Proper Battery Build w/BMS

Joined
May 21, 2022
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I just finished my second Battery build. It is a 13S 3P combo using 4500mah 21700 Lishen cells. That gives voltage of 54.6 & amp-hrs of 13.5 for a capacity of 737 watt-hours. I am posting a couple of pictures of the silicone wiring {except BMS sensing}. There is a UL flame-resistant thin plastic barrier between the top of the battery & the aluminum of the BMS heatsink. Common port BMS wiring is drilled down thru the black battery mounts to the necessary bottom connections. Wiring is fastened with 411 cyano adhesive to the plastic cell holders & ty wrapped to larger battery cables. All of this fits into flame-resistant thin plastic case {shown in a previous battery post}. Hope this gives some builders a good idea of a safe lithium-ion battery build.
 

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I've also built a 13S-3P pack out of Lishen cells. I used LR2170SF, rated for 4500mah and 13.5A. So it's a nominal 48V13,5ah pack, but the battery tests out at 11.8Ah @ 3A with a load tester, suggesting 3900 mah for the cells in real life on an ebike, My comments follow.

-I applaud the use of cell spacers. I also use them. Expands the size slightly, but so will the final padding and box around the battery. It may be silicon wire, but that's a lot of wire to loop over the top of the cells. Just a cosmetic detail.

-I believe those are white vinyl washer the positive ends of the cells?. All commercially made packs I have use them, and so do I. More than once, a washer has saved me when I put the welder tips down wrong and there was air underneath instead of the positive metal.

-My main critique. Each series group connects to the next with only one tab of nickel. I would have used three. That's potentially 30-36A forced thru the middle. If you're using 10 mil x .20mm nickel, one piece was not meant for 30A.
 
One other constructive criticism is that you should better isolate the balance leads:

2022-12-10 09_14_15-file.php (936×279).png

In locations like this the wires could rub through due to bike bouncing, vibrations, etc, and create a short.

Overall, for a build like this it would be better to pull nickel over the edge and have the balance system on the side instead of on top of the cells. For example:

2022-09-26 10.30.42.jpg
 
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