2Pack Enhanced 4S 40A 16.8V Li-ion Lithium Battery Protection Board PCB BMS Charger Protection Circuit Balance Charging Module for Drill Motor Motorcycle Battery (4S 40A)

Works well, used 4 x 18650 li-ion cells together for a drill. The two boards were connected together on arrival but easily split apart by bending slightly. Installed in my drill and charged up to full power. Tested the drill, it works fine, have not used it for any projects yet though. Will update review if have any problems.

Exceptional value and service. Thank you

Needs better instruction on how to connect it up. Made mistakes and blew two boards. Seems to work okay when connected properly.

I bought this to prototype a pack, and while it seems to balance my cells, and is easy to use, there no way it can handle 40A as stated. At even short bursts of about 25A some of the components on the board are toast. It’s not exactly a knock against the board, it works fine at lower currents. Just know that you’re probably safe in the 5 amp range.

I installed this and found that 2 cells charged to 4.22v and 2 charged at 4.10... BAD BMS functions when it suppose to balance them within .02 V. Using this will destroy your batteries.. BUY something else. CHINESE cRAp

Doesn't protect from overcharging or balance cells. Not sure about undervoltage protection but got my 4s pack up to 17.8v and it never cut power

They don't work to good they ok for low amps try to pull more they 5 amps they shut down

I ordered the 2Pack, but only received 1. The Amazon App does not provide a way to resolve this.UPDATE: The board I received is actually 2 circuits on the same board - not what the product picture shows.