Zach’s Electric Diablo

My seat is now bolted to the floor and the racing harness is installed.

I also installed the Mac mini, 12v power supply and an LCD screen (the LCD mount is temporary until I mount the dash). This setup will be helpful during testing to display battery status and speed information.

Now that I am starting to accumulate the 12v devices, I thought it was about time to officially wire up the DC to DC converter. It takes the pack voltage and charges the 12v lead acid accessory battery.

My Dad came into town for a few days and Saturday morning was our time to work on the car. He helped me install the repaired axle and the new spacers I made. Everything fit perfectly. Then we took it down to Big-O to get it aligned. After about an hour of working on it, the guy got it “mostly” aligned. Apparently, my rear a-arms don’t have the proper geometry to get it 100% aligned properly. I’ll go into more details about this later.

When we got back to the shop we took it out for a spin. I don’t have a speedometer yet, but we must have got it up to 50-60mph in and around the parking lot. It felt REALLY good. It accelerated very quickly and handled quite nicely (though, I don’t have seatbelts and my batteries are not 100% strapped in so I didn’t push it too hard). I’ll get some video on Monday.

I will be installing my re-assembled axle tomorrow and I wanted a little insurance to make sure it doesn’t come apart again.  So, I cut out a 1/2″ spacer to go between the axle and the transmission:

I also welded up an aluminum battery box for the auxiliary battery:

It still needs to be painted.

While waiting for my axle to come back, I decided to spend some time cleaning up the wiring. I replaced the short pieces of 2-0 wire with some custom copper jumpers (like the ones that came with the batteries.) for the short connection from the fuse to the shunt and from the shunt to the relay.

I also machined some aluminum offset connectors so that the cables can easily exit the battery box.

I wired up my Iota 55 DC-DC for the first time. It spit out 13.6v just like it’s supposed to.

I also spent some time making a short term to-do list:

1. Re-install the axle and do a proper test-drive (with video documenation)
2. Build harness for auxiliary 12v battery.
3. Buy and install seatbelts/harnesses
   (a coworker showed me his 6-point racing harness. Very cool. Very expensive.)
4. Bolt down the driver’s seat
5. Build the 12v relay panel
6. Install Mac Mini and power supply
   (mainly this is designing a mount for the Mini)
7. Start dashboard layout
8. Revise the BMS design
9. Design safety cover for the high voltage electronics
10. Install the heater/AC unit
11. Figure out motor-to-AC compressor system.
12. Weld the firewall closed
    (there is a big hole where the fuel cell was supposed to be mounter)
13. Weld / reinforce the the center console area.
    (I cut out a big portion of the center console to make it thinner. It was wide where the fuel cell sat)
14. Mount the body on the chassis (this is mainly building the mounting points for the roll cage)

I’m sending the axle back to the guy that made them.  His name is Frank and he runs http://driveshaftshop.com/

He is going to inspect the axle for damage and reassemble it.  He has given me great customer service and I would definately buy axles from him again.

With my batteries charged, I took it out for its first real test drive. I pulled out of the garage and headed for the parking lot. I gave it a little throttle and it took off quite nicely. I made the first turn and suddenly all the power disappeared. This coincided with the start of a grinding sound emanating from one of the rear tires. After rolling to a stop, I got out to see what happened. My CV joint had come apart at the hub. After a short forklift ride back to the shop, I pull the drive shaft to assess the damage:

It looks like it just pulled apart. I think it is easily re-assembled. However, I’m not sure WHY it came apart in the first place. I’ll need to do some postmortem sleuthing to figure it out.

I disabled comments this morning because I became inundated with spam.  If you want to contact me, just hit the link in the upper right hand corner of this page.

After replacing 50 resistors and finding out that RJ-45 connectors can fail in a very unfortunate way (the terminals inside the socket get bent and short out with their neighbor), all my battery monitors came online. This was exciting, but it was also the point that I looked back and thought about all the things I would like to change. Version 2.0 of the BMS may not be that far off…

In addition to that, I started soldering up the main power system controller. This board will talk to the battery monitors, read the current shunt, and handle all the general data collect for the vehicle. It will report all this info to the MacMini via USB. I haven’t populated it completely yet, but it is complete enough to replace my previous interface to the BMS:

One of my co-workers commented on this setup saying “Why is it that electronics guys always have the jankyest setup for communications?” My reply was, “I needed something quick, and it worked… for a little while”.

Here is the new setup. USB plug on the left and connectors to the BMS boards in the center.

For those interested in building their own BMS, check out http://batteryvehiclesociety.org.uk/forums/viewtopic.php?t=1245

Peter is doing a great job documenting his design process (much better than I have) and the overall design looks quite good. I even stole borrowed a few ideas for my controller.

After spending some time with the battery pack and BMS it appeared that I might have three (out of the 40) bad boards.  The weird thing was that all three were failing in the same way.  I took the boards back to the bench, plugged them in to my bench supply and they worked.  After a bunch of messing around I realized I could make them fail if I adjusted the supply lower than 3v.  Hey wait a minute, I thought I already fixed this problem.   Turns out I have a bug in my “fix”.  I had added a transistor and resistor to bump up the voltage on the LED side of the opto-isolator.  However, I chose too high a value for the current limiting resistor.  I didn’t do the math when I originally tested the “fix”.  I just tried a resistor I had laying on the bench and it worked.  However, it really shouldn’t have.  Now I need to take all the BMS boards off and replace that one resistor on each.  What a pain!