[EMS Discuss] LiPo battery recovery

James Hukill EMAIL HIDDEN
Sat Jan 4 17:59:05 PST 2014


Well done!

Even better that you did not burn your house down. LOL
You fire history and all.  Wink

Sent from my iPhone

> On Jan 4, 2014, at 5:14 PM, Ben Hallert <EMAIL HIDDEN> wrote:
> 
> Just wanted to share a little thing I did that might help out.  One of my sons flies R/C and an unfortunate intersection of hubris and forestry left one of his planes stuck in a tree for a couple days.  The big-bad part of this wasn't the heroic steps it took to finally settle on a PVC arm-longerer to get it out, it was that the Lithium Polymer battery was deep-discharged enough that the charger wouldn't recognize it and try to charge it. 
> 
> Deep-discharge is a killer of these batteries because the chargers are too danged smart to try and do anything with them if one of the cells is below a certain voltage.  This is part of safety circuitry that's part of the R/C industry's aggressive 'don't burn down houses' strategy but can leave you without when you need to fly.  It's happened to us before (a plane was left 'on' long enough to damage a battery, and these packs are kinda expensive) so I wasn't looking forward to this.
> 
> I did some reading on the subject and learned about why the charger was rejecting the battery.  I thought about it and speculated that perhaps if I forced a little power in, it might get that rogue cell (or two) above the critical threshold the charger is looking for.  I learned further that this is risky so I did this with something between the battery and my body/hands/face.  CAUTION: Be very careful when trying anything like this, LiPo batteries are basically little bombs if mistreated badly enough.  
> 
> The battery is a 1300mah 2S 7.4v 20C LiPo, for reference.  I took a pair of mid-gauge power wires and ran them into the charge plug for the battery.  Placing the battery in my ad-hoc blast box, I too the other ends and touched them to a 9V battery (positive to positive, negative to negative of course).  I held them in-circuit for maybe 4-5 seconds then disconnected the mess and took the LiPo to the charger.  Plugged it in and...  success!  It began charging.
> 
> Once fully charged, we did some tests on it then took it flying.  It performed well, no measurable degradation in power.  
> 
> So if you kill a LiPo with deep discharge, it may be possible to bring it back to life but be careful.
> 
> - Ben
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