Many 2S Li Ion battery pack uses a BMS circuit to protect the batteries inside the module. Unfortunately, the BMS constantly draws power for the batteries despite being at a very low uA level. Over time, the BMS can deplete the battery enough to drop below the BMS cutoff voltage which is typically around 5.9V for a 2S Li Ion pack. Once the module voltage drops below the BMS "bricking" voltage, the battery pack will be rendered useless and can no longer be charged. The module could be revived by charging at a very low current (< 15 mA) for many hours to days to get it back above the threshold. This is also not good for the Li Ion battery chemistry itself when it's at a very low "depleted" voltage.

This battery cutoff management circuit uses an IC from Analog Devices Inc. to do the battery threshold voltage check. Therefore this board requires no firmware programming. It will automatically shut off the power to the load when the battery pack voltage drops below a certain "safe" voltage. The voltage can be changed by changing the associated passives (C and R). The threshold is 6.2V in this design and this will allow many months of the module to be in the "depleted" state before hitting the bricking voltage of the BMS. The board allows up to three 2S battery modules.

The battery module is designed for our passive acoustic recorder, which draws very low current (< 30 mA),) and this circuit might not be suitable for a high current battery pack.