Originally Posted by BaconRaygun

It could be a bit degraded. I've done it before, and what worked for me was to charge it at a lower C rating ( I mean like .1-.5C) and then gently run it down to 3.7 per cell (don't go all out, just putt around or use a low amperage cycle mode on your charger) . Cycle them a few times and then ramp up to 1C charge and normal discharge, and be diligent with stopping when your timer rings (or cut a few minutes off for a few cycles). Then after a couple of those cycles, go back to normal. It should get it's pep back after that.

Of course, watch for puffing throughout those cycles.

Over-discharge just once like that may reduce life of the pack, but hard to say for sure by how much. It's kind of hit or miss, TBH. I have a 2s RX pack that I've been using in my air radio for about 10 years now and have discharged it to almost zero a couple of times. I know it's a low C RX pack, so that is a contributing factor, but this one pack seems to be really resilient. I had to cheat in order to revive this pack, though, as it was so low it would not register as a 2s LiPo when the charger does the pre-charge test. I've also had packs that I ran down to 3.3 and they puffed in under 10 cycles.