Battery Balancing

Battery balancing covers the techniques used to even out the charge levels of the individual cells in a multi-cell battery pack, improving the pack usable capacity and extending each cell life. Because manufacturing differences, aging, and environmental conditions cause cells to drift apart over time, an unbalanced pack is limited to the capacity of its weakest cell, since charging must stop once any one cell reaches full voltage and discharging must stop once any one cell empties, and a badly unbalanced cell risks permanent damage or thermal runaway. Passive balancing dissipates the extra energy from overcharged cells as heat through resistors, while active balancing instead moves energy from fuller cells to weaker ones using capacitors, inductors, or DC-DC converters; active balancing is more efficient but adds cost and complexity. Both methods are common in the lithium-ion battery packs used in laptops, electric vehicles, and power tools. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/