Bad SLI battery

Well, on my way to work Wednesday morning the check engine light came on solid. This is the Zilla’s way of telling me that something is amiss. The can continued to drive with full power and the Zilla wasn’t overheating (according to the gauge) so I continued my drive. Once in the parking garage I plugged in my laptop and looked at the error codes. I was surprised to see a whole bunch of 'em:

1224 - SLI battery too low and caused shutdown of controller
1221 - Major Overspeed Either Motor Beyond redline by X
1223 - SLI battery below warning threshold
1124 - Main Contactor Stuck On

2 of these, the overspeed and contactor stuck on are pretty serious, but the motor wasn’t over-reved, and the contactor was not stuck on…

By the way, SLI stands for Starter, Lights, Ignition since that's the role the battery plays in a gas car. In an EV, it's more of a buffer to keep the 12v system running during heavy loads.

I cleared the errors and thought I’d take a look at it again on the way home.

After work I drive the car out of the garage without the check engine light lit. On my way home the light came on steady again. It was raining so I was using my wipers and headlights, so then I started to think the real error was low SLI battery voltage and this low voltage was causing the Zilla problems in its logic which made it think the motor was over revving or the contactor was stuck.

A few blocks from my house it did stall, but I was able to get it running again and brought her home.

I tested the voltage on the SLI battery – 12.4v, not too good. I got out my 12v charger and charged it up.

The next day I drove it to work when the check engine light came on again. Once in the garage I checked the error codes and this time it was just 1223 - SLI battery below warning threshold. I left work a little earlier to avoid using the headlights, and it wasn’t raining, so the trip home was, other than the check engine light staying lit, uneventful.

Back at the house the SLI battery again showed 12.4v. I put it on the charger for a couple of hours, but when I removed the charger the voltage started to drop. In an hour it was back at 12.4v - must be a bad battery.

I checked on line and the nearest auto parts store, Kragen, doesn’t carry them. I tried Sears, and they don’t carry them either. I was thinking I was going to have to order one on line and pay a hefty shipping fee, when I found that Auto Zone did carry them and the one 20 minutes away had one in stock!

Saturday I pulled the old battery, picked up the new one and gave them the old one in return. Connected it up and thought I was all set…

Monday on the way home the light comes on again! Same error, 1223. I put the new battery on the charger and checked under the hood to see if my Iota was disconnected. It was wired fine, but I did find one of its fuses blown. Not sure when this would have happened (maybe when installing the new battery?), but this must be why the new battery died on me. Just the same, the old battery was bad because it wouldn't hold a charge.

So, moral of the story?
- Low SLI battery will make your Zilla think strange thoughts
- Check your fuses!