[Verified] Makita interface power tool lithium battery protection board (based on BM3451)

## Update history:
23/1/10 V1.1: Add TVS surge protection
23/6/10 V1.2: The pin welding hole is narrow, which has been changed (during actual measurement)

# Important reminder!!!
**Lithium battery pack assembly is dangerous, so you must fully learn the relevant knowledge or carry out the work under the guidance of an experienced person!!! **
**Lithium battery pack assembly is dangerous, so you must fully learn the relevant knowledge or carry out the work under the guidance of an experienced person!!! **
**Lithium battery pack assembly is dangerous, so you must fully learn the relevant knowledge or carry out the work under the guidance of an experienced person!!! ** **
Be sure to use better batteries! Do not use inferior batteries of unknown brands! Otherwise, the equalizing resistor will be overloaded and overheated and burned! **
(Important things should be said three times)
Also, if you encounter any problems, please search Baidu first, and do not post them in the comment area as soon as you have a question. Ask again if you can't find it!

# Production steps
## 1. Material preparation
Protection chip: [BM3451-TDNC](https://detail.tmall.com/item.htm?_u=t2dmg8j26111&id=607958863275&spm=a1z0k.7385961.1997985097.d4918993.64ba37dehkGjmA) (Please click the font directly to open the page, the same below)
MOS: [CSD18540Q5B](https://item.taobao.com/item.htm?spm=a21n57.1.0.0.14a6523cWeDaeH&id=663046959853&ns=1&abbucket=0#detail)
(It is more expensive. You can use other NMOS with the same package instead. Pay attention to the parameters. The withstand voltage should be at least 30V)
Current sampling resistor: [5mR alloy resistor](https://item.taobao.com/item.htm?spm=a1z10.3-cs.w4002-17890096034.20.5a973600SLHOLC&id=40975789391)
Balanced discharge resistor: [1206, 20 ohm resistor, unlimited accuracy](https://item.taobao.com/item.htm?spm=a1z10.3-cs.w4002-17890096034.28.1ba23600LwLUn m&id=579574749910)
Battery balancing NMOS tube: [AO3400](https://item.taobao.com/item.htm?spm=a1z10.3-cs.w4002-17890096034.10.5a2f3600jT2D8T&id=38218469610)
Charging PMOS tube: [NCE30P20Q](https://item.taobao.com/item.htm?spm=a21n57.1.0.0.2826523cpJtAh2&id=660710351687&ns=1&abbucket=0#detail)
(If you think it is expensive, you can also use a PMOS with the same package as the one you already have. Pay attention to the parameters and the withstand voltage should be at least 30V)
TVS tube: [30VTVS tube](https://detail.tmall.com/item.htm?abbucket=0&id=625229346386&ns=1&skuId=4428754601393&spm=a21n57.1.0.0.2826523cpJtAh2)
NTC热敏电阻：[NTC热敏电阻](https://item.taobao.com/item.htm?id=653184793260&ali_refid=a3_430582_1006:1291110145:N:UJj6NX6oyIakE7OTbuXziA%3D%3D:1bec171ab627128f14931b6ad527cddc&ali_trackid=1_1bec171ab627128f14931b6ad527cddc&spm=a21n57.1.0.0#detail)
（请选用100K,B值3950,环氧树脂型号，如果觉得贵，亦可以选用相同参数其他店家或根据规格书和手头已有热敏电阻自行计算）（此原理图中，过热保护温度为45度）
There are many SS34s on Taobao. Just buy the SMA type.
The other original parts models and parameters are marked in the schematic diagram. The remaining RCs are all in 0603 package!
I am a personal player, please forgive me for not having BOM! ! ! ## 2. Front and back
of the board after boarding: ![Double-sided picture.png] ## 3. Welding battery connection diagram: ![Cable connection diagram.png] Actual picture: ![Actual picture] **(The battery used in the picture is SONY (actually it has been sold to Murata, and it is still customarily called Sony) VTC6C 2600mah. If you want to replace other batteries, please choose high-quality power batteries from Samsung, Tianpeng, Haisida, Dongmei, Yiwei Lithium Energy, Changhong Sanjie, etc.)**