What are the different cell balancing methods used in battery management systems?

Cell balancing equalizes cell voltages within a pack to maximize usable capacity. Passive balancing dissipates excess energy from high-voltage cells as heat through resistors - simple but wastes energy. Active balancing transfers energy from high-voltage cells to low-voltage cells using capacitors, inductors, or transformers - more complex and costly but more efficient. Most production EVs use passive balancing due to cost, with balancing typically occurring during charging. Active balancing is beneficial for large packs and commercial vehicles with tight cycling requirements.