Lipo Balance Lead Repair
If you partake in anything RC, chances are that this has happened to you. If you're like me, you probably know that it's fixable, but thought it wasn't worth the trouble or risk involved to repair it.
In this quick tutorial, I will show you not only how easy it is to repair, but how with certain simple precautions, it can be quite safe.
*WARNING* ALTHOUGH I JUST SAID THIS IS QUITE SAFE, BECAUSE THIS IS WILL REQUIRE DISMANTLING A LIPO BATTERY (WHICH IS INHERENTLY DANGEROUS AND COULD CAUSE A FIRE), PLEASE ONLY ATTEMPT AT YOUR OWN RISK.
Step 1: Getting into the battery
Cut off the shrink wrap around the outside of the battery.
Using a sharp utility knife, cut into the wrapper of the front or back top of the battery below the wire level and above where the battery goes flat. Be careful not to go so deep that you contact the battery cell. This does not take much pressure.
Carefully peel back the wrapper to reveal the wire solder points. Note the wire I had come off is on the second layer below the yellow Kapton tape. Usually, the wires tucked furthest into the battery don't come apart as less tension is put on them.
Tip: Now is a good time to check all the balance wires to see if any others are getting close to failure.
Step 2: Accessing the balance solder pad
Tape off the open contacts that you aren't modifying to prevent shorting. This is one of the steps that, if skipped, create an unnecessary risk. Any metal shorting 2 points will likely cause a fire.
Slice open the Kapton tape as shown and peel it out of the way. Then isolate the final unneeded solder pad.
Step 3: Wire prep
Strip and pre-tin the loose wire and the solder pad of the battery. This is an important step. It will make the melting of the solder happen quicker and won't heat the battery up as much. (The other risk involved)
Step 4: Solder the wire to the pad
Solder the wire to the pad. Be careful not to hold the soldering iron on the battery longer than necessary. I find it easier to use a hot tip (750-800F or 400-430C) because the quicker heating lets less heat transfer far into the battery.
Tip: You could add hot glue over the contacts. This almost guarantees it won't happen again.
Final Step: Put it back together
Tip: Try to reuse the original Kapton tape but if it is compromised in any way, don't rely on it.
I added electrical tape anyway to be safe.
After all the contacts are well covered, fold back the main wire wrap and tape it to secure it.
Test to be sure all your sells are being registered at the balance lead.
And now... Fly Fly!