PHEV conversion using CAN-View and BMS+

Oh, I had a thought about why i had two unexplained battery overheat episodes: I think that 6 parallel packs is inherently unstable. I might be off on my understanding of the physics involved but having hundreds of individual cells having to be in near perfect balance seems unstable.

With three packs, a setup where I never had a battery overheat or explode, I think that any given cell running a little out of balance, i.e. a little under-volted, will have a small amount of energy "poured" into it from the other cells. But as you add more packs, there is more and more energy available that can be poured down the hole of a bad cell.

Considering that with six packs, I actually had a pack catch on fire, I believe that there is just too much energy being held back. And I had cooling fans running!!! My last plan had been to isolate at least some of the packs with contactors or maybe have them come online at different times with contactors. I never got around to it but I'm wondering if anyone knows about the effects of increasing parallelism.

I know that these batteries are prone to runaway heating but it seemed much harder to control with 6 packs. One or more packs would often go from ambient to extremely hot several hours later, even with cooling fans. And I never charged over 235 volts. In fact, more typically, within a few minutes of disconnecting charger (which I never left on) the voltage would have dropped to 232-235.

Interestingly, even after one pack caught on fire and one pack accordioned out, the other four packs were cool to the touch. Very weird chemistry.

 

If I recall correctly, it is just plastic clips after the screws are removed. I think there were a couple of those standard white plastic doohikies that hold half the car together. Just give a firmer tug and cross your fingers.

 

I found the source of the red triangles. High voltage cable had rubbed a bare spot and was shorting to the body of the car.