How to make a Lipoly battery pack

by Gonzo

Here we describe the method to make a 3 cells in series (3S) Lipoly cells pack. This method can be used to build any size or type of Lipoly pack.

Before starting you have to check that all cells are in right condition, not deformed with no cuts to the external bag. Check that the tabs are not damaged and can be soldered with resin core solder (All Lipoly cells that www.RCmaterial.com sells can be soldered with a soldering iron) if not you will have to use Aluminium Solder Flux.

You have to be extremely careful and not short circuit them as this will damage them. If you do not feel secure doing it we recommend you to use Electric Tape to isolate all the tabs except the ones you are going to work on in each step.

We highly recommend the use of silicone-insulated wire for Lipoly packs.

These are the tools and materials that you are going to need:

  • A Voltmeter.
  • Double sided tape.
  • Electric tape.
  • Clothes pins.
  • Silicone wire.
  • Soldering iron, solder and wet sponge to clean it.
  • Hot glue gun (not in the picture)
  • And, of course the cells :-D

Not following the next 2 steps will result in a faulty pack, and could damage the cells and even destroy the pack on first use.

First, check the voltage of each cell.

If the difference in voltage is over 1V you can partially charge the low voltage ones or discharge the higher ones. Until you get them to match.

If you have no voltmeter, charge each cell fully separately. To make all voltages the same.

If the cells are not at the same voltage but the difference is less than 1V you can balance them by connecting them in parallel temporarily with a couple of clothespins. Be very careful to use correct polarity (all + together, and all - together).

About 6 hours connected this way will balance them perfectly. Some big cells may need more time than that.

Check at the end that all cells are at the same voltage.

Add solder to both sides of all the cell tabs.

Be careful not to short-circuit them while doing this with the soldering iron.

Bend the tabs of the first two cells like in this picture and add a little piece of double side tape to one of them.

Note: There is one (-) tab to one (+) tab.

Stick two cells together with the double-sided tape like in the picture and then solder the first two tabs.

Bend the tabs like in the picture and add again a little piece of double sided tape.

Note: It is one (-) tab to one (+) tab again.

Be careful when you stick the next cell to the side with the double-sided tape, the tabs are very close and there is risk of short circuit if not done carefully.

Solder the next two tabs and bend them over like you can see in the picture.

Use hot glue to insulate the tabs and keep them in place.

This acts as a strain reliever to keep the tabs from ripping off.

Solder the silicone wires to the two remaining tabs checking the polarity.

Again, use some hot glue to keep the tabs and wires in place.

The pack is ready for the heat shrink tubing.

Always cover the pack with heat shrink or similar material as the outside bag of the cells can be easily damaged in use.

This way you can make any size or pack type, as most of the Lipoly cells are very similar in shape.