3s 18650 12V Li-ion Battery

I wanted to have a cheap Lipo 12V battery for my water pump. I decided to make my own by using

In addition, I used a Leatherman, soldering iron and solder, duct tape and a JST plug.

Step 1: Prepare the Batteries

  • Put the 18650 battery in the battery box
  • Make sure that you set them in correctly - check polarity!
  • You will need 3x 18650 battery boxes.

Do not mix the good battery and poor battery to use!

Step 2: Solder the PCB

  • Now you need to solder the batteries to the PCB
  • Black wire is ground/negative, red wire is plus power.
  • Keep strictly to the diagram wiring: 0V/4.2V/8.4V/12.6V,Otherwise it will cause damage to the chip!

Step 3: Finish the Battery

  • Solder a connector plug to the output of the PCB. I used a JST connector. However, you are free to use other connectors like XT60.
  • Now the battery is working. If you like you can use duct tape like me to keep the 18650 boxes and the PCB together.
  • I use the battery to power a 12V water pump.



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7 Discussions


3 months ago

I made this & I think that covering the components with tape might make them overheat.
Using double faced tape to mount the board, that would let them breath.
This used 6 LG 18650 batteries, I have tons of different manufactures good batteries laying around.
Now to find uses for the rest!


5 months ago on Step 3

These cells are not LiPo so perhaps you should rename this! This would never deliver the power of a genuine LiPo battery.

1 reply
Carl Stone

5 months ago

Great Job! :D
I have a question: how much amps delivers it?

2 replies

5 months ago

If you use 18650 batteries but LiFePo4 types of 3.2V nominal you would be able to use 4 cells and your voltage would be around 12.8 to 14 Volts max. Have a look at this site that deals only with that technology. Much safer too