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Motorola Phone Battery BMS Terminals
#11
the problem is whem low voltage disconnect occurs.
the whole string voltage is placed on the now turned off mosfet.
it may not be designed to withstand this.
(07-24-2019, 01:48 PM)Korishan Wrote: I don't see why putting them in series would cause a problem. If 1 turns off, voltage stops. No cells within the string would see full voltage. After all, a battery cell doesn't see high voltage if another is disconnected.

However, you could take 3 units and connect them in series and put a load on the whole string and monitor each pack voltage and temperatures.

In another since, you could always just completely disconnect the bms all together. But that would require opening up each pack to remove the bms board.

Trying to charge by bypassing the bms, with it still connected, could be very difficult, depending on how the bms is designed. It might be designed that if it senses power flowing backwards, it shuts down to protect the cells. Can you take one of the boards out so we can see what the other side looks like?
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#12
Progress Update,

as they say the best laid plans of mice and men. I have got a little bit smarter about how I break up these packs and I have developed a technique that involves the judicious use of a hand held hacksaw blade. I am getting both 18650 and 18500's from these packs without damaging them and they have gone on to the test bench. Some have excellent voltages. In the end I think its just easier to pull them apart. The good news is I am starting to build my first bank. Slowly.
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#13
While pulling them apart is more work, you then get to design everything exactly as you want.
I think you also remove some risk that things go wrong in an unexpected manner.
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