How to recover a Lipo battery cell with an Imax B6 charger or equivalent.

If you have a Lipo battery with a cell that has discharged below 3 volts, a Lipo charger may refuse to try to charge it. For a good reason, the battery might catch on fire. Therefore the following recovery procedure is not recommended for anyone not well versed in basic electronics and especially youngsters. The procedure should only be attempted outdoors on a concrete surface away from buildings, cars and dry grass.

First determine which cell is run down. Measure the voltage of each cell at the balancing plug using a simple digital multi-meter. If the meter has pointed probes place the balancing plug on its back and press the negative lead of the meter into the exposed metal associated with the black wire. Without shorting the meter probes together, press the positive probe into the next bit of exposed metal in the balancing plug. If the meter reads below 3 volts you have found a bad cell. If the cell is badly smashed, chuck the battery.

Move on to the next cell by pressing the negative meter lead into the pin where you just had the positive lead and move the positive lead to the next wire in the balancing connector. Make note of the voltage. If above 1 volt it may come back to life.

Repeat the previous step for each cell in the battery pack. The two outer wires in the balancing connector are connected to the same points as the heavy wires. The voltage measured between the outer pins should match the voltage measured across the heavy wires. If you measure between 11 and 12 or so volts across the heavy wires but read zero volts between two adjacent pins in the balancing plug then one of the balancing leads has a bad crimp or has become unsoldered.

Now that you have found a low cell its time to give it a swift kick to get it above 3 volts so the Lipo charger will accept it. The Imax B6 charger will charge NiCad and NiMh batteries as long as they are not near zero volts.

Carefully insert pins into the positive and negative leads of the offending cell, in the balancing connector. Slip something like cardboard between the pins so they cannot short together. Use alligator clips to connect the positive and negative pins to the positive and negative main banana plug ports of the Imax B6 charger. Also connect your volt meter to the pins that are attached to the offending cell.

Turn on the Imax B6 charger and select Nicad battery and set the current to the Lipo’s rating. (e.g. 1300 mAh = 1.3 Amps). Watch your volt meter and start charging the bad cell as if it was a NiCad cell. When the voltage on the multi-meter reaches about 3.5 or 3.6 volts, STOP. Disconnect everything and connect the LiPo to the Imax B6 charger as you would normally. Try a short charge cycle then a balancing cycle to bring the battery back to a usable state rather than a full charge cycle. A charge cycle may only look at the total voltage in a pack before shutting down which could result in a cell being overcharged in the process.

Good luck.

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