A Battery Management System (BMS) protects lithium battery packs and maximizes life.

What a BMS Does:
1. Overcharge Protection: cuts at 4.2V per cell
2. Overdischarge Protection: cuts at 2.5-3.0V per cell
3. Overcurrent Protection: stops excess current
4. Short Circuit Protection: instant cutoff
5. Cell Balancing: keeps cells at equal voltage
6. Temperature Monitoring: prevents overheating

BMS Types:
- Passive Balancing: bleeds energy from high cells
- Active Balancing: transfers energy between cells

For DIY projects, use off-the-shelf BMS modules matched to your cell count and current needs.