Hi, I overdischarged a slightly puffed 3 cell lipo while I was experimenting with my first quad The current after discharging was 10.5v . Is the lipo still usable?

Nope, it's unstable and non-usable.

Charge the particular cell at 4.5v dc only a minute or two!! If its back, well and good !!

The more time it passes after an over discharge of a cell, the more that cell becomes damaged.
Even if you are able to get the cell back, it won't be able to get fully charged and will show a great deal of voltage sagging.

I'm highly against such "Recovery methods" since continuing to use a LiPo with an unstable cell is simply calling for mishaps sooner or later.
It's best to discard the damaged cell (if not the whole LiPo) ASAP.

(Y) safety first!!

Thanks for the advice. Better to discard it.

@kiran rc,
If you still have the battery, please check and post the voltage of each cell.
10.5v does not tell you enough.
The cells could be at 3.5v each, or two could be at 3.75v and one at 3.0.
These two scenarios need different handling.

If it was me, I will definitely give a try, first of all do your charer detect it as a 3 cell LiPo?,
Which is your charger?
As Iyer sir said please post voltages of Individual cells, You can do that by measuring voltages through balance port.

The lipo cell goes bad if it is below 3v. If it is 10.5v then it does not mean that the cell is not usable and we need to discard.

Please measure the individual cell voltage as suggested above and charge it normally with a balanced charger. It will revive the battery.

Cheers
Asutosh

If Individual cell voltage dropped below 3v, balance chargers won't recognize that cell, so for again using it we have to boost that cell with external charger.

HP always ask to use Genuine Ink Cartridge but a good amount of people people refill it. 

You will use it or discard it, will depend entirely upon your options. I will recommend, try it. If it's 3 cell, use a 12 volt charger and charge it through a 100 watt 12 volt Car head lamp or any high wattage resistance till all cell attains at least 3.15 volt. Then remove the battery and connect through a balance charger.
After getting revived from deep-discharge condition, cool it using refrigerator for 12-24 hour. Then connect cell tester in balance charger port and use 100 watt 12 volt lamp for discharge measuring time and discharge upto 3.32 or 3.35 volt. Measure time calculate efficiency. If it is > 85%, you can use.

Keep in mind the golden rule of LiPO " Throw the LiPO cell if voltage drops below 2.7 volt". Else you can test it. However, keep the watch over battery temperature. If it remain cool, Go, use it. Give full throttle for little time and then again check heat. If no heat, NO PROBLEM. 

Quote from: KALYANPRODHAN on October 29, 2014, 12:56:14 AM
HP always ask to use Genuine Ink Cartridge but a good amount of people people refill it. 

good example !!

[/quote]

Quote from: KALYANPRODHAN on October 29, 2014, 12:56:14 AM
After getting revived from deep-discharge condition, cool it using refrigerator for 12-24 hour.

Why we should refrigerate a LiPo ?

It is a trick to overcome puffing. the internal foil shaped plates are kept in spiral like shape, and while cooling, it naturally press (Outer foil) the inner part which improves performance. I don't know more detail, but it worked.  Moreover, in a battery pack for Handycam (Sony TRV285) jumbo battery pack, found an iron block in between the cell just to pressurize them. I survived 2 LiPO from dead condition (Voltage gone 2.6 volt) In both cases the battery survived and no puffing occur.

You may laugh, but I survived data from a unreadable pendrive keeping for over a week in deep fridge. Sometime Shock therapy (Thermal) works when no other alternative is in hand. It was recommended by an friend in 2002-03 at yahoo electronics chatroom... but this can be done for lipo, read in somewhere in battery section for an china/japan based page translated by bablefish in yahoo search (surprisingly not google search) on 2012-13 and revived 2 battery successfully...

When the process don't need much extra investment, I recommend that to use... FUNNY na...

Yes really funny.......,
But as you succeeded, I will try too, Looks like extra work for already piled up old kenstar 

Thanks for all your replies. I have managed to get the voltage by charging.But it does not perform as well as it was before.

Turnigy 3S LiPo 2650 mAh Tx battery was left on overnight. It has discharged to 7.65V. On a HK 010 Power Analyser it is showing up as a 2S with 3.83/3.82/0.

Have tried charging it with a Nokia Cellphone charger rated at 5V/350mAh. After 2 hours, no swelling, no warmth, the third cell goes up to 0.62V and the battery voltage reads 8.27V. The Nokia charger gives a readout of 8.89V when tested with a multi meter.

I have another Samsung cellphone charger rated at 5V/700mAh which reads exactly 5V on a multimeter.

a) Do I continue with the Nokia and leave it on longer?
b) Do I give the Samsung charger a try?
c) I also have a Greatplanes Triton Battery charger. Any options here?

Sandy, thanks in advance!

Regards.

Charge with Nokia charger will take more time to get the cell back to normal voltage, your Samsung one will do the work fast, In both cases you have to monitor the cell voltage continuously...

Thanks, will give it a shot.

VC why are you charging the cell with 5 volts, individual cell voltage should not cross 4.2 volts and you need a single cell charge set to low capacity 1/10C more like trickle changer 1/30C until cell voltage reach at least 3.3 volts .

get yourself a USB single cell lipo charger having charge select range of 100mah to Max 500mah.

http://www.rhydolabz.com/index.php?main_page=product_info&products_id=830

this is a fixed 500mah one

http://www.sunrom.com/p/intelligent-li-ion-li-po-battery-charger-through-usb

use NIMH mode in any IMax B6 like charger to discharged cell will help to recover that cell, but dont exceed 0.5Amps Current and disconnect while voltage reaches 3.6 volts.

Thanks all. This is one heck of a tedious process and just as exciting as watching paint dry. 

Charge it for 30 mins and the voltage reads @ 0.8V for the damaged cell and 8.45 for the pack. Switch off the charger it goes back to 0.1V and 7.70V respectively.

@VC sir,
Watching paint dry IS exciting.
When you try to speed it up with a hot air gun and see bubbles...
Hell, as an old boat modeller you know all this, like mixing NC thinner in Enamel Paint to speed it up...
Moral for reviving dead lipos - as slow as possible. Rush it only if you want to see bubbles.
Regards.


Edit: Haha. Noticed that VC sir AND Saikat sir are watching this thread!

@VC sir, forgot to mention that first you can check continuity/resistance of that cell with multimeter if it less than 0.5v,
and the resistance is zero(or continuity shows shorted) then no way to recover that cell.