A Long Overdue Upgrade

From the moment the Z3 hit the ground after I finished the conversion I knew that I was going to have to upgrade the suspension. The car's front springs were already tired, and before I added 485 lbs worth of batteries and equipment, the car was already riding 3/4 of an inch lower than stock.  After it gained all that weight, it was riding an additional 3/4" too low.  So now, both the front and the back were 1.5" too low.

I tried to reduce that 1.5" drop by adding some rubber bushings in between the lower coils of the springs.  That brought the ride height up by 3/4".  It was still a bit low, but the car looked good.  The problem was that the trouble was deeper than just ride height. The springs were never meant to carry the additional weight I'd added to the car.  When I went over a speed bump at just the right speed, the front end of the car would dip too much as I was coming down, and the car would bottom out.  The springs were simply too squishy.

So, knowing all of this, why did it take me so long to finally address this problem?  When people asked, I'd blame it on the cost of the components: all the suspension components add up to $1,500 or so.  But truthfully, it was fear.  I've never worked on any aspect of suspension systems before and as far as I was concerned the car's suspension is made up of springs, swing arms and shock absorbers all held together with  black magic and voodoo.  It seems silly really, after all, I did take a perfectly good car apart and turn it into an EV.  What could be so difficult about suspension?  Clearly this was not a rational fear.

Doing research into the subject, I came across a recommendation for a company called TC Kline Racing that specializes in BMW and Porsche suspension systems.  I contacted them and told them what I'd done, explaining that my goal was to get the car back to a normal ride height with properly rated springs.  I'd kind of anticipated this before I'd started the conversion, so I'd had each corner weighed both before and after the conversion.  That allowed me to tell them exactly how much weight each corner gained.  They informed me that the original springs were 325# rated springs, and I would need to upgrade to their 400# springs.  Those heavier springs would get me the ride height I wanted and the suspension would have the proper firmness.  The end result would be the ride should have the right feel and handle better.

The full kit included the 400# springs for both the front and back, Koni coil over struts for the front, shocks for the back and a threaded barrel and collar system that would allow me to adjust the ride height on the back of the car.  One of the claims they made was that the system weighed less than stock, which would reduce the car's unsprung weight and further improve handling.  So when everything arrived, I weighed it and it came in at 41 lbs.

My dad agreed to come over and help me with the project, which I had hoped would take only a day to complete.  <shakes head> Oh... silly boy.  I'll spare you the brutal details, but it took us about 2 hours to get the first strut done.  Getting it off the car wasn't too bad, but we needed to compress the spring so that we could get the top plate off since it needed to be re-used.  That top plate is what holds the strut assembly to the tower.  Compressing the spring was scary.  We had the right tool, but we felt like we were working with a live hand grenade that could go off at any minute.

The second strut went a bit quicker, and after 3.5 hours of work we had both new struts on the car with everything torqued down to spec.  We weren't going to set the car on the ground until I had the back end complete, so I didn't know whether the ride height had been improved or not.  So we moved our attention to the back end.

Getting the old springs off was equally as terrifying, but we got it done and took the old shocks off.  When I went to put them on, it was clear that the larger central shaft of the new shock would not fit through the stock bushing/mount.  A quick call to TC Kline and he said "You needed to order the proper new ones as the old stock ones won't fit."  You don't say!  Since I'd ordered exactly the parts they'd told me to he took responsibility for leaving them out of the package and had them rush shipped to me.  That meant a two day hiatus waiting for the parts.

When the parts arrived, I got the new shocks on the car and the new springs.  I set the car on the ground drove it down the street and back so that it would settle to it's final ride height.  I had to make a few adjustments in the back to get the right height, but the barrel/collar system made it easy to do.  I ended up setting the front struts so as to push the car up as high as the adjustment would go, and it was still 1/2" lower than stock.  I was a bit concerned, thinking that Kline's recommendations had been off.  But thinking back, the real problem was not the ride height, it was the fact that the springs were too soft.  So I decided to take the car out for a spin and put them to the test.

I was astounded at how perfect the car handled.  The car handled speed bumps perfectly, no bottoming out, and if felt like I'd remembered it did when I first bought the car.  Actually no, it felt better.  I really put it through it's paces taking a few corners near the house at speed and found that it handled better than it ever had.  There's a particular corner nearby that has a nasty bump right at the apex.  Previously when I hit that, the front would squirm a bit and the back end would kick out resulting in a relatively unpleasant feeling.  But this time through, the car took the bump like it was nothing at all.  I was so surprised an after market system could be that much better than the stock BMW suspension.  But to be fair, the stock system was 13 years old and had 149,000 miles on it.

I weighed all the parts that came off the car and they totaled 50 lbs.  A savings of 9 lbs, some of which is considered unsprung weight.  TC explained to me that a spring's weight is considered half sprung and half unsprung.  Makes sense.  Incidentally, I spoke with TC personally on the phone 2 or 3 times.  He was very personable and helpful and he took the time to educate me.

I guess the lesson learned here is that if you're converting a car, don't wait to have the suspension addressed to handle the new weight.  If I'm fortunate enough to convert another car, I'll be incorporating that cost into the initial build cost estimates.

When it was all said and done, the car rides 1/2" lower than stock, and looks great.  But more importantly, the springs are rated correctly for the new weight of the car.  Why did I wait so long?

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.

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.

EVCCON 2012, Charging, and a Watchdog

There's no denying it, this is a long over due update.  Since I last wrote about the charger blowing up, there have been a few events worth noting, and a change in the charging system worth mentioning.  Let's get to it.

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.

Fred Behning and his MGTD

Jeff Greeson's 914.  Take away that blue cord and it's looks like a show piece.

John Allen's Celica.  A beautiful job in every respect.

Kevin Heath and his RX8.  He has every reason to be proud of this build.

Jason Horack's Daytona.  Well laid out, neat and tidy.

Dale Friedhoff's Ranger.  It won best wiring/layout award.

It's inevitable that a fair number of people are going to look at any conversion.  The better they look, the more professional they appear, the more likely people are to take them seriously and not view them as a science project, or worse a rolling death trap that is bound to electrocute someone.  I personally think that producing fine cars like this pushes the cause of EVs forward a bit faster.

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.

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.  

Notice the neat glowing switch on top of the box.

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.  

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.

A Look at the Bottom

Juvenile jokes aside, at the end of the last post I alluded to the fact that I was interested in seeing how the batteries were doing since I bottom balanced them in February of 2011.  Quite a lot has happened with the car since then.  The batteries have been through 353 cycles.  They've put out 2209 kWhs of electricity and then had it stuffed back in.  I've driven a total of 6324 miles.  The car has been out of commission twice for motor problems, and off the road for a grand total of 7 months.  During those occasions, the battery pack was partially disassembled with half of the cells out and laying on the floor of my garage, while the other half remained connected together in the car.   That last point has concerned me a bit.  I've wondered all along if having them apart might have introduced some variable that may have caused cell drift.  I kind of doubt it, but I simply wasn't sure.  So, I set out to find out. 

Last Sunday I had a chance to drive down to the brand new Tesla store in Scottsdale and take a first hand look at the Model S.  I even passed someone that was out for a test drive in one of the demo cars.  I don't believe I've seen a bigger grin on someone's face while they were driving.  It was a great trip, but I'll write about that later.  At any rate, with a round trip to Scottsdale, and a couple errands thrown in, I'd used about 95 amp/hours out of the pack's 120 amp/hours available.  I decided to make a quick trip out to run the batteries down a bit more.  I figured I'd get up to 115 amp/hours or so and then run the rest down by running the heater in the car.

I set off for a quick 10 mile lap that would do it, when I had a second thought.  I remembered that the last time I'd charged the batteries, the charge had cut off a bit early with the top cell being about 3.40 volts.  That equates to the pack starting off about 7 to 10 amp/hours down, so I decided to cut my trip short.  Turns out that was a good thing.

As I was driving adjacent to my neighborhood heading for a specific entrance, I noticed the car was not really accelerating any more.  A half mile before that I'd accelerated to 40 mph with no problem but now, it was acting dead.  I turned into the neighborhood quickly and headed for home nursing the car the whole way.  I'd brought my multi-meter along but I was afraid if I stopped, I wouldn't get going, so I coasted (running a couple stop signs along the way) and turned the final corner to my house.  As I was heading up to the garage, I was hoping the door made it open in time because if I had to stop, there was no way I was going to get it up the hill of my driveway into my garage.   I made it in, but the car was dead.  It would barely move the 6 more inches I wanted to go.  I quickly jumped out and measured the cell I know to have the lowest capacity and it was at 2.043 volts.  I started measuring others and they were in the 2.5 to 2.7 volt neighborhood.  Well, that doesn't seem balanced to me!  I decided to let the batteries rest for an hour or so and come back to measure them.

By the way, when I pulled into the garage, I'd used 113 amp/hours (for those of you keeping score at home.)

Now, I'll elaborate on this more in a moment, but take note.  The lowest cell was 2.043 volts right after it had had a load on it, which is just above what CALB considers dead.  The car would barely move.  Yet no cell was below 2.0 volts and no cell was ruined.

I came back an hour later and measured the cells and found that the gaps, or differences I'd seen in the voltages had closed up dramatically.  The lowest cell that was 2.043 volts had bounced back and was now 2.684 volts; the highest cell was 2.937 volts.   I should let the numbers speak for themselves.

You can see that the cells were mostly between the 2.700 and 2.800 range, with a few just 1/100 off in either direction.  But there were 4 that were more than 5/100's of a volt off, with the spread from the lowest to the highest cell at 0.253 volts.  Three things come to mind looking at this data.  First, they aren't balanced.  Second, the amount by which the are out of balance is quite small.  At that end of the discharge curve, the difference between 2.684 volts and 2.937 volts is a fraction of an amp hour.  The third thing is that I think I simply wasn't patient enough when I performed the bottom balance.  You may have heard this elsewhere, or experienced it yourself if you've ever bottom balanced a pack of batteries, but it is an extremely boring, tedious, and lengthy endeavor.  Or to put it another way, it sucks big time.

On that first attempt at bottom balancing, it wasn't until after I was sick of the whole process and charged the batteries back up that I realized the proper thing to do would have been to let them rest for several hours to be sure they remained balanced.  I had them all within 1/200ths of a volt when I charged them, but I now know that if I'd waited, I would have seen them settle, and found they were likely a bit further off.  I think that inaccuracy is reflected in the variations in this data. 

In spite of my ineptness demonstrated here, I must have balanced them well enough to be, what I consider, successful.  The car would not have moved another 10 feet if I needed it to, yet no cell went below 2.00 volts let alone reversed itself and died a horrible death.  Something a top balanced pack simply can't do.

Now, I know what you're thinking.  "But Tim, you brought on this situation yourself.  This was completely and utterly self inflicted!  There was no need what-so-ever to discharge the pack this much.  I never intend to take my pack that low and expose them to this peril.  Consequently I'll never face the jagged, rocky bottom of the discharge curve, risking one or any cells in the process."   In part, you're right.   But consider this.  These cells, like any other, lose capacity over time.  How much and how fast is determined by how you treat them.  The problem is, the dangerous, jagged bottom of the curve sneaks up with every charge.  In other words, a pack that started out as a 120 amp/hour pack eventually becomes a 110 amp/hour pack, and then 100 amp/hour pack.  If you don't know where the bottom is, you risk hitting it and running a cell or 10 into reversal.  Since mine are bottom balanced, I "see" that imbalance at the top.  The charger cuts off at a preset voltage and the batteries will eventually reach that voltage regardless of how many amp hours they can actually hold.  The difference is, if I hit bottom the car stops moving and the batteries are fine.

So what's a fella to do at this point?  Best try to balance them again and do it properly.  This was monumentally difficult.  Not because the job is hard, and not because the batteries put up a fight or anything.  Rather because it's miserably hot and humid in AZ at the moment and spending 3 days in the garage balancing the batteries was not my idea of a good time.  One of those days was 18 hours long!  Suffice it to say, I got them all between 2.757 and 2.761, 4/1000ths of a volt, and that was with letting them rest for 4 hours at the end, before I put the charger on them.

One of the key pieces of information I wanted to get and was eager to share with you was the total number of amp/hours that went back into the pack.  That really is a measure of how the batteries have held up to the 545 cycles they've seen.  Sadly because of another, yet different stupid mistake, I'm not able to share that with you.  In may haste to get the pack balanced and the car back on the road, and my zeal to get it done right, I forgot something very important.  When ever you disconnect the main battery pack from an e-xpert pro meter, you MUST remove power from the meter.  I forgot to do this.  I opened the car and saw the following...

Notice the haze in the lower corners of the display?  The sharp eyed ones among you may also notice that the meter is not actually displaying any data.  I opened the door and immediately smelled the distinct aroma of a fried circuit board.  NOOOOOOOOOOO!   It gets better.  I took it out this morning, hoping to send it back to Evolve Electrics for repair, and this is what I discovered:

I'm no doctor, but that does not look good.  This meter was a few oxygen atoms away from catching fire.  I'm not sure if the deformation of the cylinder is clear in the photo, but it is not healthy looking.  Don't be like Tim.  Disconnect power from your meter before you work on the battery pack.  Incidentally, it fried the 1:10 prescaler as well.  *Sigh*

So, the end result of that is that I don't have a precise number to give you regarding how much power the batteries were able to accept when I finally charged them.   I can tell you that I turned the charger's dial to what I believe to be the position where it delivers 20 amps, and it took almost exactly 6 hours to charge.  That works out to 120 amp/hours, but it's really no better than a guess at this point. 

10,000 Electric Miles

I pulled into the garage last night and noted the amp/hours I'd used and the mileage on the odometer so that I could record them like I do every time I charge the car.  The mileage read 144,214 which is significant because that marks exactly 10,000 miles since the Z3 was reborn as an EV.  I figured that this would be a good time to go over some of the numbers I've been collecting that last 2 years, 4 months and see what I could glean, and then share them with you. 

530        Number of Charge Cycles

18.9       Mean average miles driven between each charge
34.9%    Mean average depth of discharge
36.0%    Median average depth of discharge (half the data points are above, half below 36.0)


WARNING: Wild numbers and speculation will now commence. 

CALB says that these batteries are good for 2000 cycles at an 80% Depth of Discharge (DOD), and 3000 at 70%.  But how long will they last if I'm averaging roughly 35% DOD?  Of course no one knows.  However, if you use the 50% increase we see going from 80% DOD to 70% DOD as a baseline, and extrapolate that out, we might be able to conclude that we could get 4500 cycles at 60% DOD.  If we keep going and then apply it to my average DOD of ~35%, we come up with something close to 12,500 cycles.  At 18.9 miles per cycle, that works out to 236,250 miles. 

Of course that's all theoretical, but it's likely not too far off from reality.  But let's be conservative and say I only get half that number of cycles out of the batteries, that's still 118,000 miles.  However, we need to keep in mind that the original 2000 and 3000 cycles that CALB states is a bit misleading.  It's not as if the batteries stop working when they get to 2000 cycles.  What they really mean is that after 2000 cycles to 80% DOD, the battery will only hold 80% of it's original capacity, so they will still push the car as far as I need to drive on a daily basis.

</Wild numbers and speculation>

As you can see this whole "cycle life" or "life expectancy" question for the batteries is highly fluid with the real numbers determined by a number of factors all at once which are, for practical purposes, impossible to determine or track.  One thing that is certain is that these batteries will out perform a lead acid pack by at least an order of magnitude.  Seeing as they only cost 4 times as much as a lead acid pack, I call that a good bargain.  And that's not even taking into account the numerous other benefits they offer, like the 60 mile range vs. a lead acid packs 20 miles (at best). 

$1,402    Amount saved not buying gas
3639       Total number of kWhs used to charge the car

That $1,402 figure is derived by taking into account the price of gas when I charged the car and subtracting the cost of the electricity used to charge the car.  I always charge the car at off peak hours, and I add an extra 10% to the amount of electricity consumed to take into account the inefficiencies of the charger as it converts the 240 Volts AC to 160 Volts DC. 

So how has the car performed?  How well has it used that energy?

376        Mean average Watt-hours consumed per mile
388        Mean avg Watt-hours/mile with the old solid brushes
319        Mean avg Watt-hours/mile with the new split brushes

You can see there's been a marked difference in efficiency since replacing the brushes.  The old average of 388 Watt-hours per mile was experienced over 442 charge cycles and 8,184 miles.  The average has dropped to 319, and that has been over 88 charge cycles and 1,816 miles.  I don't know how one could dispute the claim that these Helwig Carbon split Red Top brushes are better. 

That increase in efficiency has moved the car from a 50 mile range using the 388 Watt-hours per mile figure to 61 miles using 319 Watt-hours per mile.  Of course most of you know how much range can fluctuate with an EV depending on how and where you drive.  I've been on 40 mile trips with the car where I saw the energy consumption average drop to 266 Watt-hours per mile, which works out to 73 mile range.  Is that useful data?  I don't know, but it's interesting.

Expanding on that, I found 4 data points that fit together nicely.   These are individual trips with the miles driven, the total kWhs used and the Watt-hours used per mile.

50 miles      17.23 kWhs    345 Watt-hours/mile
51 miles      17.89 kWhs    351 Watt-hours/mile
51 miles      16.49 kWhs    323 Watt-hours/mile
51 miles      14.57 kWhs    286 Watt-hours/mile

Guess which trip occurred after the new brushes were installed in the motor.  By the way, those were all trips to the same destination and back.

The real question at this point is how are the batteries fairing?  For those not familiar with the car and reluctant to go back and read the multitude of tedious posts, I bottom balanced the pack back in February of 2011.  The only way to find out how the batteries are doing now is to draw the pack back down to the bottom and make note of the amp/hours taken out and the state of charge on each battery.  Hmm... sounds like another post.  Stay tuned.