4S 40A Li-Ion 18650 lithium battery charger and protection board module for building and protecting 4-series lithium battery packs. Suitable for 18650 battery packs, DIY battery projects, power tools, robotics, backup power systems and electronics battery protection applications.

Helps provide lithium battery pack protection functions such as overcharge, over-discharge and short-circuit protection, depending on the battery pack design and wiring. Commonly used as a 4S BMS protection board for 14.8V nominal / 16.8V fully charged Li-Ion battery packs.