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Thread: How to fix a low voltage lipo battery!

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Old 06-07-2010, 01:19 PM   #1
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Exclamation How to fix a low voltage lipo battery!

This is a great money saver if you go through lipo's alot..

After a battery goes bad, you can save it. Connect the lipo to a car battery charger put the car charger on 40amp 12volt charge and give the lipo a few (4-6) quick hits. Plug the lipo back into the lipo charger and you should be ready to fully charge that lipo you thought was trash!
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Old 06-07-2010, 01:30 PM   #2
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Old 06-07-2010, 01:33 PM   #3
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Quote:
Originally Posted by Tobuster View Post
This is a great money saver if you go through lipo's alot..

After a battery goes bad, you can save it. Connect the lipo to a car battery charger put the car charger on 40amp 12volt charge and give the lipo a few (4-6) quick hits. Plug the lipo back into the lipo charger and you should be ready to fully charge that lipo you thought was trash!
The battery was not "bad" the voltage on one or all the cells was too low to allow a good Lipo charger to charge it do to a pre-selected voltage per cell. It is doing what it is supposed to do. However if the voltage has not gone low enough to actually damage the cells the voltage can be brought up above the limit and may be still usable.

I do not recomend doing this as it could cause fire, explosion or both if the cells are in fact damaged. That being said I have brought Lipos back up by applying a NiMh profile/type charge at 1/2C for 5 to 10 minutes. If your charger has a voltmeter built in or you have a VOM monitor the voltage. If it comes up to 3 to 3.2 volts turn off the charger and reset to a Lipo charge and charge normally. If the cells were not damaged the pack is now ok.

Once again I do not endorse doing this. And if you do it inside your even dumber than I am.

Last edited by bobt; 06-07-2010 at 01:52 PM.
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Old 06-07-2010, 01:44 PM   #4
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Yeah, I watched Tobuster do this...from about 25 feet away, LOL! But it did work. The one time I had a lipo with too low a voltage, I brought it up on the NIMH setting pretty much how bobt explained it.
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Old 06-07-2010, 01:46 PM   #5
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Quote:
Originally Posted by bobt View Post
The battery was not "bad" the voltage on one or all the cells was too low to allow a good Lipo charger to charge it do to a pre-selected voltage per cell. It is doing what it is supposed to do. However if the voltage has not gone low enough to actually damage the cells the voltage can be brought up above the limit and may be still usable.

I do not recomend doing this as it could cause fire, explosion or both it the cells are in fact damaged. That being said I have brought Lipos back up by applying a NiMh profile/type charge at 1/2C for 5 to 10 minutes. If your charger has a voltmeter built in or you have a VOM monitor the voltage. If it comes up to 3 to 3.2 volts turn off the charger and reset to a Lipo charge and charge normally. If the cells were not damaged the pack is now ok.

Once again I do not endorse doing this. And if you do it inside your even dumber than I am.
I have tried the nimh thing and it didn't work. I have fixed to lipo's already with my info, one was a cheap Turnigy for testing and the other was a $200 peak racing pack my buddy Bob let sit too long pluged in.
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Old 06-07-2010, 02:09 PM   #6
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I have a turnigy 4s with one bad cell, i was thinking about turning it into a 3s pack.

Know anyone who has done that? I kinda did what you were talking about, but the cell wouldn't ever charge above 3.6v and the other cells were peaked out at 4.2v already.

What do you think?
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Old 06-07-2010, 02:32 PM   #7
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nah, I don't know anyone who has made a 3s out of a 4s. Have you tried running the pack a few times to see if it will work itself back up to 4.2 each cell? you can also try charging it after a run at a low(0.5-1.0) charge.
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Old 06-07-2010, 05:03 PM   #8
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Quote:
Originally Posted by Ghostrider86 View Post
I have a turnigy 4s with one bad cell, i was thinking about turning it into a 3s pack.

Know anyone who has done that? I kinda did what you were talking about, but the cell wouldn't ever charge above 3.6v and the other cells were peaked out at 4.2v already.

What do you think?
haven't tried with a large RC pack but on the smaller ones its all good.
Hard pack or softpack?

biggest risk the the mechanical build of the pack... sometimes they're glued together too hard to separate without damaging the ally bag cells.
(they're just a bunch of bag cells soldered together at their output tabs)

If so i'd just live with the deadweight and shunt out the dead/dying cell.

When you've got the tabs exposed workout which cell is the target
then connect a low current drain to it (eg 1 brakelight bulb) until its 0V.
Then solder a shunt (=short) across that battery permanently
with a connection that will take the current, either a scrap of wire or
often there's enough wiggle room to get the tabs close enough to solder.

Then you'll have to reconfigure the balance tap - trace which line you've
nulled out above and remove that from the plug & snip it off at the tab.
Now 1 by 1 remove the other "downline" tap lines and hop them over by 1;
unless the dead cell was last in the chain then you've saved some work.


A dead shorted LiPO is inert... just don't unshort it & try charging.

(well okie so i've also tried that... all i've tried have stayed open circuit & won't pass current charge. But best not try anyways.)
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