Lipo Cell Replacement Question

[BlackSnakeRacing]

Over the last few years i have been repairing my lipos, replacing balance plugs if broken off, removing dead cells to make smaller packs or replacing cells from other packs that have been seperated. Usually i find these things when the pack has been run down to LVC (or close to) and my spare cells have been stored at 3.8V. Now the other day i had a cell in one of my Nano-Tech packs fail to take a charge, which means the other 2 cells in the pack are at 4.2V. Should i discharge the 2 cells down to 3.8V before replacing the dead cell, charge the single cell up to 4.2V, or just replace the cell and balance charge to bring them up to the same level? Me in my infinate wisdom has already removed the dead cell from the 3S so i will need to solder leads on to discharge, or soldier leads to the replacement to charge.

[785boats]

When ever I replace a cell in a pack, I discharge the pack down to 3.7V or 3.8V per cell & get the replacement cell down to the same level. Less potential energy if you do happen to short something out.

[BlackSnakeRacing]

thats what i thought, wanted to take the easy way out and do the single cell up to 4.2 though as i only have to solder one lead to do that, and touch wood i havnt shorted anything out yet while soldering (shorted a cell accidently when i bumped it onto a metal hobby knife handle so have been REALLY careful ever since)

[785boats]

It is probably not so critical if you are replacing an outside cell with only two tabs and one wire to play with. But if you are replacing an inside cell of a 4s or 6s pack there's a lot more de-soldering & soldering to do & more chance of shorts. I'd get into the habit of bringing all cells down as low as you can first.
But please... wear safety glasses when ever playing with these things, whether they're fully charged or discharged.

All the best.
Paul.

[BlackSnakeRacing]

Thanks for the advice mate, safety glasses are on when ever i am soldering, regardless of if it is batterys or just adapter leads. Will run them all down to storage and then repair the pack.

Cheers