In a battery pack, no two cells are perfectly identical. Without balancing, small differences in voltage and capacity grow over time, and the weakest cell limits the whole pack.
Why balancing matters
The goal is cell consistency: keeping every cell at the same voltage and state of charge (SoC) so the pack delivers its full rated capacity and reaches its full cycle life. The BMS measures each cell and acts on the differences.
Passive balancing
The BMS discharges the higher-voltage cells through small resistors, burning the excess as heat. It is simple and low-cost, and is most common in residential and small commercial packs, where it runs near the top of charge.
Active balancing
Energy is transferred from higher cells to lower cells (via capacitors or inductors) rather than wasted as heat. It is more efficient and better for large, high-utilisation systems, at higher cost.
The practical answer
Most FUJI Energy systems combine BMS cell monitoring with passive balancing at top-of-charge, giving a robust, cost-effective balance between performance, lifetime and cost — with active balancing available for demanding large-scale projects.
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