BMS 4S 40A Li-Ion Lithium Battery 18650 Charger PCB

A Battery Management System (BMS) for a 4S battery pack. With this circuit, you can safely create a battery pack of 4 series-connected Li-ion/Li-Po batteries (cells). The circuit protects the battery pack against short circuit, overvoltage, and undervoltage. Additionally, the circuit ensures that the batteries are charged evenly (balancing function).

Specifications:

Charging voltage: 16.8V - 18.1V
Maximum charging current: 25A*
Maximum continuous discharge current: 40A*
Short circuit protection: 45 ± 5A
Overcharge protection voltage (per cell/battery): 4.28 ± 0.05V
Discharge protection voltage (per cell/battery): 2.55 ± 0.08V
Balancing function: Yes
Dimensions: 56x45x2.6mm
*Note: These are the maximum ratings of the BMS circuit. Connected batteries may not be able to handle this current!

Pin description (See the images for the wiring diagram):

B-: Minus cell/battery 1
B1: Plus cell/battery 1, minus cell/battery 2
B2: Plus cell/battery 2, minus cell/battery 3
B3: Plus cell/battery 3, minus cell/battery 4
B+: Plus cell/battery 4
P+: Plus output battery pack
P-: Minus output battery pack
Use the P+ and P- connections to charge and discharge the battery pack.

Note: Assembling a Li-ion/Li-Po battery pack requires expertise. Only assemble the pack if you know what you are doing. Incorrectly connecting the batteries and the BMS circuit can cause the batteries to catch fire or even explode.