Lipo batteries degrade over time, sometimes this degradation results in dead cells. It seems to be a waste to throw the whole pack away because other cells might still be working. In this post we will show you how to make a working LiPo by combining the good cells from multiple damaged/defective batteries.
Warning: LiPo batteries can be dangerous, please understand the risk before doing this DIY hack. If you are doing this hack, you are doing so at your own risk, the author and OscarLiang.com are not responsible for any fires or damage caused.
The Lipo batteries have to be the same brand, capacity and discharge rate for maximum safety and performance. Do it outdoor if you can, wear a pair of safety glasses just in case :)
Following this guide to dispose LiPo batteries.
What you need
- Multiple LiPo batteries with dead cells (with enough good cells to make a working battery, for example for a 4S LiPo you need 4 good cells)
- A multimeter to check battery cell voltages
- Wire cutter
- Stanley / Craft Knife
- Soldering iron (recommendations)
- Hot Glue or Liquid Tape
- Electrical tape
- 80mm PVC heatshrink tube/sleeve
- A big bucket of sand to put out fires (just in case!)
- Do this outdoor if possible to avoid burning the house down, or filling your house with toxic gasses from LiPo fire
Step 1 – Removing packaging
Remove the exterior plastic packaging from the LiPo battery. Make sure you are cutting on the side with the internal protective layer. This thicker flexible layer will help ensure that you do not puncture any of the cells with your knife.
Step 2 – Separating the bad cells from the good
Separate the good cells from the bad. When taking the cells apart, working in a warmer room help separating them more easily because the adhesive is less sticky when warmed up.
Use a multimeter to determine if the cell is bad or not.
If the cells next to each other are good, then you don’t need to separate them, just leave them stuck together.
I also mark the good cells with “OK” in case I forget which is which :)
Step 3 – Putting good cells together
Check with a multimeter which terminals are positive and negative, remember the cells must be wired back together like this: + to – to + to – to + to – to + to –
Then I solder the cells side to side in series: + to – to + to –
Step 4 – Soldering wires
When soldering on batteries terminals, you need to be extremely quick, and use lower temperature for soldering. Don’t overheat the battery, otherwise it might cause a fire if you are not careful.
- Solder the main connector lead (XT60) to the Lipo cells, red to cell 1 positive, and black to cell 4 negative (as shown in Pic 1)
- Then the balancing lead following the wiring schematics diagram above. Starting with negative wire: first black balance lead connects to the negative of the 4th cell. (Pic 2)
- 2nd black lead goes to – of the 3rd cell, or the + of the 4th cell (Pic 3)
- 3rd black lead to – of the 2nd cell, or the + of the 3rd cell (Pic 4)
- 4th black lead to – of the 1st cell, or the + of the 2nd cell
Lastly, the red balance lead goes to the + of the 4th cell. Then secure the solder joints with some hot glue.
Step 5 – Final check and re-packaging
Check the voltage of the discharge connector, as well as the voltage of the balance plug, make sure each cell is reading the correct voltage.
Get some PVC heat shrink sleeve for re-packaging (80mm heat shrink is great).
You can remove and save connectors / balance lead from old or dead 2S or 3S LiPo’s. If you have a 4S with a dead cell or two, you can convert them to a 2S or 3S pack. They are great to be used with your FPV goggles and TX.
- May 2016 – Article created
- July 2018 – Updated
Credit: Hans Turpyn