The 5S 40A 18650 Li-ion Lithium Battery Charger Protection Board is engineered for 18.5V (nominal) and 21V (fully charged) battery packs. It offers overcharge, over-discharge, overcurrent, and short-circuit protection with high current handling of up to 40A. Equipped with cell balancing, it ensures stable voltage across all series cells, enhancing battery performance and lifespan. Ideal for e-bikes, power tools, and high-drain devices.