Originally posted by Sunking
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A BMS is the root cause of Lithium battery failures.
No two strings charge or discharge at the same rate. You are on the wrong track semi-right idea. A 100 AH Cell will have roughly half the Resistance of a 50 AH cell. No 2-cells of the same capacity have equal resistance.
It is this principal that allows strings of series cells to be placed then in parallel and charged with one charger under one charge algorithm, safely and with no issues. As long as the strings have the same chemistry and thus voltage curve, their individual capacities are irrelevant for parallel charging.
Unequal charging is not a problem for any battery type except lithium.
Top Balance is a killer of lithium cells and the root cause of failures and fires. All courtesy of the BMS. That is why EV manufactures DO NOT TOP BALANCE or ever allow the customer to ever fully charge a lithium battery. They would be sued into bankruptcy if they did on warranty claims and loss of property and life.
However, for your own edification and perhaps as material for discussion in another thread, I encourage you to go look at what Tesla does with their balancing algorithm. It happens at the top of the charge envelope, not in the middle or at the bottom.
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