Introduction ¶
Aliexpress has a great selection of battery kits. From making your own power tool batteries to unpopulated powerbanks, you can find just about anything for your 18650 cells. My dad buys a lot of old battery packs online so we have a massive collection of lithium ion cells to use for projects. These proteciton circuits are useful for adding to 18650 cells that you want to use in flashlights. The assembly is pretty simple and takes probably 5-10 minutes if you practice.
Assembly ¶
Parts (you will also need kapton tape, a spot welder, a hot air gun, and a soldering iron
First I soldered the metal leads to the board. I cut one in half and used that lead for the B- terminal. I then put the board through the plastic piece with the flat pad facing outwards. That flat pad will be the ground of the battery. I then welded the short lead to the ground of the 18650 cell and trimmed the excess metal. I masked off the area with kapton tape and the area under the positive lead to prevent shorting.
Since my battery is recycled (I tested the internal resistance to make sure it’s good) it already came with the isolating ring but if you’re using new cells put one on before welding. After that, weld the lead to the positive end of the battery (DO NOT CLIP OFF THE EXCESS). Then, route the excess metal under the metal positive cap and weld it to the cap. I placed a thick washer under the cap so that it didn’t burn my workbench. Afterwards, fold the cap back and then test for power. Finally, put the heatshrink jacket around the cell and use a hot air gun to form the jacket. And you’re done. Below is a picture guide showing each step.
Solder the leads to the board
Route the leads through the plastic piece with the pad facing outwards
Weld the short lead to the negative end of the battery
Mask off the negative terminal and path under the lead with kapton tape. Then weld the lead to the positive terminal without cutting excess
Weld the excess metal to the bottom of the cap
Fold the cap over and make it flush with the top of the battery
Put the jacket around the battery and heat up the heatshrink jacket (I used a clear jacket). And now, you've got a protected battery
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