I received a Turnigy 3S lipo that read 7.68v new out of the box. One cell was at 0.28v. I have a charger that charges only thru the balance wires and after spending about 10hrs on that charger, it got the low cell all the way back to 4.2v. Its been OK since.

All you need to do is ID which wire goes to the low cell off the balance tab and then rig something to charge it. Unfortunately, its easier said than done. If you have a male servo connector, that makes it easier.