Quick Answer
If balancing systems fail in a battery pack, you should disconnect the pack from the charging source and any loads, and then use a multimeter to check the voltage of each cell to identify the failed cell. Compare the voltage readings and remove the failed cell from the pack. Rebalance the pack by recalculating the charge limit for the remaining cells.
Identifying the Failed Cell
When a balancing system fails, it’s essential to identify the failed cell before taking any further action. Use a high-accuracy multimeter to measure the voltage of each cell in the pack. Compare the readings to ensure they’re within the acceptable range (usually 2.5V to 2.7V for lithium-ion batteries). If you find a cell with a significantly lower or higher voltage, it’s likely the failed cell.
Removing the Failed Cell
Once you’ve identified the failed cell, disconnect the pack from the charging source and any loads. Use a multimeter to double-check the voltage of the failed cell to ensure it’s not a temporary issue. If the cell’s voltage remains abnormal, remove it from the pack. Take note of the cell’s position in the pack and the connectors used to connect it.
Rebalancing the Pack
After removing the failed cell, recalibrate the charge limit for the remaining cells to prevent overcharging. Use a battery management system (BMS) or manual calculations to determine the new charge limit based on the number and capacity of the remaining cells. This ensures safe and efficient operation of the pack.
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