Maximizes Capacity: Balanced cells ensure that the battery pack can achieve its maximum rated capacity, as the weakest cell determines the overall performance. Prolongs Lifespan: Preventing individual cells from being overcharged or over-discharged extends the lifespan of the entire battery pack.
When are battery pack cells balanced?
Battery pack cells are balanced when all the cells in the battery pack meet two conditions. 1. If all cells have the same capacity, then they are balanced when they have the same relative State of Charge (SOC.) SOC is usually expressed in terms percent of rated capacity. In this case, the Open Circuit Voltage (OCV) is a good measure of the SOC.
What is battery balancing?
Battery balancing equalizes the state of charge (SOC) across all cells in a multi-cell battery pack. This technique maximizes the battery pack's overall capacity and lifespan while ensuring safe operation.
From a State of Charge (SOC) perspective, without balancing, the SOC range is typically limited to 20% to 80% for safety reasons, providing only 60% usable capacity. With balancing, the SOC range can be expanded from 5% to 95%, increasing usable capacity to 90%. This means the battery pack's usable capacity is significantly enhanced.
Since charge and discharge cycles times can be shorter than the initial charge time, this process demands higher currents. Therefore, it is a much more demanding issue. When the cells in the battery pack are not balanced, the battery pack has less available capacity.
In an unbalanced battery pack, during charging, one or more cells will reach the maximum charge level before the rest of the cells in the series string. During discharge the cells that are not fully charged will be depleted before the other cells in the string, causing early undervoltage shutdown of the pack.
Common multiple cell configurations for Li-Ion cells in battery packs consist of three or four cells in series, with one or more cells in parallel. This combination gives both the voltage and power necessary for Portable Computer, medical, test and industrial applications.