Bottom Balance 2012

I finally got around to doing another bottom balance. The goal was to confirm my instrumentation readings and to verify that the batteries had stayed balanced over the course of 11 months and almost 11,000 miles of driving.

First, I drove until my LinkPro indicated almost 180 amp hours. I did reset my trip odometer after charging, so I was able to drive 72 miles on a single charge.

Then I used my CBA-III to discharge each battery using a constant 30 amp load:

The results:

I charged the pack back up using my Zivan NG5:

Here’s the first time I charged the pack last year for comparison:

I found out a few things that I want to remember for next time. First, the CBA-III shut down due to overheating several times (which is why I don’t have numbers for the first 10 batteries on the plot). I solved this issue by pointing a powerful fan at the CBA-III and that took care of the issue.

Another point is that I use really long leads to discharge the batteries. Last time, I had found that the CBA-III was measuring about 2 volts when the battery was down to about 2.5 volts. This time, I found I had to go down to 1.5 volts. I must have messed up last time and not really taken as many amp hours out of the batteries as I meant to. The voltages shown in the plots are as measured by the CBA-III. I did not actually take my batteries down to 1.5 volts!

The batteries had between 1300 and 2200 minutes of run time remaining. This translates to between 10 and 18 amp hours. I take this to mean that I didn’t quite hit the bottom last time I balanced. Also the LinkPro might be reading a little more consumption than actually occurred.

There’s one battery in particular (#41) that didn’t fall in the same range as the others. I’m not sure if it’s failing or if it was just that far out of balance with the others. It definitely needs more investigation.

The charger seems to be working great. If I integrate the amps delivered into the pack over time, I end up with about 175 amp hours. The charger is supposed to be set up to be conservative, with a cutoff voltage of just over 180 (about 3.6 V per cell).

Posted in Uncategorized | Comments Off

Weight

I don’t know why I put off weighing my car for so long. I went to Ace Relocation on Eastgate Dr. The Jetta weighed in at 3260 lbs. The factory weight is listed at about 2900 lbs. So, 360lbs increase for an Electric conversion. Not too bad, it’s like having 2 180lb passengers in the car all the time.

The next thing to do is figure out the tire pressure. My car has Falken ZE-512 tires. The size is 205/50 R15. Each tire can carry 1168 lbs at 51 psi. Let’s say the Jetta weighs about 3500 with some passengers in it. That’s 875lbs per tire. So, 875/1168 * 51 = 38.2. So, I should have 38.2 psi in each tire, assuming the weight is distributed easily. Unfortunately the scale can only weigh the whole car, so I don’t have separate numbers for each axle.

Posted in Uncategorized | Comments Off

Update 4/30/2012

I don’t have a lot of news to report (which is good). My conversion first hit the road a little over a year ago. Since then, I’ve put just over 6,000 miles on it. About 2,600 of that was on the AGM batteries and the remaining 3,400 is on the new LiFePo4 setup.

I’m getting some more suspension work done, hopefully later this week. The front springs are actually mismatched! The passenger side is a lowering spring and the driver side is an OEM style spring. Also, the driver side front wheel bearing is on its way out, so that is getting replaced.

I’m really starting to want a cleaner interior, especially the headliner. I’m going to start shopping for an upholstery shop to do that.

I also need to do a range test and bottom balance. Not for any technical reason; I just want to see how the batteries are holding up . My expectation is that they would all have similar amp-hour capacities remaining after driving the car as far as I dare. Maybe having a tow truck standing by would be a good idea. Doing laps around my neighborhood would get boring fast.

Also, I still haven’t established my range. I think just over 60 miles is still the farthest I’ve driven.

I’m still keeping this page up to date, especially the mileage count (odometer reading): EV Album

Posted in Uncategorized | Comments Off

Lithium Upgrade

Everything had been working pretty well. I was driving my car 4 days a week and charging at work. I had put 2600 miles on the Jetta this way. Of course, charging at work was not ideal. A couple people showed up with Nissan Leafs and wanted to “share” my plug. It was hard to get the word out that I _needed_ the spot by the cooling plant or else I couldn’t go home. Then the weather started to get “cold”. This is San Diego, so “cold” means it was getting under 40 degrees Fahrenheit at night. One morning in mid October, I ran out of power about 2 miles from work. The Jetta was able to creep in to the office in “limp home” mode, but I realized I was asking it to do more than it could do. The Fullriver AGM batteries were just not adequate.

I parked the Jetta at home and went back to driving my gas car. I started planning my upgrade to LiFePo4 batteries. I have been following Jack Rickard and a lot of the threads on diyelectriccar.com. There are also a couple Kick Gas Club members who have LiFePo4 batteries. I had heard a lot of good things about CALB batteries. Their distributor, Calib Power, is located pretty close by in Pomona. I did some calculations and figured I could fit 56 of the 180 AH cells in the space that my 15 Fullriver DC100-12 batteries were occupying.

The only question was the vertical clearance under the hood. I built a wooden model of the CALB SE180AHA cell and tried it in a few positions to see how far forward it could be without interfering with the hood. Based on this, I decided to eliminate 2 rows of cells up front (6 cells). This took my total down to 50 cells, for a 160V nominal pack. It seemed reasonable to reduce the cell count rather than completely rebuild my front battery box.

For charging, I purchased a Zivan NG5 used back in the fall of 2010. I hadn’t used it with the AGM batteries because I wanted to experiment with using Minn Kota chargers to charge each AGM battery separately. I sent the Zivan NG5 off to Elcon in Sacramento for reprogramming for my 50 cell, 180 AH lithium pack.

I worked with Keegan at Calib power to get my batteries. Everything went very smoothly. I paid him a check about a week in advance so it would have a chance to clear. Then I drove to Pomona to pick them up. The batteries were new in their sealed crates with manuals and manufacturers testing reports. They come 14 to a crate, so there was one partial crate with 8 batteries in it. I also bought the CALB copper interconnects and terminal hardware.

Batteries new in crate

The next step was mounting the batteries. In the front, I built a frame from 3/4″ square steel tubing and 3/8″ threaded rod. This compresses the batteries together and then holds them down on the existing platform. I used Industrial Metal Supply in Kearny Mesa for my metal needs. They are great. I especially like that I could order my pieces cut to length over the Internet and then go pick them up at will call.

The rear box dimensions I had originally designed with lithium batteries in mind. So, the batteries dropped right it. I just had to add some high density foam packing material around them to take up the extra space so they wouldn’t rattle around back there.

Dry fit the batteries in the rear box

I bought a lot of battery covers from VTE outlet in Michigan. They seem to have the best prices on them and I feel better having all the terminals individually covered. I also bought some terminal posts from VTE for my small gauge wiring.

For balancing, I decided to forgo a battery management system. I used a CBA III battery analyzer to drain a couple batteries. I found they were in the ballpark of 80 ah. I charged the ones I drained back up to about 80 ah (using a bench supply and a christmas light timer!) and then drove the car about 30 miles. After that, I took the CBA III and connected it to each battery. I used a USB isolator from Phidgets to keep the CBA III from blowing out the USB port on my computer. I drained each battery at 30 amps down to 2V (as shown in the CBA software). This sounds kind of low, but I was using a really long 10 gauge cable to connect to the batteries. The batteries themselves did not go below 2.5V. The CBA III kept track of the amp hours it took out of each battery. The batteries all had between 13 and 30 ah remaining in them. So, for 180ah batteries, they came from the factory pretty well balanced.

Bottom balancing new batteries

I have a PakTrakr system with 3 remotes from before. I was planning on monitoring my batteries in sets of 3. Then I realized that the PakTrakr draws 9mA from the primary battery on each remote. Over the course of a year, this would draw almost 80 ah extra from the primary batteries, leaving them significantly out of balance. My plan is to put a switch on the most negative leads of the PakTrakr remotes so I can switch them on when I need them. There’s really no need to monitor all the batteries 24/7.

I did run into one unexpected issue when connecting the batteries. CALB only offered one size of terminal interconnect, so I mistakenly thought it would work for connecting batteries in either direction (across the short end or across the long end). It turns out that connecting batteries where the long sides match up is considered a “standard” connection. Connecting across the short ends requires a slightly longer interconnect. I ended up buying copper 3/4″ x 1/8″ bus bar from Industrial Metal. I got some help from a friend at work (thanks Son!) drilling them all out with the holes in the right places.

Terminal Interconnect Spacing

Now I’m driving my Jetta again. My range was just under 15 miles with the AGM batteries on a nice summer day. My maximum range with the LiFePo4 is still untested, but I’ve driven it over 40 miles a couple times. There’s a lot of great things about the upgrade. The old battery weight was 1050 lbs. The new battery weight is 600 lbs. Handling is vastly improved. Also, the new batteries are compressed together so they don’t rattle anywhere near as much. Not having to charge at work is awesome. The only downside is the upfront cost ($1.20/ah, which comes out to about $10,800 for my set). Still, anyone building from scratch should really consider using LiFePo4. After you spend all that time on a project like this, you will really want to end up with a car you can use every day without any hassles.

Posted in Uncategorized | Leave a comment

Plotting GPS vs. Amps

I’ve been playing around with ways to look at all the data I’m getting from the¬†different¬†systems on the Jetta. Here’s one I like. The radius of the circles is amps and the color represents speed. Bigger circles = more amps. Green = higher speed. The biggest red circle happens when the Soliton Jr starts up (the controller sends one sample that’s over 2000 amps, probably a glitch).

Here’s another way to look at the same data. Speed is not represented in this plot. Red = highest amps.

Here’s the data file for the above plots. The data file is produced by my logging software. The data comes from the Soliton Jr, the PakTrakr, and a NMEA GPS receiver.

data.csv

The logging program is written in C and is pretty rough right now. I’m planning on releasing it under the GPL at some point.

This is the gnuplot script that generates the two plots shown above.

gps.gnuplot

The gnuplot commands produce svg files. I use ImageMagick “convert” to convert the .svg files to .png. I like working with .svg files a lot, but they’re not quite common enough to post on the web yet.

Posted in Uncategorized | Leave a comment

New Brushes

I got my new brushes from Helwig Carbon today. These are replacements for the originals in my 9″ ADC FB1-4001 motor. Since I ran my motor with the brushes retarded for so long, I decided to replace them. The guys at Helwig were really helpful. These brushes are custom made to match the original dimensions. Here’s the specs for my brushes.

Description:  H60
Size:  .625 X .966 X 1.25 Style:  2QP3
Grade:  H60

The new brushes are split style with the Red Top pad and 4 leads.

I’ll be putting them in this weekend. At this point the Jetta isn’t limited by motor performance (it’s limited by battery performance for sure), so I doubt new brushes will make much difference.

Here’s some of the old brushes for reference:

Posted in Uncategorized | Leave a comment

Battery Data

My battery pack is made up of Fullriver DC100-12 and HC100-12 batteries. The HC series is really not the best for this application, but I got a good deal. Having a mix of batteries means monitoring them is really important. When one battery goes out before the others, it consumes power instead of producing it. This puts a significant extra load on the rest of the batteries.

Here’s an example of how I look at my battery data. The voltage comes from a PakTrakr. The mileage is derived from GPS. The plots are made with gnuplot.

Here’s a good battery on a recent drive. This is a brand new Fullriver HC100-12.

Here’s a bad battery on the same drive. It’s a Fullriver DC100-12. I’ll be replacing it soon.


Here’s another battery that’s old but still in good shape (it’s also a DC100-12):

 

Posted in Uncategorized | Leave a comment

GPS Data

This chart shows motor current and GPS data. Green is less current and red is more. The trip starts at Rosecrans and goes to Balboa. This was created by plotting my log data with gnuplot.

Posted in Uncategorized | Leave a comment

LinkPRO Amps

I’m using a Xantrex LinkPRO as my only EV-specific instrumentation. I have a interface box that a friend built. The interface box scales the pack voltage down and also isolates the RS-232 output from the LinkPRO. I have a Deltec 50mA/500amp shunt in series with my pack for measuring current. The shunt connects directly to the LinkPRO (it doesn’t go through the interface box).

I had been getting really bogus numbers for my amps readings. Like, never over 100 amps. I could tell from the log data from the Soliton Jr. that I was hitting the pack current limit (set to 250 amps).

This puzzled me for a long time. I tried using different kinds of twisted pair cable and shielded cable to connect the shunt to the LinkPRO. I tried all the settings in the LinkPRO that looked relevant. I tried telling the LinkPRO that I really had a 900 amp shunt.

Finally, I tried changing the mode on my Soliton Jr. from “Performance” to “Quiet”. Performance mode switches at 8 kHz. Quiet mode switches at 14 kHz. This seems to have fixed the problem. I see current readings from 0 up to my set limit of 250 amps.

My best guess is the the LinkPRO sampling frequency is related to the Performance mode frequency (8 kHz). Either it’s the same, a multiple of it, or evenly divides it. Another possibility is that the pack switching was interfering with the shunt signal.

Posted in Uncategorized | Leave a comment

Motor Rotation Follow-Up

I was successful in advancing the brushes on my ADC FB1-4001 Motor. I started with this drawing:

I cut out the image of the tail end of the motor. I overlayed an approximation of my existing mounts on the image. Then, I rotated the image 20 degrees and drew an approximate image of the plate I would need.

In the above image, the existing mount is blue and the new plate is red. One weekend I cut out the plate and painted it. The plate is 1/8″ steel. I cut it with a Sawsall with a metal cutting blade. I drilled the holes with my cordless drill and a lot of oil.

The next weekend, I put it in place on the car. I had to take out all the batteries so I could get at the top and at the bottom of the motor. I supported the motor with a floor jack and unbolted the mounts. I loosened up the 4 bolts that hold the end housing to the motor. I disconnected my A2/S2 jumper. I was able to easily rotate the end housing until the bolts lined up with the alternate set of holes. Then I tightened the housing bolts into the new holes.

After that, I put my new plate in. All the holes lined up! I bolted the plate to the motor and I bolted the existing mounts to the plate. I had to hold nuts between the mount bolts and the plate to attach the existing mounts.

Now, I’m driving with my voltage limit set up to 150V. Performace is a lot better. I don’t notice a huge difference in range. I’m planning on replacing my brushes with new ones from Helwig Carbon since some of the existing ones were a little crumbly.

Posted in Uncategorized | Leave a comment