openinverter forum

I'm using Gen1 Volt batteries for my project and ran into an issue today that I have not seen/realized before, hoping that anyone else running these has seen it.

I'm seeing voltage between the battery terminals and the rods running through the pack. When I first put the meter on it I have 30V, that drops quickly to about 15, then slowly and settles between 8V and 13V. This is true of every module in the car and some new ones on the bench.

I have disassembled and reassembled the pack using 1/4-20 threaded rod so that they would better fit my car. I don't think that caused the issue but I'm unsure.

Anyone else see something similar? If so any ideas on how to address? I got a minor shock when working on the main power cables today and I'd like to avoid that moving forward, and just generally fix the issue.

UPDATE: At the suggestion of some fellow NEDRA members, I measured the voltage again with a 10K resistor. That brought the voltage down to 2V +/- 0.5, which indicates a very low current.

I'm still not sure the cause. Best guess is coolant got between the plates and is conducting from the pouches to the frame, but only a tiny amount. That's just a guess. Some others are seeing the same issue, some are not.

I have seen Opel Ampera throw a dreaded "Service HV system" message and wouldnt let go. We traced the problem to isolation. However after measuring conductivity everything was fine. Its just the car decided that on charge HV to PE resistance dropped so much that it tripped.
Poor guy replaced a battery pack, charger, inverter and i lent him my HPCM2 module just in case. We then disconnected heater, AC compressor and some other aux components which are in the loop. In the end we didnt find the problem, we just disconnected PE from the charging cable and car started to charge! Not very safe... I wonder if that was bad isolation circuit in a car.

Running into this problem on some Gen 2 battery packs (some from a chevy spark and some from a volt but I believe are built of the exact same cells.) I agree with your coolant observation as when I uncompress the kleet mounting brackets the voltage from the battery in reference to the frame decreases. Interesting.

Same here with my Nissan pack. Not sure if it happens in the modules or the BMS. You get a slight tickle when touching HV and chassis. With resistor it collapses as well so I decided it's fine

johu wrote: ↑Thu Apr 07, 2022 6:13 am Same here with my Nissan pack. Not sure if it happens in the modules or the BMS. You get a slight tickle when touching HV and chassis. With resistor it collapses as well so I decided it's fine

Do you use any standard AC water heaters on your DC link? Could be the wire in them started to conduct just a little towards the casing...

arber333 wrote: ↑Thu Apr 07, 2022 6:20 am Do you use any standard AC water heaters on your DC link? Could be the wire in them started to conduct just a little towards the casing...

I do, but the small tickle was already present when I mounted the battery, not having it connected to anything.

I'm buying a megohmn meter for insulation testing now. It's good to hear that I'm not the only one seeing these voltages. I know it's a tiny amount of leakage current but I don't like the idea that it's present.