Low voltage lipo, how to charge.

[martin collins 1]

I left a 3s 2200 lipo connected in my plane which has an isolator switch, the switch was in the off position but 24 hours later the lipo is dead. Obviously can`t trust the switch but is it possible to charge the lipo up again? When i connect to my charger it just beeps low voltage and wont charge it..............

[gangster]

Try to gently bring the Lipo back up suggest switching the charger to nimh and charge a low current for a few minutes Then try to charge as normal

[PatMc]

Martin, the ESC will draw current all the time it is plugged into the battery whether the connection to the Rx is via a switch or is direct.

There is a method to sometimes be able to re-charge the battery, it isn't always successful & the battery will have permanently lost it's full capacity & ability to provide the same current output as previously.
To be honest as it does involve an element of fire risk, which I don't think is worth taking against the relatively low cost of a new battery, my advice is to put this down to experience & buy a new lipo.

[Ben B]

Don't bother. Even if it was an expensive battery I wouldn't bother. I've tried resurrecting discharged lipos and it doesn't work- sometimes some of the cells will wake up but the chance of all is slim and those that do will have IR issues. So even an expensive battery I wouldn't bother. On a 3s 2200? No chance.

Even if it appears to work when it burns down a plane / garage / house it's kind of an expensive way of saving money.

[Trevor Crook]

3s 2200 LiPos are £8.50 from Hobbyking - not worth a dodgy resurrection attempt.

Puzzled by your "isolation" switch. If I fit an isolation device, it's a high current connector link in one of the wires from the battery to the esc/regulator. If the link is unplugged, it's the same as having the battery disconnected, no drain possible from anywhere.

I must confess I only bother doing this now if the lipo connector is in an inaccessible place, or close to the prop arc.

[Nigel R]

"24 hours later the lipo is dead. Obviously can`t trust the switch but is it possible to charge the lipo up again? "

Exactly how dead is "dead"?

Sub 3V per call, is when damage really starts mounting inside the cells. More time, more damage. Lower voltage, more damage. It's a sliding scale. If it has been low "ish" for "not that long" then you might well still have a serviceable pack.

As for recharging, stick the charger in a different mode as gangster suggests. Give it something like 30 mins at 0,5Amp. Check how warm it gets. If it is ok, put it on a normal charge cycle.

Safety first hat on - do this all outdoors. Just in case.

[martin collins 1]

No reading at all on a voltage checker, i think it is an ex battery 😕

[Bruce Collinson]

Got one back last weekend, same 3S 2200, been in the flight box too long. Put on a low-ish NiMH charge, constant checking for heat, when it got back above about 10v I switched to LiPo balance and it charged satisfactorily, no heat, no magic smoke. Below that v the charger wouldn't have any of it, shouting low voltage.

Will be keeping a close eye on it all the same.

BTC

[Chris Walby]

Had a few over the years go below 10% and a couple that needed rescuing, done what has been suggested and all of them have never performed very well for very long.

IMHO the higher the discharge the more likely they are to fail on a rescue battery + I had one vent on me so in my book its not worth the risk. Bit of a gutter when its a 6S4500 pack with only a few flights and the flight time for the edf was 3m20s as it wasn't cheap.

Less of a problem with glow fuel as its universal to all of the engines I use never gets a chance to go off

[Martin Harris - Moderator]

I had a 6S pack die on one cell in an EDF - it's been doing sterling service reconfigured to 5S for my high voltage starter for the last 7 years...