BMS 4S 30A Protection Circuit with Balancing Function

This BMS (Battery Management System) ensures that when charging 4 batteries (such as the 18650) of 3.7V, all batteries are charged equally full. Suppose one of the 4 batteries is a bit older or charges a bit slower, it may need more charging time to reach the same level. The BMS takes care of this.

In addition, the BMS protects the batteries against short circuits, excessive current or voltage, etc.

Charging voltage: 16.8V
Maximum charging current: 30A*
Maximum continuous discharge current: 30A*
Short circuit protection: 75 ± 5A
Overcharge protection voltage (per cell/battery): 4.25 ± 0.05V
Discharge protection voltage (per cell/battery): 2.55 ± 0.08V
Balancing function: Yes
Dimensions: 56x45x8mm

*Note: These are the maximum values of the BMS circuit. Connected batteries may not be able to handle this current!

Pin description (See the images for the connection 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: Building a battery pack yourself requires knowledge and skill. If the batteries or the BMS are connected incorrectly, the batteries may catch fire or even explode.