Understanding your balancing loss result
Why passive balancing wastes energy as heat
Passive balancing works by routing current from higher-voltage cells through a resistor, converting the excess energy directly into heat until that cell matches the lowest one in the pack, one of the core jobs handled by the battery management system sitting on top of your pack. It's simple and inexpensive to build into a BMS, but every bit of energy bled off this way is gone for good rather than being put to use.
Why active balancing costs less energy but more money upfront
Active balancing moves energy from higher cells to lower ones instead of burning it off, typically cutting balancing losses to roughly a tenth of the passive figure. That efficiency comes from more complex circuitry, which is part of why active balancing tends to show up on higher-end battery systems rather than budget options, the same cost-versus-efficiency tradeoff the DOE's Office of Electricity weighs when evaluating storage hardware for grid-scale deployments.
Why imbalance tends to grow as a pack ages
Cells that start out closely matched can drift apart over hundreds or thousands of cycles as small manufacturing differences compound, which is why older packs often show a larger balancing loss than new ones, a degradation pattern NREL's energy storage research program tracks at the cell level across chemistries. The state of health calculator is worth checking alongside this tool if your imbalance has grown noticeably.
What to check next
Once you know your balancing loss, the round trip efficiency comparison shows how it fits into your system's overall efficiency picture alongside charge and discharge losses, and the battery round trip efficiency loss calculator breaks that same overall figure down in more detail if you want a second pass at the numbers.