Why, when you over discharge a lipo...it kills it....is there any way of bringing it back?

Maybe, depends on the voltage left and whether its damaged. If its puffed and still growing, its done, its dangerous and needs to be outside somewhere it can't do any damage.

If it hasn't puffed, you can try charging it as a NiMh (you'll have to select the appropriate number of cells to make charger happy with the voltage it does have) at low rate like 0.2 - 0.5amps. Watch the voltage and let it charge till you've got it back over 3v/cell (6+v for a 2S) and then stop charge. It should now take a charge as a lipo - if at any time during either charge process, it starts to swell, stop charging immed and take it somewhere outside where it can't do any damage.

Even if it does successfully charge this way and charges as a lipo, you have damaged it internally and it may not perform as before.

Thanks for the info.....Ill give it a try, its just a receiver lipo....I left it plugged in.

I charged it with 300mA's for ten mins.....seem to be taking a charge now, guess time will tell.

Monitor the voltage - you want to get it up over the minimum voltage for lipo - I usually let it charge till I reach 6.1v for a 2S or 9.1V for a 3S.

Then switch to a lipo charge - it should charge once its back over the min voltage.

I have a 7.4 5000mah i left the switch on in my truggy. It drained it below the charge rate my charger said it could not charge it. About 4months later i couldnt remember what the charger said exactly so i hooked it up again an it charged no problem. It was almost like it drained all the way down to absolute zero and charged for the first time. It seems flawless

Glad it seems to have recovered, but there is some internal damage from over discharging like that. It might be subtle and hard to notice, but it is damaged.