Anyone who is into RC as a hobby knows how delicate and sometime a "pain in the neck" lipo batteries can be. Its common in the hobby that lipo battery packs such as 2s/3s/4s and so on can have single cell failures which results in some people just throwing the whole pack away and some of us that are more enclined not to throw anything like that away cut them apart and either replace the cell or just remove it.
If you have search online for a boken off tab on a lipo battery most say it cant be fixed, toss it in salt water and throw it away! When were paying upwards to $80 for a good 3s lipo I refuse to "Throw it away", so lets try this idea instead.
Step 1: Materials
I had some thin copper sheeting usually used for embossing laying around that I used. I origionally bought this to fix larger PCB traces so I just went with that.Its easy to cut and shape so it really worked well for this mod, but I am sure if you had Tin or something else would work also as long as solder will stick. Here are some good examples of metal thats solderable :
Fair- Copper Bronze Brass Lead Nickel silver Beryllium copper
Excellent- Tin Cadmium Gold Silver Palladium Rhodium
* 38 guage copper sheet
* Small exacto knife
* Needle nose pliers
* J B Weld
* Small putty knife & mixing tools etc.
Step 2: Battery Surgery
The first main step is take the broken side of the lipo and make a small slit with the exacto knife about 2mm under the seal so your going through the metal tab inside the lipo. See the picture.
Be very carefull not go down to close to the battery body itself or it WILL get hot and catch fire which will suck! This is by far the most intricate and delicate step of this instructable. The slit has to be about 2/3 of the battery tab width.
Step 3: Copper Tab
Next we are going to cut a strip off the copper about 2mm WIDER than the slit you just made. The reason for this is because there must be zero, no play at all were the copper makes contact inside the battery tab, this way we can ensure our metal will be making good, snug contact with the new copper tab. I used small pliers and gently but firmly pulled the copper tab through the slit until even amounts on both sides. Once this is done fold copper up until it meets together and "sqeeze" with your needle nose pliers tightly together. See pictures above, they are in proper order .
Step 4: Seal With J B Weld
Next we take the Jb Weld and mix enough to seal BOTH sides of our new battery tab slit. Sealing is probably the most important step because if it does not seal the battery will not charge, so take your time and do a good, careful job.
The pictures above you can see that I used a small putty knife to cover and smooth out the epoxy (JB Weld) and check closely to see if you sealed the area all the way around, even over the top and around the other side just to be certain the seal will not leak.
Set aside somewhere that it will not be accidentilly hit that could disturb the hardening process of the epoxy. I waited about 16 hrs for mine and it turned out hard as a rock. Above are other batteries from 3s packs that broke. I am soldering them later to re build 3s packs.
Step 5: Checking Our Work!
Now that we have waited 16-24 hrs for the JB weld to dry and harden,we can start charging. I made a usb charger with an red/green led inside from an old toy drone that charges single cell lipos and just added alligator clips to easily charge the lipos with tabs.
Hopefully you will have a fixed lipo reading 4.20 v now that was destined for the trash. I have always saved my broken lipos so now I can start making some 3s packs for my drones and planes. Hope this works for you!
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