Sunday, April 5, 2015

Restoring an over-discharged LiPo cell

I over discharged a LiPo 3 cell battery pack such that one cell, the middle one, read just 0.6V and neither of my chargers would charge the pack.

This is not a new problem and rather than just give up, it seems that if you're careful you can trickle charge the low cell to bring it up to a reasonable voltage for a smart charger to take over. The advice I found suggested charging at 100mA so I put a 120 ohm resistor in series with a 12V supply, put a volt meter across the cell and watched it slowly rise.

Normal voltage for a cell is 3.7 volts but I let the slow charging bring the cell up to 3.5V and now my normal charger is doing the rest.

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