Salvaging/Repair/Disposal of faulty lipo batteries

 

I have been using two of these batteries in my ebike for over 6 years and recently a single cell was getting hot when charging, also it would not charge above 3.97v whereas the other cells would charge to the optimal 4.2v. I sense a problem here. I decided to inspect the pack.

Here we begin outside the house for safety reasons, and we strip off the outer packaging to reveal the individual cells.

Once we have the packaging removed we can see that all the cells are not stuck together and just fanning out. This should make removing of any faulty cells easy. The battery is officially a 6s lithium polymer battery, however when we remove the packaging we reveal 12 cells which are wired as pairs to make a 6s battery. each cell is therefore 8000mah 1s 4.2v, two of these cells in parallel make 1s 4.2v 16000mah. as a 6s battery it gives us 25.2v (6x4.2v) at 16ah.

 A typical individual lipo cell albeit in a large capacity.

After inspecting the faulty battery pack I observe that a single cell has a puncture which has somehow sealed itself with leaked lithium. I should consider this a lucky thing as it has decided not to inflate or explode and I was able to remove and isolate the faulty cell from the rest of the pack thus reducing overall potential failure risk. I placed the faulty cell into a lipo safe outdoor container and discharged the cell to zero volts making it inert and safe.

 This leaves me with a 5s 16ah lipo battery. Which as yet I am unsure what to use it for. Maybe I will split the cells and make two 5s 8000mah lipo packs, or one 6s 8000mah and one 4s battery.

The battery is safe now that the faulty cell is removed, and I wrapped the pack in kapton tape for added protection.

 Some tips:
-Always regularly inspect your lithium batteries for visible damage.
-If there is visible damage remove the battery from indoors and place outside far away from anything which could burn.
-If the cell pack is hot on one side and the lithium charger shows a single cell refusing to charge to 100% then take this as a solid indicator of battery damage.
-If you have confidence in your abilities remove the damaged individual cell as soon as possible to isolate it from the other lithium cells.
-Dispose of the damaged lithium cell by discharging it safely using a battery discharger to make it inert.

I am yet to experience a lithium battery fire and I have over ten years of experience using lithium batteries. However consider this that the older and more used the lithium battery is the more the chance of cell damage, poor condition, poor internal resistance, and therfore higher chance of problems. We are approaching a time where hobbyists are in posession of more and more older batteries which need to be carefully disposed of and there are not the facilities out there to assist with disposal which leaves the responsibility on us the user to find a safe and suitable plan for safe discharging and disposal so perhaps it is time to start your own journey into safe lithium battery disposal now and consider refreshing your old batteries with new.

Thanks for reading.

High-power Lipo Discharger

 

I decided to build a Lipo discharger this week. Most off the shelf products were expensive and underwhelming for my needs. I am attempting to discharge a 6s 16ah 24v Lithium Polymer battery which has recently had cell issues after 6 years of regular use. Instead of throwing it away carelessly I wanted to empty the battery of all power therefore making it inert.

 

I have seen some homemade battery dischargers on the internet which use 50w 12v car light bulbs in an array to increase the amps pulled from the battery thus emptying it more quickly. It should light up your space like a lighthouse. These bulbs can be bought for approximately £4 each.

Other options I have considered are Industrial Resistors which are often used in home wind generator setups to help dump the load when the wind is too high and the power generated too great. The power has to go elsewhere so a large capacity resistor can do. Typically a 24v 300w resistor costs around £25.

Another interesting option I thought about was my final idea. I found via the internet that there are super cheap 12v/24v immersion heaters for car vehicle 12v sockets. They are used to heat a cup of water in your vehicle so you can have hot tea or coffee. After a few rudimentary tests I found the immersion heater to draw 220 watts of power without melting the cable or plastic. I found them for sale at £4 each. 

 

So I decided to buy 4 of these DC water heaters:

4 x 220 watts = 880watts of discharge power

 

The commercial 200 watt lipo discharger is around £70, so we can discharge 4 times higher than this.

I wired the heaters up so that i could have two or four connected to allow variable discharge rates.

I also included an emergency stop button in the event I need to stop the discharging cycle for some reason.

When it is time to discharge the lipo I place the immersion heaters into a glass bowl of water and let them heat the water, it is a plus if boiling point for tea is achieved.

Thanks for reading.