[Verified] 4-string 21700 lithium battery protection board (with equalization)

The shape is adapted to the 21700 battery, which is very suitable for use in my other open source project ip5389 mobile power supply.

Just follow the parameters of each component in the bm3451 official specification, and there should be no big problem. The voltage resistance of the MOS tube should be at least 1.5 times greater than the battery voltage. The internal resistance depends on your wallet. If you have money, buy expensive low internal resistance tubes.

Update: The second version of group friend Niutou Ge (Lichuang ID: wzw666) and half a piece have been successfully verified and can be consumed with confidence

Update: The third version is released, optimized based on the second version:

1: Optimized differential current sampling and single-point grounding, making overcurrent protection more accurate:.

2: Optimized some unnecessary wiring in circles, making it more elegant.

3: Optimized the packaging of chip power supply diodes, sod123(1206)/sod323(0805) packaged diodes can be used.

4: An optional balancing indicator function is added. An LED pad is arranged in the middle of the balancing resistor pad. One of the 1206 balancing resistors can be replaced with a 0603 resistor with a resistance of 2k and a 0603 LED in series. The LED will light up during balancing. .