Alright, so I have no idea what happened to my pack. It's a massive LiFePo4 8S23P battery, charged by a solar charger, and discharged by a 3000W inverter. I have several theories, one of which is a prime candidate, but I don't know how to test for it. They are:
1. The pack was over-charged. The BMS was correctly cutting off the charge at 30v, (24v) battery, so this seems unlikely, but if it wasn't balanced, possible
2. The pack was over-discharged. Again, the BMS does correctly cut power - but again, badly unbalanced, it's a possibility.
3. The BMS was continually bleeding cell row 1, causing it to run flat, while the other 7 rows were fine. This is my favourite.
4. Single possible single cell short, causing the destruction of every other cell in that group?
5. Something else?
Here's a photo of the pack:
The cells look like this:
The rest of the pack looks like this:
The facts from testing are:
1. The puffed cells are at 30% capacity, and terrible internal resistance.
2. The non-puffed cells have 100% original capacity. I can't load test such a large pack for internal resistance.
3. The gaffer's tape holding every other string together have pulled off, showing that at one point they too puffed, but deflated back. This doesn't fit with my favourite theory.
I'm fairly certain I'll never find out for sure what happened, but I'm keen to know what you think might have happened.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 on 36S
eCar: Mitsubishi Outlander PHEV... Waiting for warranty to expire
eHouse: Still on grid, but with LTO batteries and 3kw LF inverter...
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