I think the following:
some sealants/glue/whatever are not working 100% as intended, maybe it’s just a batch or maybe it’s for every car out there, when water/moisture penetrates those sealants some kind of shorts are produced, causing errors on the bms system and slowly increasing the temperature of the cells, when that temperature reaches a critical point due to many consecutive shorts/errors battery catches fire
BMW engineers must have reproduced the way this can occur and calculated the rate at wich that temperature can increase so knowing that they just need to cool at least the same amount of temperature on a given time. They must have thought of a way to cool the battery pack using the stored energy in the battery , using the battery cooling system I suppose.
if the battery is heating at a rate of XCº per hour/minute we just need to cool down that same amount or more.
They must have considered all the other things that can heat the battery like driving aggressively etc.
It’s like when you heat the car by driving aggressive and the car prevents you from using power from the motor, because battery needs to cool down before, it happened to me several times and the bms cooled the battery “quite fast”, so they are doing the same non stop until battery reaches a safe point 30% or less.
What I don’t really know is why they state, to 30% or less, maybe when battery is on low charge safe mode or something like that something changes on any condition and the overheating problem is not going to occur anymore.
if that’s the case I only see them replacing those that really fail, even many others can be defective and or give problems or not in the future. Maybe if time passes and the majority resist without problems during the 8 year warranty…… maybe if they fail after that they don’t have to pay for the repair, but I’m not sure about that.
does all this make sense?
Sorry for my poor english, Im from Spain