ejetta

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.

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.

Now that my car has been running for a while, I’ve been looking into ways to increase my range. It currently stands right around 15 miles.

I had been running my motor at 108V, 600 amps maximum. All things being equal, getting more power from voltage rather than amps should keep the motor cooler and also let it run at higher RPMs. This should result in higher efficiency (more electrical power converted into mechanical power).

When I had my arcing trouble, one thing I looked into was the brush advance. This motor, which is an FB1-4001, can have the brushes advanced for “clockwise” or “counter-clockwise” rotation. It can also be set to neutral. The neutral setting is for forklifts or vehicles that want to go equally fast forwards and backwards (and don’t use a reverse gear to do this).

I thought my brushes were advanced correctly, but I considered the problem again to make sure my old assumptions were correct. I put the car in first and lifted the car so that one wheel was just barely off the ground. My wife spun the wheel forward while I watched the commutator inside the motor. I marked the rotation direction on the motor case.

To advance the timing, the brush holder end of the case should be rotated as far as it can go opposite the direction that the commutator rotates. You can see here that there’s 2 exposed holes where the case could be mounted. So, my brushes are actually retarded.

One other thing that was confusing to me was the terminology. If you look at the brush holder end of the motor, my commutator rotates clockwise. However, the motor documentation calls this counter-clockwise rotation. The motor documentation considers that the drive shaft end of the motor is the clock face.

Here’s a picture of the holes and how they are marked in the motor documentation.

My typical morning commute is 14.3 miles. This is from Balboa Ave / 805 to my Son’s preschool in Sorrento Valley and then back up to University City. I have made this drive reliably twice. My motor voltage / amp settings were 120V/400amps both times. The hardest part is I-805 from Sorrento Valley Rd. to La Jolla Village Dr. My pack bottoms out at 136V going up this and my speed bottoms out at about 45 mph. My controller is set to not let the pack go below 136V.

I tried a more ambitious drive on Sunday from Clairemont to Ocean Beach. The total loop was 21.2 miles and I had a 1.5 hour opportunity charge in OB. I went Balboa to 163 to 8 into OB and then Sea World Drive to 5 to Balboa coming home. I did alright until I got to Balboa on the way home. My pack couldn’t maintain 136V going up that hill. I ended up shifting down to first gear and going up the hill at 15 mph. That’s a little over 15 miles into the trip.

So, for now I’m saying that my range is an honest 15 miles. Maybe if I charge up in University City and drive up and down Miramar Rd. a couple times I can go farther, but that’s not real driving in San Diego.

My LinkPRO reads about 20 amp hours when my pack starts bottoming out, and that seems consistent with the 100amp discharge curve for the Fullriver DC100-12 battery.

One of the things I’m really hoping to do well is capture data from all the systems on my car. I have started by logging data from the Soliton Jr. controller. This is an example of what I can get from the controller.

20110420_96v600a

I have to take the controller data, which is sampled at 100 Hz and downsample it to 1Hz to work with it in a spreadsheet if I want to look at a whole 15 minute drive.

I have a LinkPRO, a PakTrakr and an old Delorme Earthmate GPS. When I put the data from all of these together I should be able to do some really interesting stuff. For example, I should be able to use the PakTrakr data to identify any weak batteries by looking at which ones voltage drops the lowest under load. I should be able to use the GPS to come up with 0-60 times and quantify the effects of hilly terrain on my top speed and range.

I have been driving around for the last few days with my motor current limit set to 400 amps and the motor voltage limit set to 120 volts. This keeps me out of arcing for the most part, except when I hold the accelerator all the way down for more than a couple seconds. If I heard arcing, I would let up on the accelerator a little and then ease it back down.

This is no way to drive around. I really need to be able to stomp on the pedal and know that everything is going to be OK. I did some more drive testing and settled on a value of 108 volts as keeping me out of arcing no matter what I do to the pedal.

The funny thing is that I don’t really notice any practical difference in performance between 108 or 120 volts. I can get up to 30mph in first gear and 45 in second. Third takes me up to about 60 and I can get to 70 in fourth. This is pretty much in line with my expectations. I probably had been backing off on the throttle before I could get to 120 volts.

Now that I have water cooling installed on my controller, I increased my current limit up to 600 amps (the maximum). The early results look like it’s hard to maintain 600 amps for more than about 1.5 seconds before the controller goes into thermal cutback. The cutback goes down to just over 500 amps. This still needs more testing.

I ordered my springs today from www.coilsprings.com. I decided the front ride height is OK, just the back needs to be raised. They already had the pattern for the factory springs, so I didn’t have to send them a sample. This is good because my car doesn’t have factory springs on it. The factory spring part number is 1H5511115J. I should have my new springs in 4-6 weeks.

With the car at my house, I felt comfortable doing some more testing. My first priority was eliminating the arcing. Fortunately, the car makes a very distinctive sound when this happens. It always happens when the car is near the top of the RPM range in first or second gear.

Here’s how it looks under the car:

I would drive in first gear as fast as I could until I heard the arcing (about 20mph). Then, I pulled over and reduced the controller output voltage. I started with an output voltage of 144. I reduced it to 120, 108 and finally to 96. At 96 volts, I couldn’t get the arcing to happen in first or second, so I’m going to leave it at this setting for now.

The next priority is getting the performance up to the point where I can drive on major streets. I found that when I first pulled out of my driveway, I could pull 120-130 battery amps. After a couple blocks, it was down to 80 or 90. After a rest, it would go back up to a little over 100. I don’t have data logging set up yet, but I’m assuming this behavior is a result of the controller going into thermal derating. I don’t have any liquid cooling at all connected to the Soliton Jr. I ordered up the biggest PC water-cooling pump and radiator I could find.

Also, while driving the controller shut down 3 times. When this happens, the car coasts. Pulling over and cycling the ignition switch gets it started up again. There were log messages that indicated the 12V supply was too low. I have a charger for my 12V battery on order. I suspect that the 12V battery was pulling too much current and dropping the output voltage of my DC/DC converter. Hopefully getting a good charge into the battery will take care of it.

I drove the E-Jetta home successfully. There’s not a lot to report. The car is just barely drivable in its current state. My top speed was about 40mph on the flats. Going up the big hill (Linda Vista Rd) I could barely go 25mph. I didn’t measure my state of charge or amps because I hadn’t hooked up the shunt yet.

I noticed some arcing from the motor as the RPMs went up near the tops of first and second gears. I had to be very careful to keep the RPM low. I had the Soliton Jr’s output set to 150 volts and 600 amps.

My wife followed me so that I would have some help if the need arose. Fortunately, there were no other problems. The whole drive took about 35 minutes.

This is the route I took. My main consideration was going up the gentlest grade climbing out of Mission Valley.

View Larger Map

This is how the back end looks with all 9 batteries in the trunk. It’s probably drivable, but I think it will scrape on my driveway. It turns out that this car has aftermarket springs and shocks in the back, so that is probably not helping either.