Designing one BMS for each lithium-ion battery pack is necessary.
If the batteries become unbalanced over time, one has more charge than the other, and the charger will overcharge the battery at the end of charging, which is prone to accidents. The right BMS would not be too expensive. Depending on your situation, two cells are connected in series to form a battery pack, which we will call a 2S1P battery pack, and you can buy a BMS with the 2S1P tag.
MORE: Is it possible to connect two lithium-ion batteries in parallel with a separate BMS?
