The BMS Was Supposed to Protect my Batteries?

[Davidasailor26]

Except that's NOT what Maine Sail describes in the first few sentences of his YouTube.
He says "...over 100 volts into a 12V LP battery..."

Yep, definitely 100V from a failed MPPT into a 12V battery, or paralleled group of them, would be bad news. My question is more about the middle of the video (starting around 11:30) where he talks about 4 series batteries charging at 3.65V per cell, totaling to 58.4V, which is concerningly close to the 60V. My thought is each 12V battery’s BMS is still only exposed to the normal 14.6 volts, not the threatening 60V the whole bank could reach.

When the charge FETs cut off, even with four in parallel, you still have 85V AFE chips that control the typically 60V FETS. Batts in parallel are all at the same voltage. Some batts use 80V FET's but I've yet to see a BMS, with n-channel FET's, that exceed 100V. Most budget priced batts use 85V AFE's & 60V FET's. Even if you found a batt that had high voltage FET's you'd need to find high voltage AFE's too and drop-ins just don't use high voltage AFE's.

Thanks for the clarification. Maybe I was caught up in the Series aspect. It makes sense that even in parallel the FETs would be vulnerable if they’re rated for 60V and exposed to more than that.