From Unofficial Zero Manual
For battery packs that are built as a stack of cells, like Zero's Brick core battery pack unit, cell balance indicates the maximum difference in per-cell voltages, that is the difference between the highest voltage cell and the lowest voltage cell.
- Cell imbalance means a high difference in voltages, and is the inverse of cell balance. Cell balancing reduces cell imbalance.
- A cell at a lower voltage will operate worse than one at a higher voltage, and an EV must operate with all its cells above a certain amount to avoid a risk of premature chemical and thermal wear on the cell.
- So, a higher level of cell imbalance will lead to the battery pack having a cell reach a lower voltage limit sooner than one with relatively balanced cells.
- Symptomatically, this means that the bike will experience a torque reduction at a higher SoC if cell balance is poor.