What BMS do I need for a 4S 7P 12v battery?


New Member
I have purchased used scooter batteries from Jag35. I bought them for a different project I'm working on but when they arrived and I saw how they were configured, I realized that I could make a small portable power station with these pretty easily. They are arranged in a column of 5 packs, each with 7, 3300mah Full River LiFePO4 cells. They test out closer to 3,000mah, but they're in a 5S, 7P, 16v arrangement for the scooters. I realized that I could leave them in the 7P packs, but build a 4S battery with them, which should give me roughly 20AH to work with. I have 8 of the 7P packs, so I "think" I could connect those packs in pairs, creating a 4S, 14P pack that delivers around 40AH worth of power, at 12 volts.

My question is about the BMS. If you have 7P or 14P groupings, is that considered a single cell, such that a 4S, 4P BMS would work, or do I literally need a BMS for 7P or 14P? I have attached a picture of one of the 7P arrangements. There are tabs welded to the positive ends of the cells, as well. So, can this be considered "one" cell, since they're all in parallel?


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