose on this planet.
Moving on. The motor/transmission assembly went in to the car later that day without a hitch, and thanks to my dad who came out to help me. I mounted up the drive line and started the process of re-assembling the car. It went quite smooth really. I was making one of the last battery connections when I leaned my elbow on the chassis, and it felt like I got stabbed or cut. I remember thinking that I didn't remember the bolt I leaned on being particularly sharp. I touched it again and realized that I didn't get stabbed, I got shocked. That's right my friends, the leak, which I was trying to get rid of, the one for which I'd been sent a replacement motor, was not gone.
Talk about a kick in the teeth. I started testing and dis-assembling everything and came to the conclusion that, once again, the source of the leak was in the motor. How could this be?!!! I was absolutely gutted and just walked away from the car for what ended up being the whole weekend while I thought about what to do.
I decided what I had to do was figure out, definitively if it was the motor or something else. I decided the best way to do that was to assemble all of the components completely, but leave the motor out of the assembly process. In place of the motor, I simply ran a cable from the Motor + terminal on the controller to the Motor - terminal. This was simply to replicate the existence of "something" in the system at that position in the circuit. Once it was all back together (minus a few batteries) I found that there was no leak. I added the motor back in, the leak appeared.
I thought perhaps breaking the brushes in had created enough dust to cause the problem, so I decided to blow it out with compressed air. While some dust did come out, I could still measure the HV pack voltage on the chassis. Ghaaaa!!
It was time to contact George again. I can't express to you how much I did not want to darken his inbox with bad news again. George asked if I would send him and Tom Brunka of Helwig Carbon Brushes a picture of one of the brushes that I broke in. He wanted a close up of the face and shot of the profile. Puzzled, and unsure of how that would help, I obliged and sent off the photos. Tom got back and said that the brushes looked like they were broken in perfectly, so that was good. But then he apparently noticed something else, and that was the model number printed on the brush indicated it was for a 9" motor.
The pieces started falling into place for George at that point. The commutator on a 9" motor has a smaller circumference than that of an 11" motor. That means that the brushes for a 9" motor would be made with a smaller arc to the face. Aside for that, they are identical in function, composition and structure. But what that meant was that rather than the brush's surface resting with more or less complete contact on the commutator, it was riding on the very edges. That explained why they were so loud when I first put them in. Truthfully, at that time, I even wondered if I might have been sent brushes for a 9" motor, but it was just a passing thought.
So, through an innocent mistake, George had sent me the wrong brushes. He mentioned that it really was no problem to use them now that they were seated so well, and I would have had to wait another 2 weeks to get 11" brushes anyway. I was fine with keeping these. Anyway, because the brushes weren't contoured correctly for the 11" motor, that meant that a bit more material had to wear off of them than would have normally happened. Couple that with the fact that when running off a 12V battery, the motor doesn't spin fast enough to create enough airflow to vent the dust that does come off the brushes, and you have a recipe for developing and internal path to ground.
I went back and measured the resistance of the path from the motor terminal to the chassis and found that it was .880 mega Ohms. Don't ask me why I didn't measure that after I blew the motor out the first time, but I didn't think to. I saw that I could measure voltage on the chassis and felt that was enough of a problem that I didn't think to measure resistance. But what I found was that after I had blown it out, it had made a difference. .880 mega Ohms can only pass 0.13 milliamps at 160 volts. I could touch the terminal of the battery and the chassis and felt nothing.
George added that once I got the motor back on the road and spun it up to 3000 RPM, it would blow the rest of that dust out. he also mentioned that Warfield Electric consider a leak to chassis acceptable as long as it won't light up a light bulb. Well, .13 milliamps isn't enough to light a light bulb, and it's also not enough to cause my charger to complain.
Today I got everything back together, tested the systems, and flipped the charger on with fingers crossed. It came right on and dutifully charged the batteries back up to full. All systems go! I took the car down from the jack stands drove it out of the garage and put 20 miles on it this afternoon. It seemed like everyday since the car has been out of commission, I came across either a Nissan Leaf, or a Chevy Volt, while out driving and I would just grumble in envy. Today I saw Leaf while I was driving the Z3, and I simply felt joy.
Once I installed the new brushes and turned the motor on, it made a hell of a racket for the first few hours. I remember seeing a video John Allen had made when he was breaking in new brushes for his Warp 9, and I was struck by how loud it was, so I wasn't too surprised when mine made similar noises. I ran the motor for 100 hours and at the end, it sounded as smooth as silk. Job done!
I mounted the motor up to the transmission and tightened up all the bolts and called it a day, planning to reinstall the motor/transmission back into the car the next day. During the night, I realized I'd done something kind of stupid. The manual for the car states that you should put a little grease on the input shaft before you mate it up to the motor. It already had a film of grease on it, but I thought more is better. When thinking about it that evening, I realized that I had cleaned off a little grease I'd found on the flywheel. It was in a pattern that looked like it had been thrown off the shaft. It was at that point I realized more is not better, and I'd set myself up for a greasy, slip prone clutch. So I took the tranny off the motor, cleaned the shaft of excess grease and mounted it back up. It only took 45 minutes or so, so it wasn't that bad. I'm telling this story so that if anyone out there reading this can learn a lesson from my stupidity, then I've served some purpose on this planet.
Moving on. The motor/transmission assembly went in to the car later that day without a hitch, and thanks to my dad who came out to help me. I mounted up the drive line and started the process of re-assembling the car. It went quite smooth really. I was making one of the last battery connections when I leaned my elbow on the chassis, and it felt like I got stabbed or cut. I remember thinking that I didn't remember the bolt I leaned on being particularly sharp. I touched it again and realized that I didn't get stabbed, I got shocked. That's right my friends, the leak, which I was trying to get rid of, the one for which I'd been sent a replacement motor, was not gone.
Talk about a kick in the teeth. I started testing and dis-assembling everything and came to the conclusion that, once again, the source of the leak was in the motor. How could this be?!!! I was absolutely gutted and just walked away from the car for what ended up being the whole weekend while I thought about what to do.
I decided what I had to do was figure out, definitively if it was the motor or something else. I decided the best way to do that was to assemble all of the components completely, but leave the motor out of the assembly process. In place of the motor, I simply ran a cable from the Motor + terminal on the controller to the Motor - terminal. This was simply to replicate the existence of "something" in the system at that position in the circuit. Once it was all back together (minus a few batteries) I found that there was no leak. I added the motor back in, the leak appeared.
I thought perhaps breaking the brushes in had created enough dust to cause the problem, so I decided to blow it out with compressed air. While some dust did come out, I could still measure the HV pack voltage on the chassis. Ghaaaa!!
It was time to contact George again. I can't express to you how much I did not want to darken his inbox with bad news again. George asked if I would send him and Tom Brunka of Helwig Carbon Brushes a picture of one of the brushes that I broke in. He wanted a close up of the face and shot of the profile. Puzzled, and unsure of how that would help, I obliged and sent off the photos. Tom got back and said that the brushes looked like they were broken in perfectly, so that was good. But then he apparently noticed something else, and that was the model number printed on the brush indicated it was for a 9" motor.
The pieces started falling into place for George at that point. The commutator on a 9" motor has a smaller circumference than that of an 11" motor. That means that the brushes for a 9" motor would be made with a smaller arc to the face. Aside for that, they are identical in function, composition and structure. But what that meant was that rather than the brush's surface resting with more or less complete contact on the commutator, it was riding on the very edges. That explained why they were so loud when I first put them in. Truthfully, at that time, I even wondered if I might have been sent brushes for a 9" motor, but it was just a passing thought.
So, through an innocent mistake, George had sent me the wrong brushes. He mentioned that it really was no problem to use them now that they were seated so well, and I would have had to wait another 2 weeks to get 11" brushes anyway. I was fine with keeping these. Anyway, because the brushes weren't contoured correctly for the 11" motor, that meant that a bit more material had to wear off of them than would have normally happened. Couple that with the fact that when running off a 12V battery, the motor doesn't spin fast enough to create enough airflow to vent the dust that does come off the brushes, and you have a recipe for developing and internal path to ground.
I went back and measured the resistance of the path from the motor terminal to the chassis and found that it was .880 mega Ohms. Don't ask me why I didn't measure that after I blew the motor out the first time, but I didn't think to. I saw that I could measure voltage on the chassis and felt that was enough of a problem that I didn't think to measure resistance. But what I found was that after I had blown it out, it had made a difference. .880 mega Ohms can only pass 0.13 milliamps at 160 volts. I could touch the terminal of the battery and the chassis and felt nothing.
George added that once I got the motor back on the road and spun it up to 3000 RPM, it would blow the rest of that dust out. he also mentioned that Warfield Electric consider a leak to chassis acceptable as long as it won't light up a light bulb. Well, .13 milliamps isn't enough to light a light bulb, and it's also not enough to cause my charger to complain.
Today I got everything back together, tested the systems, and flipped the charger on with fingers crossed. It came right on and dutifully charged the batteries back up to full. All systems go! I took the car down from the jack stands drove it out of the garage and put 20 miles on it this afternoon. It seemed like everyday since the car has been out of commission, I came across either a Nissan Leaf, or a Chevy Volt, while out driving and I would just grumble in envy. Today I saw Leaf while I was driving the Z3, and I simply felt joy.
Wednesday, February 9, 2011
Balancing Act
For the past 4 months, I've been waiting for a break in the action so I could do a proper bottom balance on the battery pack. Well, the opportunity presented it's self this last week with some time off work and fewer than normal tasks that required my attention. But as fate is fickle, and sometimes cruel, I came down with a case of the flu which added a whole new level of unpleasantness to what was one of the most dull and tedious experiences I've had in recent memory.
A word on balancing; why do it? Strictly speaking, I supposed it's not necessary. However, it does provide you with a reference point about your battery's state which can be quite useful. All BMSs balance the batteries at the top of the charge. This, in an effort to make sure they are all fully charged and you get the most out of your batteries. But this is not without it's dangers. The alternative would be to balance the batteries at the bottom of the charge curve.
Try as you might to get a pack of batteries that are all identical, that's not going to happen. There will be variations in their capacity, however slight. What this means in practical terms is one of the batteries will either be charged to 100% before the rest, or discharged 100% before the rest. Without balancing, you can see both events could occur during one charge/discharge cycle even if one is careful. Since the real danger to these batteries is over charging or over discharging them, you've got danger at both ends of the spectrum. If you balance them to one end, you can make sure they all reach full at the same time, or they all reach 100% discharge at the same time, you've eliminated the danger on one side equation.
So now it becomes a question of where you want to balance the cells, top or bottom. Pick your poison as they both have their perils. The down side to top balancing is that you run the risk of having one or more cells hit rock bottom first during a discharge. If you aren't aware of it, and don't do anything about it, you'll drive the cell into reversal and kill it, followed by the next low cell. Generally considered bad. But in addition to that, you also have to trust that the BMS isn't going to malfunction at the top of the charge and let one or more cells run too high. Also bad, and there are multiple incidents of this occurring resulting in fires, wholesale destruction of the car and anything near it.
Bottom balancing means you make sure all the cells hit bottom at the same time. The advantage is you're not going to kill one or more cells due to imbalance at the bottom. The disadvantage is that you must set your charging algorithm up to accommodate the imbalance at the top. This, as we'll see, is easy and only has to be done once. So, we have a choice fraught with danger during every charge and every discharge, or one that needs care in setting up and then no down side. The choice seems obvious to me.
The goal was to take every cell down below 2.74 volts. The CALB batteries are considered dead at 2.0 volts, but the difference between 2.0 and 2.74, in terms of the amount of power stored in the cell, is trivial. In addition, 2.74 is over the knee on the discharge curve and a hop away from dead. Once at 2.74, I intended to charge them back up to 2.750 volts. Once they were all even, charge them. Seems simple right? In concept, it is. Executing the plan proved to be a bit more challenging.
Let's take a look at the tools of the trade:
At the bottom of the picture is the DVM, or digital volt meter. No surprise there, any self respecting person should own one of these. This one is accurate to 1/1000th of a volt. Well, it displays to 1/1000th of a volt, but I have no idea how accurate it is. I do, however, believe that it is consistent. So even if it's off in it's readings just a bit, it's off the same amount on every reading, so that will do. Just above that and to either side of the photo are two very sophisticated pieces of equipment used to draw power out of the batteries, otherwise known as automotive lamps. Others may use a more elaborate and expensive piece of equipment, and they are probably very useful, but I don't have anything like that, so lamps it is. Above those and at the top of the picture is what's commonly called a bench power supply. This little device can put out any voltage between 0 and 18 volts and any current between 0 and 3 amps. I'll use that to charge individual cells.
I had gone for a particularly long drive and I'd used about 98 of the 120 amp/hours the batteries hold. I decided to take a few laps around the neighborhood, and once I'd drawn out a total of 115 amp/hours, I pulled into the garage. I then measured every battery and found the 4 lowest cells. They were each just over 3.0 volts. I turned the car on, turned the heater on, got my DVM ready and started measuring. I kept my eye on all the cells, but paid particular attention to the 4 lowest ones. It became clear in a short period of time which one was dropping first so I focused my attention on that one. By the time it got to 2.74 volts, there were still several other cells right near 3.0 volts. I decided to add some current to that one cell and get it up to 2.9 volts. It took about 10 to 12 minutes, with the bench power supply set at 3 volts and 3 amps. That worked out pretty well, so I turned the heater back on to bring them all down.
By the time that cell reached 2.70 volts, a few others were just below 2.75 with the rest in the 2.8's and 2.9's. I would need to draw the power out of those individually. But when it was all said and done, the 120 amp/hour CALB cells had given up 127.5 amp/hours of current. Not bad, not bad at all. I threw the big red switch isolating the battery pack from the car and began working.
I went through all the batteries again, recording the voltage on each. At that point, I began identifying which needed some extra power pulled out and how much I'd need to pull out. Starting with the first battery in the pack, I clipped the lights to the terminals and watched with the DVM. The lights issued a nice warm glow as they ate up the power. When the DVM read 2.65 volts, I unplugged the lights. The meter immediately began to rise and within 5 minutes it was over 2.75. Ok, so 2.65 wouldn't do, how about 2.60? That showed more promise, and I proceeded through about 5 batteries in this manner.
It was very slow going as it took anywhere from 15 to 30 minutes to drain each battery. But then I realized that I could do more than one at a time if they were adjacent to each other in the series. At that point, I started working in groups of 2, 3 or 4 batteries at a time. The more batteries I hooked up to the lamps, the brighter they glowed. Worked perfect.
What didn't work perfectly, or I should say, what I didn't expect was how much the batteries would recover after I got them down to the 2.74 mark. It took me two days work, to get through all the batteries. When I'd finally got the last one down, just below 2.74, I went back and started measuring the cells at the front of the pack, only to find that they'd recovered and were now all hovering around 2.76 to 2.82 volts. Ok, this was going to require another pass through the whole pack taking them down perhaps a tad further. But before I did that, I decided to run a quick test. I worked with the first 4 batteries, and recorded the voltage of each. I decided that I would leave the lamps on the battery for 10 seconds, plus 5 seconds for every 1/1000th of a volt over the target. Once I was done drawing off the power I left them over night and came back to measure them in the morning.
The next day, with the flu in full swing now, I dragged myself out to the garage and took measurements on those cells. Each was between 2.74 and 2.75. That did it!! Next I simply had to work my way through the rest of the pack. That took a few hours, but as I'd learned, I had to let them rest for a while before I could get an accurate reading off them. Since I felt horrible and was in danger of covering every battery with plegm, I decided to call it a day and start fresh in the morning.
Next morning they all looked perfect. Now came time to carefully charge each up to the 2.750 target I was looking for. The short story here is that I got the first 18 or so to that target voltage, and went in for the night. I basically charged them up to 2.83 volts each and watch them settle back to 2.750. However the next day when I came out to continue with the remaining 30 cells, I'd found that all the batteries that had been at 2.750 had crept up and were all over the place. The lowest was at 2.758, the highest at 2.810. What the...
This is when the notes I'd been taking became very useful. I found that the ones that had crept the highest were the ones that were on the charger the longest. Even though a particular cell might have settled to 2.750, if it took more energy to get it there, while resting over night the voltage climbed higher than one that had needed less energy to get it to the target.
So what was the magic formula? I can't really tell you because as I worked I got more in tune with the batteries and what they needed. It really was a very touchy-feely operation. But I can tell you with conviction that what brought me success was recording everything I did and how the batteries reacted to them. I could start recognizing patterns and figure out how they would react to any given charge or discharge. Plus, you simply must give the batteries time to settle once you've worked with them; 6 hours is good, 12 is better.
What I also found was that getting the cells to 2.750 volts at 11:30 at night when it's cold means that they will rise to 2.756 or so when the day warms up. I can also tell you that getting them all to the same 1/1000th of a volt proved more of a challenge that I was willing to endure. I settled for a spread across 2 1/1000th's of a volt. I'd say that's acceptable in anyone's book. So yesterday morning, I took measurements of all the cells and found, after they'd rested all night, that every cell was 2.752 or 2.753 volts. The entire pack measured 132.1 volts. Time to charge.
I was particularly interested to see how much current they'd accept at this point. I threw the big red switch connecting the pack to the car and the charger, plugged in and ramped up the current. I set the charger for the highest setting it can muster and it was putting out 29.0 amps. That went on for three hours, when the voltage got high enough that the charger said "we're done" and shut off. Well, I knew we weren't done and I expected that. Those who've read my experiences from last September and the lessons I learned from Ohm's law will remember. I hadn't touched the voltage potentiometer on the charger, so it was reading a higher voltage than the normal shutoff voltage I've selected since I'd set it for more of a lower 15 amp charge. Increase the amps to the batteries, resistance goes up, consequently voltage to push that current goes up and the charger reads that as a full pack and shuts off early.
This was all fine and anticipated. I turned the charger back on and turned the current down to 20 amps. About 2.5 hours later the charger started to tell me it was near done. I measure each of the batteries and found that they were anywhere from 3.390 and 3.43 volts. I wrote down the four cells that were highest with the intentions of watching them carefully until the end of the charge.
I turned the charger off, turned the current knob down and started it back up again. This time I turned it to 15 amps, which would be a full charge on the batteries before I'd done the balancing. I wasn't sure how much time was going to pass before they were done, but I needed to stay with them, measuring the whole time to be sure no cells went over. As the batteries approached their normal cutoff voltage of 164.7 I'd set the charger for I was measuring every cell in the pack, starting at the front, working my way through them and starting over. What I found was that the 4 I'd originally ID'd as showing a bit higher voltage remained slightly higher of the others the whole way. That is until just right before the charger reached it's cutoff when one cell stuck it's head up and hit 3.45 volts before any other. Five minutes later, the charger indicated that it was going into constant voltage mode and started to ramp down the current.
No cell went over 3.46 volts, well shy of the 3.6 CALB states is the top end. In fact the highest cell went to 3.48 volts. That leaves me plenty of wiggle room between the charger's cutoff and the top of the batteries. When all was said and done, the batteries had accepted 119 amp/hours. That's 1 amp/hour shy of their reported capacity and a full 8.5 shy of their demonstrated capacity. But I'm fine with that because that means I can plug the car in, walk away, and remain confident that batteries will charge up to near their full capacity and not burn down my car or house. That said, I don't intend to do that for a few cycles. Not until I'm sure I'm seeing consistent behavior from all the cells.
There you have it. I hope it wasn't as tedious to read as it was to experience, and I hope it offers some information to others planning the same thing. In a few months, I'll run the batteries down again and see how well they've done staying in balance relative to each other. Should be interesting.
A word on balancing; why do it? Strictly speaking, I supposed it's not necessary. However, it does provide you with a reference point about your battery's state which can be quite useful. All BMSs balance the batteries at the top of the charge. This, in an effort to make sure they are all fully charged and you get the most out of your batteries. But this is not without it's dangers. The alternative would be to balance the batteries at the bottom of the charge curve.
Try as you might to get a pack of batteries that are all identical, that's not going to happen. There will be variations in their capacity, however slight. What this means in practical terms is one of the batteries will either be charged to 100% before the rest, or discharged 100% before the rest. Without balancing, you can see both events could occur during one charge/discharge cycle even if one is careful. Since the real danger to these batteries is over charging or over discharging them, you've got danger at both ends of the spectrum. If you balance them to one end, you can make sure they all reach full at the same time, or they all reach 100% discharge at the same time, you've eliminated the danger on one side equation.
So now it becomes a question of where you want to balance the cells, top or bottom. Pick your poison as they both have their perils. The down side to top balancing is that you run the risk of having one or more cells hit rock bottom first during a discharge. If you aren't aware of it, and don't do anything about it, you'll drive the cell into reversal and kill it, followed by the next low cell. Generally considered bad. But in addition to that, you also have to trust that the BMS isn't going to malfunction at the top of the charge and let one or more cells run too high. Also bad, and there are multiple incidents of this occurring resulting in fires, wholesale destruction of the car and anything near it.
Bottom balancing means you make sure all the cells hit bottom at the same time. The advantage is you're not going to kill one or more cells due to imbalance at the bottom. The disadvantage is that you must set your charging algorithm up to accommodate the imbalance at the top. This, as we'll see, is easy and only has to be done once. So, we have a choice fraught with danger during every charge and every discharge, or one that needs care in setting up and then no down side. The choice seems obvious to me.
The goal was to take every cell down below 2.74 volts. The CALB batteries are considered dead at 2.0 volts, but the difference between 2.0 and 2.74, in terms of the amount of power stored in the cell, is trivial. In addition, 2.74 is over the knee on the discharge curve and a hop away from dead. Once at 2.74, I intended to charge them back up to 2.750 volts. Once they were all even, charge them. Seems simple right? In concept, it is. Executing the plan proved to be a bit more challenging.
Let's take a look at the tools of the trade:
At the bottom of the picture is the DVM, or digital volt meter. No surprise there, any self respecting person should own one of these. This one is accurate to 1/1000th of a volt. Well, it displays to 1/1000th of a volt, but I have no idea how accurate it is. I do, however, believe that it is consistent. So even if it's off in it's readings just a bit, it's off the same amount on every reading, so that will do. Just above that and to either side of the photo are two very sophisticated pieces of equipment used to draw power out of the batteries, otherwise known as automotive lamps. Others may use a more elaborate and expensive piece of equipment, and they are probably very useful, but I don't have anything like that, so lamps it is. Above those and at the top of the picture is what's commonly called a bench power supply. This little device can put out any voltage between 0 and 18 volts and any current between 0 and 3 amps. I'll use that to charge individual cells.
I had gone for a particularly long drive and I'd used about 98 of the 120 amp/hours the batteries hold. I decided to take a few laps around the neighborhood, and once I'd drawn out a total of 115 amp/hours, I pulled into the garage. I then measured every battery and found the 4 lowest cells. They were each just over 3.0 volts. I turned the car on, turned the heater on, got my DVM ready and started measuring. I kept my eye on all the cells, but paid particular attention to the 4 lowest ones. It became clear in a short period of time which one was dropping first so I focused my attention on that one. By the time it got to 2.74 volts, there were still several other cells right near 3.0 volts. I decided to add some current to that one cell and get it up to 2.9 volts. It took about 10 to 12 minutes, with the bench power supply set at 3 volts and 3 amps. That worked out pretty well, so I turned the heater back on to bring them all down.
By the time that cell reached 2.70 volts, a few others were just below 2.75 with the rest in the 2.8's and 2.9's. I would need to draw the power out of those individually. But when it was all said and done, the 120 amp/hour CALB cells had given up 127.5 amp/hours of current. Not bad, not bad at all. I threw the big red switch isolating the battery pack from the car and began working.
I went through all the batteries again, recording the voltage on each. At that point, I began identifying which needed some extra power pulled out and how much I'd need to pull out. Starting with the first battery in the pack, I clipped the lights to the terminals and watched with the DVM. The lights issued a nice warm glow as they ate up the power. When the DVM read 2.65 volts, I unplugged the lights. The meter immediately began to rise and within 5 minutes it was over 2.75. Ok, so 2.65 wouldn't do, how about 2.60? That showed more promise, and I proceeded through about 5 batteries in this manner.
It was very slow going as it took anywhere from 15 to 30 minutes to drain each battery. But then I realized that I could do more than one at a time if they were adjacent to each other in the series. At that point, I started working in groups of 2, 3 or 4 batteries at a time. The more batteries I hooked up to the lamps, the brighter they glowed. Worked perfect.
What didn't work perfectly, or I should say, what I didn't expect was how much the batteries would recover after I got them down to the 2.74 mark. It took me two days work, to get through all the batteries. When I'd finally got the last one down, just below 2.74, I went back and started measuring the cells at the front of the pack, only to find that they'd recovered and were now all hovering around 2.76 to 2.82 volts. Ok, this was going to require another pass through the whole pack taking them down perhaps a tad further. But before I did that, I decided to run a quick test. I worked with the first 4 batteries, and recorded the voltage of each. I decided that I would leave the lamps on the battery for 10 seconds, plus 5 seconds for every 1/1000th of a volt over the target. Once I was done drawing off the power I left them over night and came back to measure them in the morning.
The next day, with the flu in full swing now, I dragged myself out to the garage and took measurements on those cells. Each was between 2.74 and 2.75. That did it!! Next I simply had to work my way through the rest of the pack. That took a few hours, but as I'd learned, I had to let them rest for a while before I could get an accurate reading off them. Since I felt horrible and was in danger of covering every battery with plegm, I decided to call it a day and start fresh in the morning.
Next morning they all looked perfect. Now came time to carefully charge each up to the 2.750 target I was looking for. The short story here is that I got the first 18 or so to that target voltage, and went in for the night. I basically charged them up to 2.83 volts each and watch them settle back to 2.750. However the next day when I came out to continue with the remaining 30 cells, I'd found that all the batteries that had been at 2.750 had crept up and were all over the place. The lowest was at 2.758, the highest at 2.810. What the...
This is when the notes I'd been taking became very useful. I found that the ones that had crept the highest were the ones that were on the charger the longest. Even though a particular cell might have settled to 2.750, if it took more energy to get it there, while resting over night the voltage climbed higher than one that had needed less energy to get it to the target.
So what was the magic formula? I can't really tell you because as I worked I got more in tune with the batteries and what they needed. It really was a very touchy-feely operation. But I can tell you with conviction that what brought me success was recording everything I did and how the batteries reacted to them. I could start recognizing patterns and figure out how they would react to any given charge or discharge. Plus, you simply must give the batteries time to settle once you've worked with them; 6 hours is good, 12 is better.
What I also found was that getting the cells to 2.750 volts at 11:30 at night when it's cold means that they will rise to 2.756 or so when the day warms up. I can also tell you that getting them all to the same 1/1000th of a volt proved more of a challenge that I was willing to endure. I settled for a spread across 2 1/1000th's of a volt. I'd say that's acceptable in anyone's book. So yesterday morning, I took measurements of all the cells and found, after they'd rested all night, that every cell was 2.752 or 2.753 volts. The entire pack measured 132.1 volts. Time to charge.
I was particularly interested to see how much current they'd accept at this point. I threw the big red switch connecting the pack to the car and the charger, plugged in and ramped up the current. I set the charger for the highest setting it can muster and it was putting out 29.0 amps. That went on for three hours, when the voltage got high enough that the charger said "we're done" and shut off. Well, I knew we weren't done and I expected that. Those who've read my experiences from last September and the lessons I learned from Ohm's law will remember. I hadn't touched the voltage potentiometer on the charger, so it was reading a higher voltage than the normal shutoff voltage I've selected since I'd set it for more of a lower 15 amp charge. Increase the amps to the batteries, resistance goes up, consequently voltage to push that current goes up and the charger reads that as a full pack and shuts off early.
This was all fine and anticipated. I turned the charger back on and turned the current down to 20 amps. About 2.5 hours later the charger started to tell me it was near done. I measure each of the batteries and found that they were anywhere from 3.390 and 3.43 volts. I wrote down the four cells that were highest with the intentions of watching them carefully until the end of the charge.
I turned the charger off, turned the current knob down and started it back up again. This time I turned it to 15 amps, which would be a full charge on the batteries before I'd done the balancing. I wasn't sure how much time was going to pass before they were done, but I needed to stay with them, measuring the whole time to be sure no cells went over. As the batteries approached their normal cutoff voltage of 164.7 I'd set the charger for I was measuring every cell in the pack, starting at the front, working my way through them and starting over. What I found was that the 4 I'd originally ID'd as showing a bit higher voltage remained slightly higher of the others the whole way. That is until just right before the charger reached it's cutoff when one cell stuck it's head up and hit 3.45 volts before any other. Five minutes later, the charger indicated that it was going into constant voltage mode and started to ramp down the current.
No cell went over 3.46 volts, well shy of the 3.6 CALB states is the top end. In fact the highest cell went to 3.48 volts. That leaves me plenty of wiggle room between the charger's cutoff and the top of the batteries. When all was said and done, the batteries had accepted 119 amp/hours. That's 1 amp/hour shy of their reported capacity and a full 8.5 shy of their demonstrated capacity. But I'm fine with that because that means I can plug the car in, walk away, and remain confident that batteries will charge up to near their full capacity and not burn down my car or house. That said, I don't intend to do that for a few cycles. Not until I'm sure I'm seeing consistent behavior from all the cells.
There you have it. I hope it wasn't as tedious to read as it was to experience, and I hope it offers some information to others planning the same thing. In a few months, I'll run the batteries down again and see how well they've done staying in balance relative to each other. Should be interesting.
Thursday, October 7, 2010
The Charger Has Returned Home
The charger arrived back from Manzanita Micro today, safe, sound and in perfect working order. They received it last Thursday, and had it fixed and on it's way back to me by Monday. I found out that it was the AC rectifier bridge that I'd damaged. They repaired that and then fully tested the unit to make sure it was healthy in all respects. The grand total in charges... $125, and $50 of that was shipping. How great is that!? I seriously hope I never have to send it back, but if I do, I know it's in great hands.
I got it back and began re-assembling the car. I hadn't done too much to it, so it only took me an hour or so. It was with some trepidation that I threw the switch to start charging the car. But it turned out my concerns were not needed. It fired up and started working like a dream.
I would still like to install the inrush limiters, or thermistors on the DC to DC converters. I bought a little project box, meaning to do it during this week's down time. But I found out more about they way they work which forced me to change my plans. When cold, they offer high resistance to the current, which keeps the arcing to a minimum, but they quickly heat up as current flows through them and the resistance drops. It's not unusual for them to reach 200° F. Well the project box I bought was plastic, so that wouldn't do. But worse, the only place I have to mount them is against the plastic box in the trunk that holds the charger and DC to DC converters.
So, I need to re-think how I'm going to do that, and where I'm going to mount them. I'm kind of at a loss right now, but I'll figure something out eventually. I could disassemble the DC to DC converters and actually put them inside the housing, but I really don't want to do that. Regardless, tomorrow I'm back on the road with a nice big EV grin!
COMPLETELY OFF TOPIC
A friend of mine named Fred and I have launched a new blog. It is called F1-Geeks, and as you might have guessed, it's devoted to Formula 1. But that's not all! We actually intend to talk about several topics that we and others like us find particularly interesting; cars, gaming, tech gadgets, home theater stuff and EV stuff too. Check it out, and leave us a comment or two if you feel like it. Thanks!
I got it back and began re-assembling the car. I hadn't done too much to it, so it only took me an hour or so. It was with some trepidation that I threw the switch to start charging the car. But it turned out my concerns were not needed. It fired up and started working like a dream.
I would still like to install the inrush limiters, or thermistors on the DC to DC converters. I bought a little project box, meaning to do it during this week's down time. But I found out more about they way they work which forced me to change my plans. When cold, they offer high resistance to the current, which keeps the arcing to a minimum, but they quickly heat up as current flows through them and the resistance drops. It's not unusual for them to reach 200° F. Well the project box I bought was plastic, so that wouldn't do. But worse, the only place I have to mount them is against the plastic box in the trunk that holds the charger and DC to DC converters.
So, I need to re-think how I'm going to do that, and where I'm going to mount them. I'm kind of at a loss right now, but I'll figure something out eventually. I could disassemble the DC to DC converters and actually put them inside the housing, but I really don't want to do that. Regardless, tomorrow I'm back on the road with a nice big EV grin!
COMPLETELY OFF TOPIC
A friend of mine named Fred and I have launched a new blog. It is called F1-Geeks, and as you might have guessed, it's devoted to Formula 1. But that's not all! We actually intend to talk about several topics that we and others like us find particularly interesting; cars, gaming, tech gadgets, home theater stuff and EV stuff too. Check it out, and leave us a comment or two if you feel like it. Thanks!
Monday, September 27, 2010
Chargers Away
One of the tough things about building this car was the extremely tight spaces I had to work with and in. Getting my arms back there to turn the screws and bolts that held the charger in was so difficult. It took me the better part of an hour, but I finally liberated the charger from it's home.
Here's the charger, which looks totally fine.
I packaged it up very carefully and handed it to UPS this afternoon. In an email exchange with Rich from Manzanita, he said that assuming nothing other than the input AC rectifier is damaged, they should be able to fix it up in a day or two for around $200. How great is that?!
As I've mentioned before, I need to raise the height of the front of the car. I found a place that will build new springs for me, but they want one of the springs and some measurements off of the front suspension. Well, I can't take a spring off the car and mail it away, I'm using them at the moment. While looking around on eBay for a spare spring I can send off to Kansas, I came across an item that I had always felt sure must have existed, but I'd never seen. A quick search in Google and I found these items.
These are spacers that you can slip between the coils of a spring to give it up to a 1" lift. The springs on the Z3 were already riding low when I bought the car. The car was riding about 3/4" lower than stock. With the extra weight of the batteries and motor, it dropped another 3/4".
I took a look at the springs and the bottom 2 coils were very close to each other. I jacked the car up one side at a time and slipped them in, wedging them as far down in the coil as I could. I sat the car back down, drove it around a bit and then measured the ride height. It gained 2cm, or .79". That's more than I lost from doing the conversion. It looks much better too.
Of course that means I've lost a bit of spring travel, but not 2 cm since the gap I squeezed the rubber piece into was more like 1 cm high when the car was on the ground. The real question is will that loss of 1 cm of spring travel cause me problems. I don't think it will, I already drive it very carefully and slowly over bumps. But it's the bumps you don't see that get you. The good thing is that if the spring should collapse all the way, that big grommet is rubber and will flex. Hopefully enough to protect the pillar.
I think it's a good band-aid solution, but I'm going to continue my efforts to get the car sprung properly.
Here's the charger, which looks totally fine.
I packaged it up very carefully and handed it to UPS this afternoon. In an email exchange with Rich from Manzanita, he said that assuming nothing other than the input AC rectifier is damaged, they should be able to fix it up in a day or two for around $200. How great is that?!
As I've mentioned before, I need to raise the height of the front of the car. I found a place that will build new springs for me, but they want one of the springs and some measurements off of the front suspension. Well, I can't take a spring off the car and mail it away, I'm using them at the moment. While looking around on eBay for a spare spring I can send off to Kansas, I came across an item that I had always felt sure must have existed, but I'd never seen. A quick search in Google and I found these items.
These are spacers that you can slip between the coils of a spring to give it up to a 1" lift. The springs on the Z3 were already riding low when I bought the car. The car was riding about 3/4" lower than stock. With the extra weight of the batteries and motor, it dropped another 3/4".
I took a look at the springs and the bottom 2 coils were very close to each other. I jacked the car up one side at a time and slipped them in, wedging them as far down in the coil as I could. I sat the car back down, drove it around a bit and then measured the ride height. It gained 2cm, or .79". That's more than I lost from doing the conversion. It looks much better too.
Of course that means I've lost a bit of spring travel, but not 2 cm since the gap I squeezed the rubber piece into was more like 1 cm high when the car was on the ground. The real question is will that loss of 1 cm of spring travel cause me problems. I don't think it will, I already drive it very carefully and slowly over bumps. But it's the bumps you don't see that get you. The good thing is that if the spring should collapse all the way, that big grommet is rubber and will flex. Hopefully enough to protect the pillar.
I think it's a good band-aid solution, but I'm going to continue my efforts to get the car sprung properly.
Thursday, September 23, 2010
Something Stupid
Just when everything is going well...
I've been making slow progress zeroing in on getting the charger set to bring the batteries up to the optimal charge point before it turns off. It's tough because the charger uses a little screw potentiometer to adjust it up and down. It's exceedingly difficult to get it right where you want it. Plus I've found that if you change the current you're pushing to the pack, the high voltage point at which the charger believes it's done changes.
When I have the charger turned up all the way so that it's pushing 28 amps, it would cut off at 164.5 volts. But if I ramp the current down to 10 amps, it trips off at 165.8 volts. It would be so much nicer if the charger had a digital interface for setting the cut off voltage. I realize that would add to the cost of the charger, but I have to tell you, I'd pay for it.
This morning I was charging the car at 10 amps The charger hit it's limit threshold at 164.7, which is about where I want it. I started taking measurements on the cells to monitor how they were doing. There are a couple that come up to 3.6 volts faster than the others. While measuring one of the cells I slipped and touched the probe to the chassis while it was on the positive terminal for that cell. Well, there was a loud pop, and a nice bright flash. When I looked down, the point on the end of my probe had been melted to a nice rounded blob, the terminal had a big black spot around it, and the charger had flipped off.
I checked everything and couldn't find any obvious problems to any of the systems. I tried to turn the charger back on, but there was no power to the charger; the breaker for the outlet had popped too. I reset it and tried to turn the charger on again. Loud pop, but no flash anywhere, and the charger tripped it's breaker and the breaker on the house tripped too. *Sigh*
So it would seem that through clumsiness or carelessness, I've damaged my charger. I've sent an email off to Rich Rudman at Manzanita Micro to get his advice. But I'm pretty sure that the chargers coming out of the car soon and making a trip to Washington. Man I hate it when I do stupid stuff. And just as the weather is really getting beautiful for top down driving! *Sigh*
UPDATE:
I heard back from Rich at Manzanita. Apparently I've blown the input AC rectifier. So, I'll be taking the charger out of the car ASAP and sending it back to them for repair.
I've been making slow progress zeroing in on getting the charger set to bring the batteries up to the optimal charge point before it turns off. It's tough because the charger uses a little screw potentiometer to adjust it up and down. It's exceedingly difficult to get it right where you want it. Plus I've found that if you change the current you're pushing to the pack, the high voltage point at which the charger believes it's done changes.
When I have the charger turned up all the way so that it's pushing 28 amps, it would cut off at 164.5 volts. But if I ramp the current down to 10 amps, it trips off at 165.8 volts. It would be so much nicer if the charger had a digital interface for setting the cut off voltage. I realize that would add to the cost of the charger, but I have to tell you, I'd pay for it.
This morning I was charging the car at 10 amps The charger hit it's limit threshold at 164.7, which is about where I want it. I started taking measurements on the cells to monitor how they were doing. There are a couple that come up to 3.6 volts faster than the others. While measuring one of the cells I slipped and touched the probe to the chassis while it was on the positive terminal for that cell. Well, there was a loud pop, and a nice bright flash. When I looked down, the point on the end of my probe had been melted to a nice rounded blob, the terminal had a big black spot around it, and the charger had flipped off.
I checked everything and couldn't find any obvious problems to any of the systems. I tried to turn the charger back on, but there was no power to the charger; the breaker for the outlet had popped too. I reset it and tried to turn the charger on again. Loud pop, but no flash anywhere, and the charger tripped it's breaker and the breaker on the house tripped too. *Sigh*
So it would seem that through clumsiness or carelessness, I've damaged my charger. I've sent an email off to Rich Rudman at Manzanita Micro to get his advice. But I'm pretty sure that the chargers coming out of the car soon and making a trip to Washington. Man I hate it when I do stupid stuff. And just as the weather is really getting beautiful for top down driving! *Sigh*
UPDATE:
I heard back from Rich at Manzanita. Apparently I've blown the input AC rectifier. So, I'll be taking the charger out of the car ASAP and sending it back to them for repair.
Tuesday, February 16, 2010
Charger Set Up and More
Well, after the initial test, and after the excitement passed of seeing the wheels spin, it was time to get back to work so I can actually get the car out of the garage.
Here's a quick rundown.
To keep them safe, and extend their lives, I've opted for a target charge of 3.5 Volts per battery; times 48 batteries equals 168 Volts. I didn't come up with this value on my own, I learned a great deal from Jack Rickard and his web site: EVTV.ME . Jack has done a hell of a job exploring the limits of these batteries, posting the results and explaining what he's learned from doing so.
So with the target of 168 Volts, I plugged in the car and started pushing some current to the batteries. The charger can read the pack voltage, and it has a potentiometer that allows you to set the voltage you're pushing. Once the pack reaches the voltage you want, you turn the potentiometer down until a light comes on. That indicates the target voltage has been reached and the charger goes into a timer mode and backs down the current until it switches off.
The whole endeavor took 5 hours, with me checking voltage every 5 minutes to be sure I didn't miss the target. It was a long day, but I got the charger set, and I only had to do it once.
I ordered a replacement for the stock tachometer. I fiddled with it for an hour and couldn't make it move at all. It's too bad, I really wanted the stock look. But I found a place on line that makes custom ones, with what ever color numbers printed that you want, what ever background light, a number of fonts to choose from etc. And it was very reasonable at $120. The bad news is 7 days before it ships.
More tomorrow!
Here's a quick rundown.
- Ran power from the main battery pack to the DC to DC converters
- Hooked the DC to DC converters up to the auxiliary battery
- Tested the output of the converters while car is off and while it's running
- Installed all the inline fuses for the Zilla controller and Link 10 meter
- Connected the reverse lights to the reverse switch in the transmission
- Went through the menus and set up the Link 10 meter
- Went through the Zilla's configuration menu and set that up
- Cut and refit all the carpet and plastic parts for the trunk
- Checked the air pressure on all the tires, set them all to 40 PSI
- Charged the batteries completely and set up the charger
To keep them safe, and extend their lives, I've opted for a target charge of 3.5 Volts per battery; times 48 batteries equals 168 Volts. I didn't come up with this value on my own, I learned a great deal from Jack Rickard and his web site: EVTV.ME . Jack has done a hell of a job exploring the limits of these batteries, posting the results and explaining what he's learned from doing so.
So with the target of 168 Volts, I plugged in the car and started pushing some current to the batteries. The charger can read the pack voltage, and it has a potentiometer that allows you to set the voltage you're pushing. Once the pack reaches the voltage you want, you turn the potentiometer down until a light comes on. That indicates the target voltage has been reached and the charger goes into a timer mode and backs down the current until it switches off.
The whole endeavor took 5 hours, with me checking voltage every 5 minutes to be sure I didn't miss the target. It was a long day, but I got the charger set, and I only had to do it once.
I ordered a replacement for the stock tachometer. I fiddled with it for an hour and couldn't make it move at all. It's too bad, I really wanted the stock look. But I found a place on line that makes custom ones, with what ever color numbers printed that you want, what ever background light, a number of fonts to choose from etc. And it was very reasonable at $120. The bad news is 7 days before it ships.
More tomorrow!
Monday, February 15, 2010
Odds & Ends Part XI
Let's start with a list of things I did today...
Here's a shot of the breaker and the shunt to the right and above it. As I was running all the wires to those two, I realized that there was no safe way to get all those wires in place while the batteries on the right side of the picture were in place. So, I had to disassemble the pack in that box to get that work done.
Here's a shot of the fuse I installed today. That fuse can easily handle the 1000 amps I could draw from the battery pack. But it would blow quickly in the event of a dead short.
Here's the zilla controller at the bottom of the frame, and the hairball at the top. I think I've got all the components wired to it at this point. In fact, I think I'm ready to test the system and see if I can spin the wheels. But before I do, I think I'll go over the wiring of each item, just to make sure I haven't made any bone-headed mistakes.
- Installed high voltage (HV) fuse
- Ran +HV line from trunk to fuse
- Ran +HV line from fuse to breaker
- Ran -HV line from trunk to forward batteries
- Ran -HV line from shunt to controller
- Ran +HV line from breaker to contactor
- Re-routed signal wires away from HV cables
- Attached all signal wires for the Link10 monitor
- Attached throttle control wires to the Zilla controller
- Attached the RPM sensor wires to the Zilla
- Connected the hairball (Zilla's brain) to the Zilla controller
- Attached wires for heater to the battery
- Attached charger to the battery
Here's a shot of the breaker and the shunt to the right and above it. As I was running all the wires to those two, I realized that there was no safe way to get all those wires in place while the batteries on the right side of the picture were in place. So, I had to disassemble the pack in that box to get that work done.
Here's a shot of the fuse I installed today. That fuse can easily handle the 1000 amps I could draw from the battery pack. But it would blow quickly in the event of a dead short.
Here's the zilla controller at the bottom of the frame, and the hairball at the top. I think I've got all the components wired to it at this point. In fact, I think I'm ready to test the system and see if I can spin the wheels. But before I do, I think I'll go over the wiring of each item, just to make sure I haven't made any bone-headed mistakes.
Thursday, November 12, 2009
Ignition Switch
The Zilla controller requires two leads from the ignition switch. One that has power when the key is turned to the "Start" position, and the other when the key is in the "Run" position. Today, I thought I'd look into isolating each lead and running an attached line to the electrics bay.
The "Start" position lead was easy to locate. I spliced a new 18 gauge wire to it and ran that to where the Zilla will sit. For whatever reason, the "Run" position lead was much harder to locate. So much so, I haven't found it.
The ignition switch has 4 positions, Off, Accessory, Run and Start. There are 6 lines running to the back of the switch. One of the lines gets power when ever the car has been started, and power is sent to it even after you turn the car off. Only pulling the key removes power to that line. I certainly don't want the car to run until I pull the key out. None of the other leads change state when you move the key through the positions. Now, granted, I've been testing this with a simple continuity test using the power feed and the other lines. I'm thinking that I'm just going to have to wait until I can run power to the switch and measure voltage across each terminal.
I also ran power out to the switch in the fuel door. You may remember that switch will keep the car from starting up when the fuel door is open and the car is charging. That's it for today. Two more things checked off the list.
The "Start" position lead was easy to locate. I spliced a new 18 gauge wire to it and ran that to where the Zilla will sit. For whatever reason, the "Run" position lead was much harder to locate. So much so, I haven't found it.
The ignition switch has 4 positions, Off, Accessory, Run and Start. There are 6 lines running to the back of the switch. One of the lines gets power when ever the car has been started, and power is sent to it even after you turn the car off. Only pulling the key removes power to that line. I certainly don't want the car to run until I pull the key out. None of the other leads change state when you move the key through the positions. Now, granted, I've been testing this with a simple continuity test using the power feed and the other lines. I'm thinking that I'm just going to have to wait until I can run power to the switch and measure voltage across each terminal.
I also ran power out to the switch in the fuel door. You may remember that switch will keep the car from starting up when the fuel door is open and the car is charging. That's it for today. Two more things checked off the list.
Friday, October 2, 2009
Odds & Ends Part VI
Today was a day to take care of some smaller things.
I cut a hole in the trunk's battery box and mounted the ventilation tubing in it. I also ran the tubing to the fan mounted under the box that occupies the space where the gas tank was. I routed the tubing where I need it to go and secured it to the under side of the chassis so it doesn't move around and run into the suspension.
I also secured the wire loom that had been hanging in the trunk to the box mentioned above. Here's a shot of the trunk as it is now.
Notice the nice clean appearance, and the tubing inlet in the lower left corner of the picture.
I marked and drilled several holes in the tray that will hold the Zilla controller. Once I sort out the position of all the other electrical components, I'll be able to just mount the Zilla to it and then drop the tray in place and bolt it down.
That's all for now, back next week.
I cut a hole in the trunk's battery box and mounted the ventilation tubing in it. I also ran the tubing to the fan mounted under the box that occupies the space where the gas tank was. I routed the tubing where I need it to go and secured it to the under side of the chassis so it doesn't move around and run into the suspension.
I also secured the wire loom that had been hanging in the trunk to the box mentioned above. Here's a shot of the trunk as it is now.
Notice the nice clean appearance, and the tubing inlet in the lower left corner of the picture.I marked and drilled several holes in the tray that will hold the Zilla controller. Once I sort out the position of all the other electrical components, I'll be able to just mount the Zilla to it and then drop the tray in place and bolt it down.
That's all for now, back next week.
Wednesday, September 30, 2009
The Charger and a Home for the Zilla
I finished installing the charger in the electrics box in the trunk. I connected the charger to the power line that comes in from the gas door, and mounted the charger itself to the floor of the box. I also mounted the DC to DC converters in the box, simply bolting them down into place, and I sealed the perimeter of the box where it meets the chassis, to be sure that any water that splashes up can't get in the trunk area.
I still need to finish up the wiring on the for the converters and connect the charger to the batteries, but as I don't have them yet, that will have to wait. One of the things you can't see is a port in the back of the box that will vent fresh air into the compartment. When the car is running, or when the charger is on, a fan will kick on to force fresh air into the box, helping to keep everything cool. I also need secure that wire loom to the top of the box and eventually cut the carpet that was there to accommodate the opening.
I mentioned yesterday that I'll be using the original location that was used for the car's electronics as the home for the Zilla and anything else I can squeeze in there. Here's a shot of that space complete with an aluminum sheet I cut to fit.
That sheet will act as a tray that I can mount the Zilla and the hairball to. I still need to build the support for the sheet, it will sit a little higher than where it is in the photo. I'm a bit concerned I'm going to run out of room for all of the electrical doodads that I need to install. Some of them I can put under the tray because I won't need to access them unless they fail. Others I may end up running into the cabin and mount under the dashboard. I'll just have to play it by ear.
I still need to finish up the wiring on the for the converters and connect the charger to the batteries, but as I don't have them yet, that will have to wait. One of the things you can't see is a port in the back of the box that will vent fresh air into the compartment. When the car is running, or when the charger is on, a fan will kick on to force fresh air into the box, helping to keep everything cool. I also need secure that wire loom to the top of the box and eventually cut the carpet that was there to accommodate the opening.
I mentioned yesterday that I'll be using the original location that was used for the car's electronics as the home for the Zilla and anything else I can squeeze in there. Here's a shot of that space complete with an aluminum sheet I cut to fit.
That sheet will act as a tray that I can mount the Zilla and the hairball to. I still need to build the support for the sheet, it will sit a little higher than where it is in the photo. I'm a bit concerned I'm going to run out of room for all of the electrical doodads that I need to install. Some of them I can put under the tray because I won't need to access them unless they fail. Others I may end up running into the cabin and mount under the dashboard. I'll just have to play it by ear.
Thursday, August 20, 2009
Back Component Box
Pictured above is the box in the trunk with three of the cars components in it. The charger on the right, and two DC to DC converters. None of it is wired up yet, or even bolted in for that matter. This is just a dry fit test. Though you can't see it, there's a cord that runs out of the back of the box on the charger's side. That runs to the fuel door on the passenger side of the car. One of those cables you see will be routed back to connect to that. The other cable will be connected to the batteries in the box that you can barely see at the very bottom of the picture.
Also on that side is a 2" tube ducted into the box to provide fresh air to the charger when it's operating. The charger has two fans in the back that vent air out the front into what will be the interior of the trunk. I need to make sure fresh air can get to those fans, and that stale air has a way out (that vent will be elsewhere). Once I've put some paint on the steel I cut to make room for that, I'll be ready to bolt it all into place.
The DC to DC converters will be wired in parallel and will put out the 12 volts needed for the car's normal electric systems, and about 80 amps continuous, 100 amps peak.
Tuesday, August 4, 2009
More Cutting in the Trunk
Today was spent cutting out the bulk head in back of the trunk, that separated the trunk from the fuel tank area. Here's what it looked like before:
And after:
I have a bit grinding to do to get the opening nice and even, but that won't take too long. I'm going to have a plastic box built, just like the battery boxes, to fit in that space. I built another mock up out of cardboard to make sure it all fits.
This new box won't hold batteries (not enough room). Instead I'll be mounting the charger and the DC to DC converters. After giving it lots of thought, I decided to go with two DC to DC converters. Each one can put out about 40 amps at 12 Volts DC. The power steering pump alone can pull up to 75, so clearly one just wouldn't be enough.
I had thought that I'd put in an auxiliary 12 battery to handle the extra load, but realized the battery alone wouldn't be a good plan. Instead I'm going with two converters AND the battery. It just keeps getting more complicated. But that's ok, I'm trying to build this so that I have as few compromises as possible.
By the way, thanks to my good friend Len in Malta for the great suggestion of using the back of the trunk and fuel tank cavity in such a productive way. Hope you're well Len!
And after:
I have a bit grinding to do to get the opening nice and even, but that won't take too long. I'm going to have a plastic box built, just like the battery boxes, to fit in that space. I built another mock up out of cardboard to make sure it all fits.
This new box won't hold batteries (not enough room). Instead I'll be mounting the charger and the DC to DC converters. After giving it lots of thought, I decided to go with two DC to DC converters. Each one can put out about 40 amps at 12 Volts DC. The power steering pump alone can pull up to 75, so clearly one just wouldn't be enough.
I had thought that I'd put in an auxiliary 12 battery to handle the extra load, but realized the battery alone wouldn't be a good plan. Instead I'm going with two converters AND the battery. It just keeps getting more complicated. But that's ok, I'm trying to build this so that I have as few compromises as possible.
By the way, thanks to my good friend Len in Malta for the great suggestion of using the back of the trunk and fuel tank cavity in such a productive way. Hope you're well Len!
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