I have a HXT 3s 620 mAH pack that one of the cells went out on me. It still hold some charge, but after fully charging my battery that single cell drops from 4.2charging to 4.03v and is very lightly swollen while the other two maintain ~4.17 volts Letting it sit a couple minutes it drops down to 4.01 volts. Should I continue to use it as a 3 cell or will the 1 bad cell damage the other 2 in use? I could disconnect the bad cell and use the two good ones because I had already planned on buying a couple of the same sized 2 cells.

What do you think? 2 cell conversion or still usable as a 3 cell?

Are you talking static voltage , or voltage or load? THe other 2 cells can have apparently normal static voltage, while the on load voltage is equally bad.

My routine is to put the 3s on load at a specific current. Then measure the voltage of each cell. If only one cell get bad, I willl see if I need any 2 cells pack, say for BEC usage, and resolder to 2s. It is often difficult to get another single cell to resolder to a 3s as it the 3s pack definitely needs balance charging for cells of different batch/ age.

I was planning on either removing the bad cell or using the pack as a 3 cell with the bad cell still in use. The way I see it right now is the bad cell really wont do any harm to the good cells because if anything the pack as a whole will reach LVC sooner and thus protect the still strong cells. I used a balance charger everytime I charge my packs so no damage there either. The only problem I see with using the bad cell is that it will further be damaged by repeatedly being over discharged when used.

Is that sound reasoning or is there something I am missing? I figure I will use it as a 3 cell a couple more times until the cell burst and then toss it out.