Showing posts with label Frame Leak. Show all posts
Showing posts with label Frame Leak. 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, 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.
Monday, March 12, 2012
A Missed Anniversary and Motor Drama
Some of you may be distantly aware that March 2nd marked the Z3's second year on the road. Unfortunately, as you know, it's not actually on the road at this time. It has once again, fallen victim to a motor problem. Of the 12 month span starting last March until now, the car has been on the road for only 6 1/2 of those months. Not all that time was to repair motor problems. Last July, August and beginning of September was spent adding the MasterFlux AC system and getting the car ready for EVCCON. Never the less, it has has not been as trouble free as I would have liked. But I remain optimistic that those types of problems may soon be behind me and I'll be in for some extended trouble free motoring.
So let's move on with what's been happening the past couple weeks. To catch everyone up to date that hasn't read the last couple posts, the car developed a leak to ground. That means that I could measure the high voltage on the frame of the car. That poses a few problems, one being the threat of being shocked, another being the threat of arcing and potential fire under the right circumstances, and last, the charger wouldn't stay on. The charger is grounded to the chassis of the car, so when it sensed the high voltage on the chassis, it simply shuts itself off for protection.
I'd methodically tracked the problem down to the motor, finding that there was a leak from the terminals where the high voltage is sent into the motor, to the case itself. This is not supposed to happen, but it can if there's been a build up of dust inside the motor caused by the wear of the brushes. Most recommend blowing out the motor out with compressed air, which I did, repeatedly. In the mean time, I contacted George Hamstra from Netgain to find out if there was a preferred method for cleaning the motor more thoroughly. Compressed air is pretty much it. He reasoned that I must have brushes in the car that are better suited for racing and tend to dust quite a bit. So he took it upon himself to send me, at his expense!, a set of $320 replacement brushes. Not just any brushes, mind you, but Helwig split top brushes, pretty much the best money can buy.
The top two brushes are tied together on one connecting wire. That is one of the older sets. Presumably, they were the same size as the new Helwig brush at the bottom, but look how much they've worn after only 9,000 miles. Notice too how the old brush closest to the new one is shorter than the top brush. Curiously, this was the case with each pair. The brush that was in the bracket closest to the front of the motor was warn by as much as 1/8th of an inch more than the back brush. I don't know if that means anything, but it certainly happened.
I've mentioned that George is tired of seeing me suffer through problems with the motor. He also offered at that time to simply replace the motor, but I asked him to hold off to see if more cleaning and the new brushes made a difference. The new brushes arrived on the 1st of March, but I didn't get a chance to work on the car until the 4th. I was able to pull 3 sets of the old brushes out with no difficulty. But on the 4th set, I was able to get one brush out OK, but the space was so tight and constrained, I simply could not get the last brush out. After laboring over it for a few hours, and coming to terms with it for another the next 24 hours, I finally came to the decision that I was going to have to pull the motor and transmission out of the car. Believe me, that was something I did NOT want to do.
My dad was kind enough to come over and help me out. It took us about 4 hours, but we got everything unhooked, the motor free and then we were able to drop it out of the car. I've lent my lift to a friend, so I didn't have that, but it's OK, because this time I was determined to drop the motor out instead of lift it out. with the cunning use of the floor jack, several 2x4s, levers and muscle power, we were able to do it. That gave me access to the last brush, and I carefully pulled it out. It was at that point that I looked at the brush I just pulled and saw something truly astounding. Take a look:
Yes, what you see there are 3 holes drilled into the top of the brush, and a chunk of the brush missing! Where it went, I have no idea. I looked around everywhere, but could not find the piece or pieces of carbon laying about. As it was the last brush I pulled, it should have come out with the brush, but it didn't. It got me wondering if perhaps it had come off and become wedged somewhere inside the motor, causing the short. It seems unlikely, but I have no way of knowing without disassembling the motor.
With the brushes out, I took the opportunity to blow more air through the motor. A lot more air. The air gun I had been using works fine, but the nozzle is fixed and short. I bought an air gun with an 8" flexible nozzle that I was able to carefully insert into the motor and spray in harder to reach areas.
I sprayed compressed air until I saw, or could smell no more dust. Believe it or not, that dust has a funny smell (even though I was wearing a mask). I put the new brushes back in carefully, and took another reading with the Ohm meter. To my astonishment, the leak was actually a bit worse. I hooked up a 12v battery to the motor with a switch in line so that I could run the motor for a bit and try blowing more air while the motor was moving. Had to be careful not to stick the nozzle anywhere in the motor or near the brush assembly. 4 or 5 more tanks of air and no dust coming out. At this point, the motor is as dust free as I can get it without taking it apart.
After all that, the leak persists. At it's worse I measured the resistance between the S1 terminal and the case at 508 Ohms. That's enough to pass 320 milliamps. Again, not a lot, but certainly enough to feel, and enough to render the charger useless.
I contacted George with the story, telling him the results of my efforts, and sending him the picture of the brush. At this point I'm faced with either taking the motor apart and trying to clean it further, or getting a new one. George was absolutely dumbfounded when he saw that picture. He said that it looked like someone had tried to make a Brush Wear Indicator, but he couldn't figure out why they drilled three holes, or worse yet, why they left that brush in the motor. He was pissed, and justifiably so. He's paid to have this motor repaired twice and the second time he told them to pay particular attention to it so that it was done to the highest standard possible. Clearly, that didn't happen.
Fed up with the whole thing, George is sending me a new motor. I must say, that I have very mixed feelings about this. On one hand, I'm thrilled to be getting a motor that will hopefully have none of the flaws that have plagued this motor from it's first day. On the other hand, it just eats me up that this whole fiasco has cost George so much. Shipping to Illinois and back, twice, two rebuilds of the motor, and finally a whole new motor plus the shipping for that from Illinois. Dreadful! I had hoped to be one George's success stories.
While all of this is going on, I am planning a couple minor enhancements. I bought a voltage meter/display from Lightobject that can be programmed to cut a relay at a specific voltage. I'm thinking that I'd like to add that to the car as a safety backup in case the charger doesn't cut off in time. If this device sees the voltage rise to the level I've defined, it would trigger a relay that would simply cut power to the charger, protecting the batteries. Stay tuned.
So let's move on with what's been happening the past couple weeks. To catch everyone up to date that hasn't read the last couple posts, the car developed a leak to ground. That means that I could measure the high voltage on the frame of the car. That poses a few problems, one being the threat of being shocked, another being the threat of arcing and potential fire under the right circumstances, and last, the charger wouldn't stay on. The charger is grounded to the chassis of the car, so when it sensed the high voltage on the chassis, it simply shuts itself off for protection.
I'd methodically tracked the problem down to the motor, finding that there was a leak from the terminals where the high voltage is sent into the motor, to the case itself. This is not supposed to happen, but it can if there's been a build up of dust inside the motor caused by the wear of the brushes. Most recommend blowing out the motor out with compressed air, which I did, repeatedly. In the mean time, I contacted George Hamstra from Netgain to find out if there was a preferred method for cleaning the motor more thoroughly. Compressed air is pretty much it. He reasoned that I must have brushes in the car that are better suited for racing and tend to dust quite a bit. So he took it upon himself to send me, at his expense!, a set of $320 replacement brushes. Not just any brushes, mind you, but Helwig split top brushes, pretty much the best money can buy.
The top two brushes are tied together on one connecting wire. That is one of the older sets. Presumably, they were the same size as the new Helwig brush at the bottom, but look how much they've worn after only 9,000 miles. Notice too how the old brush closest to the new one is shorter than the top brush. Curiously, this was the case with each pair. The brush that was in the bracket closest to the front of the motor was warn by as much as 1/8th of an inch more than the back brush. I don't know if that means anything, but it certainly happened.
I've mentioned that George is tired of seeing me suffer through problems with the motor. He also offered at that time to simply replace the motor, but I asked him to hold off to see if more cleaning and the new brushes made a difference. The new brushes arrived on the 1st of March, but I didn't get a chance to work on the car until the 4th. I was able to pull 3 sets of the old brushes out with no difficulty. But on the 4th set, I was able to get one brush out OK, but the space was so tight and constrained, I simply could not get the last brush out. After laboring over it for a few hours, and coming to terms with it for another the next 24 hours, I finally came to the decision that I was going to have to pull the motor and transmission out of the car. Believe me, that was something I did NOT want to do.
My dad was kind enough to come over and help me out. It took us about 4 hours, but we got everything unhooked, the motor free and then we were able to drop it out of the car. I've lent my lift to a friend, so I didn't have that, but it's OK, because this time I was determined to drop the motor out instead of lift it out. with the cunning use of the floor jack, several 2x4s, levers and muscle power, we were able to do it. That gave me access to the last brush, and I carefully pulled it out. It was at that point that I looked at the brush I just pulled and saw something truly astounding. Take a look:
Yes, what you see there are 3 holes drilled into the top of the brush, and a chunk of the brush missing! Where it went, I have no idea. I looked around everywhere, but could not find the piece or pieces of carbon laying about. As it was the last brush I pulled, it should have come out with the brush, but it didn't. It got me wondering if perhaps it had come off and become wedged somewhere inside the motor, causing the short. It seems unlikely, but I have no way of knowing without disassembling the motor.
With the brushes out, I took the opportunity to blow more air through the motor. A lot more air. The air gun I had been using works fine, but the nozzle is fixed and short. I bought an air gun with an 8" flexible nozzle that I was able to carefully insert into the motor and spray in harder to reach areas.
I sprayed compressed air until I saw, or could smell no more dust. Believe it or not, that dust has a funny smell (even though I was wearing a mask). I put the new brushes back in carefully, and took another reading with the Ohm meter. To my astonishment, the leak was actually a bit worse. I hooked up a 12v battery to the motor with a switch in line so that I could run the motor for a bit and try blowing more air while the motor was moving. Had to be careful not to stick the nozzle anywhere in the motor or near the brush assembly. 4 or 5 more tanks of air and no dust coming out. At this point, the motor is as dust free as I can get it without taking it apart.
After all that, the leak persists. At it's worse I measured the resistance between the S1 terminal and the case at 508 Ohms. That's enough to pass 320 milliamps. Again, not a lot, but certainly enough to feel, and enough to render the charger useless.
I contacted George with the story, telling him the results of my efforts, and sending him the picture of the brush. At this point I'm faced with either taking the motor apart and trying to clean it further, or getting a new one. George was absolutely dumbfounded when he saw that picture. He said that it looked like someone had tried to make a Brush Wear Indicator, but he couldn't figure out why they drilled three holes, or worse yet, why they left that brush in the motor. He was pissed, and justifiably so. He's paid to have this motor repaired twice and the second time he told them to pay particular attention to it so that it was done to the highest standard possible. Clearly, that didn't happen.
Fed up with the whole thing, George is sending me a new motor. I must say, that I have very mixed feelings about this. On one hand, I'm thrilled to be getting a motor that will hopefully have none of the flaws that have plagued this motor from it's first day. On the other hand, it just eats me up that this whole fiasco has cost George so much. Shipping to Illinois and back, twice, two rebuilds of the motor, and finally a whole new motor plus the shipping for that from Illinois. Dreadful! I had hoped to be one George's success stories.
While all of this is going on, I am planning a couple minor enhancements. I bought a voltage meter/display from Lightobject that can be programmed to cut a relay at a specific voltage. I'm thinking that I'd like to add that to the car as a safety backup in case the charger doesn't cut off in time. If this device sees the voltage rise to the level I've defined, it would trigger a relay that would simply cut power to the charger, protecting the batteries. Stay tuned.
Friday, February 24, 2012
Brushes and Carbon Dust
While at EVCCON 2011 I had the good fortune to catch a talk given by Tom Brunka from the Helwig Brush Company. Tom went into great detail about how brushes for DC motors work, the different properties they can posses depending on the way they are manufactured, and the care of brushes and motors. On the face of it, it seems this talk would be astoundingly boring, and in fact I think Jack Rickard scheduled it for the last talk of the conference precisely because he figured it would be lightly attended and would be in no danger of running long and interfering with the events planned for later that day. As it turned out, it was a truly fascinating talk and it went much longer than expected due to the fact that attendees started asking questions as soon as Tom finished and simply wouldn't let up. Eventually Jack had to put a halt to the exchange so that we could all go outside and race our cars. What a great time that was.
One of the things that Tom mentioned is that brushes will wear and break in at one rate, but once they are bedded in, they will wear at a completely different rate. The wear of the break-in rate is much higher than standard wear rate. But the interesting thing is, if you disturb the brushes, i.e. remove and replace them, lift them out of their holder, nudge them, breath on them, or even look at them askance, they will begin to wear at the break-in rate again. This level of wear has a couple of effects. First and perhaps most obvious, your brushes wear out faster. As a direct result of that faster wear rate you encounter the second issue, which is an accumulation of the dust that wore off the brushes on the inside of the motor. If you have the motor ventilated with forced air, some of that dust will be carried out of the motor's vents. But not all of it.
Such is what has happened with my motor. Faithful readers will remember that I have had the motor out of the car a couple of times due to a strange phenomenon where the balancing putty fell off the armature. On both occasions George Hamstra at Netgain motors, shipped the motor back to Warfield electric and had them repair it. In order to do so, they had to dis-assemble it. Now I didn't look at the brushes when the motor came home from the first repair so I don't know if new brushes were installed, but I did look at them the second time and they were the same brushes that were in the motor when it left. How do I know? Well new brushes are not contoured to fit perfectly against the armature when they are new. As I said earlier, they must be worn, or bedded in and this can take up to 5000 miles to do. But since the brushes had necessarily been removed during the motor's repair, that meant they were going to go through another instance of excessive wear and re-bedding; meaning more dust.
What does this have to do with my current situation? Well, all that carbon dust is conductive. After all, it's through that very carbon that the current is pushed to the armature of the motor. I have a fan on the motor, pushing 110 CFM of air through it and likely carrying out a good percentage of the carbon dust along with the heat it's meant to blow out. But clearly not all the dust is going out. Somewhere within the motor, some dust has piled up and allowed a small path for current to flow from the high voltage fields to the case. That's not good but apparently not unheard of. Normally, you simply blow the motor out with compressed air and the problem leaves the motor in a plume of black dust.
So, I charged up my compressor, took the shroud for the fan off the front of the motor and started blowing. There was plenty of dust. More than I expected. I thought this was great, it meant I likely fixed the problem. Unfortunately not. The problem is that in order to get all the necessary components in the car for it to function, Or simply because I'm very bad at designing things, all the components are crammed in there so tight it's difficult for me to get a nozzle in there to blow out every nook and cranny. But my blow gun's nozzle is right at the end of the trigger limiting where I can really point it.
I've exchanged some emails with George and he suspects that the brushes in the motor right now are a high performance brush called H49 which do great for racing, but tend to dust a lot. He thinks that the H60 brushes, which are a harder, street grade brush would be better suited for my build with the added benefit that they will produce less dust. He's decided to send me a set of these at no expense. Well, no expense to me. They normally run over $300 a set and George is picking up the bill. To say that George is fed up with my motor is an understatement. He's stated that he will not RMA the motor again. Meaning, if it ever has another problem, he intends to replace it. Believe me when I say that it's very comforting knowing that he will stand behind the motor so resolutely. For now, I just don't see a reason to do that, and here's why.
The new brushes will arrive early next week. I've ordered a blow gun for my compressor with a 12" flexible hose which will allow me to better squirt air in all the nooks and crannies inside the motor. I'll remove the old brushes, and push 8 or 10 tanks of air through the motor, then replace the brushes. If all goes well, I should see the short go away. Depending on the temperature, and consequently the time of day, the resistance of that short fluctuates between 1.18K Ohms, and .85K Ohms. That means a potential leak of current in the range of 135 to 188 milliamps. If I can't resolve the short and I have to take the motor out of the car then I'll have to decide whether I want to try to disassemble it to clean it, or simply give George the go-ahead to send out a replacement. I really don't want to do that though.
One of the things that Tom mentioned is that brushes will wear and break in at one rate, but once they are bedded in, they will wear at a completely different rate. The wear of the break-in rate is much higher than standard wear rate. But the interesting thing is, if you disturb the brushes, i.e. remove and replace them, lift them out of their holder, nudge them, breath on them, or even look at them askance, they will begin to wear at the break-in rate again. This level of wear has a couple of effects. First and perhaps most obvious, your brushes wear out faster. As a direct result of that faster wear rate you encounter the second issue, which is an accumulation of the dust that wore off the brushes on the inside of the motor. If you have the motor ventilated with forced air, some of that dust will be carried out of the motor's vents. But not all of it.
Such is what has happened with my motor. Faithful readers will remember that I have had the motor out of the car a couple of times due to a strange phenomenon where the balancing putty fell off the armature. On both occasions George Hamstra at Netgain motors, shipped the motor back to Warfield electric and had them repair it. In order to do so, they had to dis-assemble it. Now I didn't look at the brushes when the motor came home from the first repair so I don't know if new brushes were installed, but I did look at them the second time and they were the same brushes that were in the motor when it left. How do I know? Well new brushes are not contoured to fit perfectly against the armature when they are new. As I said earlier, they must be worn, or bedded in and this can take up to 5000 miles to do. But since the brushes had necessarily been removed during the motor's repair, that meant they were going to go through another instance of excessive wear and re-bedding; meaning more dust.
What does this have to do with my current situation? Well, all that carbon dust is conductive. After all, it's through that very carbon that the current is pushed to the armature of the motor. I have a fan on the motor, pushing 110 CFM of air through it and likely carrying out a good percentage of the carbon dust along with the heat it's meant to blow out. But clearly not all the dust is going out. Somewhere within the motor, some dust has piled up and allowed a small path for current to flow from the high voltage fields to the case. That's not good but apparently not unheard of. Normally, you simply blow the motor out with compressed air and the problem leaves the motor in a plume of black dust.
So, I charged up my compressor, took the shroud for the fan off the front of the motor and started blowing. There was plenty of dust. More than I expected. I thought this was great, it meant I likely fixed the problem. Unfortunately not. The problem is that in order to get all the necessary components in the car for it to function, Or simply because I'm very bad at designing things, all the components are crammed in there so tight it's difficult for me to get a nozzle in there to blow out every nook and cranny. But my blow gun's nozzle is right at the end of the trigger limiting where I can really point it.
I've exchanged some emails with George and he suspects that the brushes in the motor right now are a high performance brush called H49 which do great for racing, but tend to dust a lot. He thinks that the H60 brushes, which are a harder, street grade brush would be better suited for my build with the added benefit that they will produce less dust. He's decided to send me a set of these at no expense. Well, no expense to me. They normally run over $300 a set and George is picking up the bill. To say that George is fed up with my motor is an understatement. He's stated that he will not RMA the motor again. Meaning, if it ever has another problem, he intends to replace it. Believe me when I say that it's very comforting knowing that he will stand behind the motor so resolutely. For now, I just don't see a reason to do that, and here's why.
The new brushes will arrive early next week. I've ordered a blow gun for my compressor with a 12" flexible hose which will allow me to better squirt air in all the nooks and crannies inside the motor. I'll remove the old brushes, and push 8 or 10 tanks of air through the motor, then replace the brushes. If all goes well, I should see the short go away. Depending on the temperature, and consequently the time of day, the resistance of that short fluctuates between 1.18K Ohms, and .85K Ohms. That means a potential leak of current in the range of 135 to 188 milliamps. If I can't resolve the short and I have to take the motor out of the car then I'll have to decide whether I want to try to disassemble it to clean it, or simply give George the go-ahead to send out a replacement. I really don't want to do that though.
Friday, February 10, 2012
Battling a Frame Leak
This is a god-awful long, and most likely boring story. Once again I'm hoping I can serve as an example to all you fine readers, for what not to do.
About two weeks ago I pulled the Z3 into the garage and plugged it in. When I flipped on the charger I heard, what sounded like, a popping noise coming from the front of the car. It sounded like the noise you hear when you plug a speakers into the audio port on your computer, deep and quick. But there were some kids playing out front and I wasn't sure exactly where the noise came from. But the charger continued to charge and everything on the car checked out.
The following day I went to plug it in after another day's driving and I listened closely, this time with the garage door closed and the hood up. Sure enough, I heard the same pop, only this time the charger turned itself off. You may remember about a year and half ago, I was measuring one of the batteries during a charging cycle when one of the probes slipped and made contact with the chassis and the terminal at the same time. There was a pop, the end of my probe was vaporized, the charger shut off and the breaker for the 240 volt AC outlet tripped. That little mistake cost me $150 because I had to send the charger back to Manzanita to repair the AC rectifier which I blew up in the process.
After this recent pop I figured 1. I must have a high voltage leak to ground and 2. I'm going to have to send my charger along with another $150 to Manzanita. I decided to check for the leak and got out my multimeter. Sure enough, if I measured at the most positive terminal on the battery pack, and the chassis, I could measure the full 160 volts of the pack. Damn! I went to the fourth battery from the end of the pack and measured there and got the expected 13.2 volts. I wondered how much current could get through this leak, so I clipped a regular automotive tail light bulb to the positive terminal of that battery and the chassis and it glowed nice and bright. If there were no leak, or no path for current, that bulb would not light up.
OK, it was time to start disconnecting things to isolate where the leak was. This should be a pretty straight forward task, and it seemed to be at first, but it wasn't long before it got weird. I'll explain. I started by unhooking all the peripherals, one by one, using the multimeter after each to see if I had voltage to ground. I disconnected the DC to DC converter, the charger, the Masterflux A/C system, the ceramic heating element and finally the Link-Pro meter. By this time only thing hooked to the high voltage system where the Zilla controller, the motor and the batteries them selves, but still the leak was present. I unhooked the cables leading from the Zilla to the motor and the leak was gone. Ah ha, found it!
My guess was that through poor design, I'd placed a cable close to something sharp and it had rubbed through and shorted to the chassis. In deed, I found what looked like a suspicious wear mark on top of one of the rubber boots, under which is one of the terminals of the motor. But as it happened, it had not worn through, though it would have eventually. But then I noticed that I'd done something else that was remarkably stupid. The main high voltage fuse of the car, which is held in a special holder which does not keep the fuse from sort of sliding one direction or another, had migrated one direction and looked like it was touching a part of the chassis. Well, there you go!!!
I fixed that problem and insulated the connection so that it can creep all it wants and will never short against anything again. I checked all the other cables and connections and found them good, so I started putting everything together. I got everything back together, put the multimeter on the car and... I could still read the pack voltage. Ah crap! But this time, there was an important difference. When I performed the light bulb test, there was not enough current flowing through the chassis to make the bulb light up. At this point, I'm thinking there must have been two leaks. I'm assuming I fixed the more serious one, but there's still a smaller one.
Now's where things get strange. I started testing again, trying to be as methodical as possible, but I kept getting strange results, or results I didn't expect and couldn't explain. For a while I was certain there was a leak through the Zilla, but that wasn't the case. You see the problem is that I've run up to the end of my knowledge at this point. When it comes to electrical stuff and electronics, if I can't SEE it, I'm probably not going to understand it. I can SEE a wire touching the frame. But once that wire enters a device, as far as I'm concerned what goes on in there is simply magic.
I'll save you some of the wretched details, but suffice it to say after disconnecting everything one at a time, again, I was left with only the batteries connected to the Zilla and I still had a leak. But then I saw that I still had the current sensing leads from the Link-Pro connected to the shunt. I thought well that can't be the problem, but I'll disconnect them to be sure. Lo and behold, the leak went away. What the hell!! Maybe that line got pinched or abraded. Nope, it looked fine. The meter is supposed to be completely isolated from the chassis because I've used an isolating DC to DC converter specifically to power the meter. I measured the 12 V output of that DC to DC converter and found that I could read 12 Volts if I grounded to the chassis. Well that's not supposed to happen! There's my problem!! Or so I thought.
I started putting everything back together, one thing at a time, taking measurements with each connection made. For kicks I connected the Link-Pro's shunt lines, expecting to see the leak and it wasn't there. Ah, for crying out loud! In fact, I measured the output of the Link-Pro's DC to DC converter power supply and it now no longer has any connection to ground. Still scratching my head, wondering what the hell is going on, I connect the motor back up and the leak reappears. Right about now, I'm prepared to burn the car to the ground and walk away.
Ignoring the Link-Pro issues for now, I focus on the motor. I took the Zilla out of the loop and had simply a small pack of 12 cells and the motor ready for testing. I hooked the negative line from the battery to the negative input of the motor, which happens to be labeled 'A1'. Then I put the multimeter on the positive end of the battery and the car's chassis and I could read the battery's voltage. That means there is a path for current from the battery, through the motor, into the chassis and back to the battery. I measured the resistance and found that it was 1.19K ohms. Now that's not much, and if I plug that into an Ohm's law calculator taking into account the full 160V pack voltage, that means that leak can pass only 0.135 amps, or 135 milliamps.
I don't think that's normal. I believe that the high voltage fields are supposed to be completely isolated from the case of the motor, but I could be wrong. I know that leak hasn't existed in the past. Truth is, I have no idea what might cause that, but I have emails in to some experts who hopefully will help me with that.
The good news through all this is that at one point I had the battery pack isolated from everything else and was able to connect just the charger to it. I crossed my fingers and threw the switch. It came on, stayed on and was charging the batteries perfectly. No need for repairs there.
As for the Link-Pro and it's DC to DC converter, I have no idea why it would pass through the high voltage at one point and not another. I'm wondering if that little converter has capacitors that were storing the power. I really have no idea. Again, as far as I'm concerned, that thing is magic. But I did order a replacement DC to DC converter for a whopping $8.50 that I'll keep handy in case I need to swap out the other one.
If you made it though this and are still awake, congratulations! If you have any words of wisdom you'd like to share or guidance to offer, I'm keen to hear it. Just leave it in the comments.
About two weeks ago I pulled the Z3 into the garage and plugged it in. When I flipped on the charger I heard, what sounded like, a popping noise coming from the front of the car. It sounded like the noise you hear when you plug a speakers into the audio port on your computer, deep and quick. But there were some kids playing out front and I wasn't sure exactly where the noise came from. But the charger continued to charge and everything on the car checked out.
The following day I went to plug it in after another day's driving and I listened closely, this time with the garage door closed and the hood up. Sure enough, I heard the same pop, only this time the charger turned itself off. You may remember about a year and half ago, I was measuring one of the batteries during a charging cycle when one of the probes slipped and made contact with the chassis and the terminal at the same time. There was a pop, the end of my probe was vaporized, the charger shut off and the breaker for the 240 volt AC outlet tripped. That little mistake cost me $150 because I had to send the charger back to Manzanita to repair the AC rectifier which I blew up in the process.
After this recent pop I figured 1. I must have a high voltage leak to ground and 2. I'm going to have to send my charger along with another $150 to Manzanita. I decided to check for the leak and got out my multimeter. Sure enough, if I measured at the most positive terminal on the battery pack, and the chassis, I could measure the full 160 volts of the pack. Damn! I went to the fourth battery from the end of the pack and measured there and got the expected 13.2 volts. I wondered how much current could get through this leak, so I clipped a regular automotive tail light bulb to the positive terminal of that battery and the chassis and it glowed nice and bright. If there were no leak, or no path for current, that bulb would not light up.
OK, it was time to start disconnecting things to isolate where the leak was. This should be a pretty straight forward task, and it seemed to be at first, but it wasn't long before it got weird. I'll explain. I started by unhooking all the peripherals, one by one, using the multimeter after each to see if I had voltage to ground. I disconnected the DC to DC converter, the charger, the Masterflux A/C system, the ceramic heating element and finally the Link-Pro meter. By this time only thing hooked to the high voltage system where the Zilla controller, the motor and the batteries them selves, but still the leak was present. I unhooked the cables leading from the Zilla to the motor and the leak was gone. Ah ha, found it!
My guess was that through poor design, I'd placed a cable close to something sharp and it had rubbed through and shorted to the chassis. In deed, I found what looked like a suspicious wear mark on top of one of the rubber boots, under which is one of the terminals of the motor. But as it happened, it had not worn through, though it would have eventually. But then I noticed that I'd done something else that was remarkably stupid. The main high voltage fuse of the car, which is held in a special holder which does not keep the fuse from sort of sliding one direction or another, had migrated one direction and looked like it was touching a part of the chassis. Well, there you go!!!
I fixed that problem and insulated the connection so that it can creep all it wants and will never short against anything again. I checked all the other cables and connections and found them good, so I started putting everything together. I got everything back together, put the multimeter on the car and... I could still read the pack voltage. Ah crap! But this time, there was an important difference. When I performed the light bulb test, there was not enough current flowing through the chassis to make the bulb light up. At this point, I'm thinking there must have been two leaks. I'm assuming I fixed the more serious one, but there's still a smaller one.
Now's where things get strange. I started testing again, trying to be as methodical as possible, but I kept getting strange results, or results I didn't expect and couldn't explain. For a while I was certain there was a leak through the Zilla, but that wasn't the case. You see the problem is that I've run up to the end of my knowledge at this point. When it comes to electrical stuff and electronics, if I can't SEE it, I'm probably not going to understand it. I can SEE a wire touching the frame. But once that wire enters a device, as far as I'm concerned what goes on in there is simply magic.
I'll save you some of the wretched details, but suffice it to say after disconnecting everything one at a time, again, I was left with only the batteries connected to the Zilla and I still had a leak. But then I saw that I still had the current sensing leads from the Link-Pro connected to the shunt. I thought well that can't be the problem, but I'll disconnect them to be sure. Lo and behold, the leak went away. What the hell!! Maybe that line got pinched or abraded. Nope, it looked fine. The meter is supposed to be completely isolated from the chassis because I've used an isolating DC to DC converter specifically to power the meter. I measured the 12 V output of that DC to DC converter and found that I could read 12 Volts if I grounded to the chassis. Well that's not supposed to happen! There's my problem!! Or so I thought.
I started putting everything back together, one thing at a time, taking measurements with each connection made. For kicks I connected the Link-Pro's shunt lines, expecting to see the leak and it wasn't there. Ah, for crying out loud! In fact, I measured the output of the Link-Pro's DC to DC converter power supply and it now no longer has any connection to ground. Still scratching my head, wondering what the hell is going on, I connect the motor back up and the leak reappears. Right about now, I'm prepared to burn the car to the ground and walk away.
Ignoring the Link-Pro issues for now, I focus on the motor. I took the Zilla out of the loop and had simply a small pack of 12 cells and the motor ready for testing. I hooked the negative line from the battery to the negative input of the motor, which happens to be labeled 'A1'. Then I put the multimeter on the positive end of the battery and the car's chassis and I could read the battery's voltage. That means there is a path for current from the battery, through the motor, into the chassis and back to the battery. I measured the resistance and found that it was 1.19K ohms. Now that's not much, and if I plug that into an Ohm's law calculator taking into account the full 160V pack voltage, that means that leak can pass only 0.135 amps, or 135 milliamps.
I don't think that's normal. I believe that the high voltage fields are supposed to be completely isolated from the case of the motor, but I could be wrong. I know that leak hasn't existed in the past. Truth is, I have no idea what might cause that, but I have emails in to some experts who hopefully will help me with that.
The good news through all this is that at one point I had the battery pack isolated from everything else and was able to connect just the charger to it. I crossed my fingers and threw the switch. It came on, stayed on and was charging the batteries perfectly. No need for repairs there.
As for the Link-Pro and it's DC to DC converter, I have no idea why it would pass through the high voltage at one point and not another. I'm wondering if that little converter has capacitors that were storing the power. I really have no idea. Again, as far as I'm concerned, that thing is magic. But I did order a replacement DC to DC converter for a whopping $8.50 that I'll keep handy in case I need to swap out the other one.
If you made it though this and are still awake, congratulations! If you have any words of wisdom you'd like to share or guidance to offer, I'm keen to hear it. Just leave it in the comments.
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