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. 

good example !!

[/quote]
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.

Regret to say VC ji, your Lipo might be beyond recovery. this phenomenon is exhibited only when its damaged too much.
normally with a 5V charger, the cell would spring back to at least 3V and will stay there for a couple of minutes so that we can shift it to normal lipo charger and continue charging to 1C.
and this being a TX lipo is risky to go down suddenly switching your TX off.

Ashok.P

v2 eagle - Perhaps, you are sadly right. I notice that my electronics engineer (Sandy) is on board at the moment. Let me tickle him.

Just being curious, are you connecting the Nokia charger to the battery or to the damaged cell?

Yes I know I'm an idiot and many will call me mad. But in the pursuit of personal knowledge I stripped a puffy 3 pack of it's outer coverings and with a hypodermic syringe stuck each cell and allowed the gas to escape. I used one hand to apply sufficient pressure on the cell to expel the gas and the other hand to hold a piece of adhesive tape with which to seal the cells as soon as the cell was it's usual skinny self. I did this to the 3 cells and then liberally covered them with wing tape and replaced the outer cover. That battery is now used on my workbench and is used for setting up quadcopters and planes, testing motors and many other small jobs. The battery is about 4 years old and it's been "fixed" for two of those years. One cell is slightly down compared to the other two but still delivers the power needed.

I have since repeated the operation on a number of other cells and they are used when setting up multicopters outdoors and never any more than in hover mode, 2 feet off the ground. I've never been one to take silly chances, some may think this was a silly chance, but it works and more importantly it's saved me money. I'm not a believer in throwing which works or can be modified to do something other than it's original task. None of my doctoring has rewarded me with a repeat puffer and only one battery has had to be scrapped (apart from connectors) as it had one cell which refused to play ball. From new it was a little iffy anyway.

Just one point with buying batteries. May I suggest people be wary of Mega sales, Sales of the Year etc. etc. etc. with some well known companies. I know for a fact they are a front for disposing of older batteries. We all know batteries have a certain shelf date and for any company selling batteries, to be caught with those with a Use By Date about to expire, it means lost dollars. What better way to dispose of them by getting people to pay more for them than their original cost. I've seen some hobbyists go mad at some sales and buy up big on batteries which were selling for around 20% off. It was some time after those sales that batteries seemed to dying somewhat prematurely. They still worked and mostly still charged OK, but the loss was more than just 20%, sometimes as much as 40 to 50%. Anyone who's been with one company in particular may have noticed one type of battery which has been in every sale and in every clear out offers. It's a very long battery which was once pushed as suitable for modification to build your own, something I'd never recommend. I do suggest these are avoided because I couldn't imagine any warehouse manager repeat buying on an item which doesn't sell.

As I said, this does happen and the general manager of a Chinese Hobby outlet told me it's common practice. To be honest it a logical thing to do, but I can't help but think it's a little underhanded. Then again, I';m funny like that :-)   Stu

Has anyone tried this? Seems incredible. What do the pundits say? Can I connect a fully charged Turnigy 2200 mAh aircraft battery to my, one cell discharged to 0V and reading at 7.8V, Tx 2650 battery and revive it?

This may help
http://flitetest.com/articles/Parallel_Charging_Your_LiPo_Batteries

Edit: unsolicited response from a non pundit!

@VC Sir, please check the dead cell is internally short or not, else the good lipo also will be damaged.

Edit: also the working cells should be damaged due to over current charging if the dead cell is internally short.(just think charging a 2s lipo charging with more than 40 apms current)

@akhilzid - How do I do that?

Please remember that you are about to advise an illiterate idiot who is probably older than your Dad. So keep your advice simple and idiot proof.

FYI when I tested it with a multimeter, each individual cell beeped.

dont need to test the other cells and the connection i mentioned below is only for dead cell.

first confirm that the cell voltage below 1 volt

if yes,
use continuity tester(or with multimeter with continuity tester mode)


check by swapping connection(means if you tested with positive multimeter with positive battery lead then check also with positive multimeter with negative battery lead)

I checked that too. With the multimeter leads reversed, it does not work/beep. Now what?

Cell voltage is probably zero on the damaged cell.

that means the cell is not internally short, and good to go charging,

but i still recommend try charging with any smart chargers(like imax B6) in NIMH/NICD mode to recover battery to be safe side.

I have a Greatplanes Triton charger and it refuses to charge the battery on NiMh / NiCad Mode.

try charging just the cell only, not the whole battery.

Ok. Will try that too.

I had a similar problem due to leaving a Lipo in my transmitter which I forgot to switch off. The battery was discharged well below 3 volts per cell (I can't recall the exact voltage) I used the NImH charge at a very low input (100mw) and it recovered all cells. I do recall it refused to take the charge initially but as soon as I dropped the amps setting to 100mw (.1) it managed to keep charging. I waited until each cell was showing over 3.4volts and then quickly changed the charger to standard Lipo settings and away it went. One battery restored.

I keep a record of all my batteries with purchase dates and anything which could affect it's use such as being dropped, degassed or restored. I take notes on a battery if it displays a particular cell as low volts. The battery I restored did show a small loss in it's fully charged voltage. Point 4 of a volt I can live with.

Should any battery suffer being dropped or over discharged I use them either on my workbench, setting up or in one of my boats.

Vc ji, do you run er 9x in your tx?