DIY Lithium Battery Pack Repair for Solar Lights

If you're interested in DIY lithium battery packs, this article might be helpful.

The battery of a 15AH, 3S5P 18650 battery pack used for solar lights was damaged. After disassembling and inspecting it, 9 cells were found to be defective, leaking or with no capacity. The remaining 6 cells tested with a capacity between 1400mAh and 1600mAh. So, what should be done?

You can prepare two power banks: one with 20,000mAh and one with 10,000mAh, along with three 3.7V, 10Ah, 10,000mAh polymer lithium batteries.

These three batteries can be arranged into a 3S 11.1V battery pack. The protection board can be taken from the damaged pack, and the welding and assembly are quite simple:

Use the shell of the 20,000mAh power bank and add one more cell. If the cover doesn't fit properly, you can pad it a little, then secure it with tape. Once that's done, perform charging and discharging tests to make sure everything works fine.

The lithium battery pack should now be ready.

Finished!