[EMS Discuss] LiPo battery recovery

Bob Miller EMAIL HIDDEN
Sat Jan 4 22:48:58 PST 2014


I've gotten lead acid car batteries to start charging by putting
another battery in parallel with the dead one.  The gets the voltage
high enough that the charger will start, and eventually both batteries
are charged.

Of course, lead acid isn't dangerous like LiPo. (-:

On Sat, Jan 4, 2014 at 5:59 PM, James Hukill <EMAIL HIDDEN> wrote:
> 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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-- 
Bob Miller                              K<bob>
                                        EMAIL HIDDEN


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