braincore
100 mW
Having seen/read about li-ion packs combusting, I'm interested in hearing what can go wrong.
First off, the pack to be built is 20S-7P (72V, 35Ah) of 21700 5mAh cells (supposedly panasonic 2170A). The pack will use a BMS (JK BMS) to balance, protect over-charge/discharge, limit current, etc. It doesn't look like these cells have a PTC built-in, but being new to all of this, I could be mistaken.
I've read about lithium dendrites forming which can cause an internal short. The worst case will be an internal short causing a 7P pack to short and triggering thermal runaway. I assume this is extremely rare for high-quality batteries that aren't overcharged or fast-charged, which will be the case with the BMS configuration. Nevertheless, assuming I have a microcontroller fully recording the BMS's measurements of each 7P pack, what are the signs that dendrites are forming to dangerous levels? Can it be fully inferred by a drop in capacity?
Are there any other catastrophic failure modes I need to plan for? Are certain types of physical punctures more catastrophic than others?
First off, the pack to be built is 20S-7P (72V, 35Ah) of 21700 5mAh cells (supposedly panasonic 2170A). The pack will use a BMS (JK BMS) to balance, protect over-charge/discharge, limit current, etc. It doesn't look like these cells have a PTC built-in, but being new to all of this, I could be mistaken.
I've read about lithium dendrites forming which can cause an internal short. The worst case will be an internal short causing a 7P pack to short and triggering thermal runaway. I assume this is extremely rare for high-quality batteries that aren't overcharged or fast-charged, which will be the case with the BMS configuration. Nevertheless, assuming I have a microcontroller fully recording the BMS's measurements of each 7P pack, what are the signs that dendrites are forming to dangerous levels? Can it be fully inferred by a drop in capacity?
Are there any other catastrophic failure modes I need to plan for? Are certain types of physical punctures more catastrophic than others?
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