BM3451-5 string lithium battery balancing protection

~~Currently, the board has not been tested and the project has not yet been verified~~.
The schematic diagram is designed according to the chip technical manual. Two pads (P+, P-) are manually added to the PCB to serve as charge and discharge input and output interfaces (no devices in the schematic diagram are P+ and P- two Nets);
both the schematic diagram and the pcb are Correct (the cover is a 3D preview);
     when using it, you should pay attention to selecting a mos tube with appropriate parameters. The output line in the main circuit is 3mm wide. You can choose batteries with stronger discharge capacity according to personal needs,
and thicken (window) 3mm wiring.
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**Project progress update on August 23, 2022**:
1. The project has been board tested and no bugs were found. Testing The function is consistent with the expected results;
2. The proofing is to order 5 circuit boards through the Jialichuang platform, with some resistive components attached + PCB + freight = 1.07 yuan (free +1);
3. In the project, a capacity with a certain capacity is deliberately used The reduced battery cell (the poor one on the far right with its coat stripped off) was charged in parallel to 4.1v before welding. After
      welding to the balancing board, the phenomenon was as expected: when the charging current was 0.1A (because the battery was already close to
      The discharge indicator light on the rightmost side lights up first and starts discharging .

~~![The PCB.JPG of some components has been bandaged]           ** It only cost 1.07 for the components, which saved me half an hour of looking for tweezers, solder wires, components, and soldering one by one! **

**![IMG_8682.JPG]         The brighter the light, the higher the voltage, and the higher the discharge pwm duty cycle!
![IMG_8683.JPG] Fill in the voltage and current settings during charging (5 strings fully charged are 4.2X5=21v).


  I tried it and it can power the T12 soldering iron. (I forgot to take a photo)

**Written at the end: In fact, there were already 6 string equalization boards before this project, but two BM3451 cascades were needed. **
Personally, I think that one chip can do 5 strings, and using two chips to make 6 strings is really a bit wasteful; and if the T12 is powered by 21v, there is no problem at all, which also saves a chip and some parts. cost.
                 ~~~~