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One of my saddles Lipos emptied by mistake. Now: Balance problems

One of my saddles Lipos emptied by mistake. Now: Balance problems

Old 07-13-2014, 11:51 AM
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Default One of my saddles Lipos emptied by mistake. Now: Balance problems

I had two saddle-pack-batteries (5.0mAh total) for use in my Xray XB4. One of them got emptied to 0.4V by mistake. I read the forums that I could charge the battery up to 3.0V before starting to balance charge normally by using the NiMH battery charging option in my charger. And that worked.

However, after many races my batteries are still not 100% balanced. They always timeout at lipo saddle balance charging. One battery is 4.33V, and the other is 4.00V at the end. And the charger just gives up with a timeout.

Can I just use the NiMH option in my charger again and just charge the 4,00V to 4.33V as the other?
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Old 07-13-2014, 12:01 PM
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That lipo is just dead. .4 volts is ridiculous, and I'm surprised it works at all. Probably the best thing is just to toss it, as the cells seem to be and probably are damaged beyond anything that can be done.
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Old 07-13-2014, 01:24 PM
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yeah thanks. they seem to be working fine so it's rather strange that you claim its dead.

"Theorectiaclly during the first stage of charging a Lipo it is not really different than a conventional charger, but whe the lipo reaches it 4.2v limit the lipo charger switches to a constant voltage mode. Constantly adjusting the amount of current the lipo gets to keep the voltage at the 4.2v/cell." (Rc-monster forum)

So I charged the lipo to 4.2V now and the difference is now only 0,13 volts
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Old 07-13-2014, 01:40 PM
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I mean at .4 volts discharged the lipo cell has probably been damaged beyond help, and now it's just a matter of time before the cell dies completely. And the little quote you had doesn't apply to when the cell has been damaged, but instead when you have healthy cells. Even .13 volts is still to far off to really use safely. Any more than about .1 volts is to much, and even so it should be balanced the same.
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Old 07-13-2014, 01:45 PM
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I doubt charging the lipo in nimh is what you want to do. In Nimh it keeps amperage the same thought the charge cycle of the battery, so you are probably raising the voltage of the lipo battery, and then when you take it off the charger, the voltage is going to fall back into unbalanced territory as it doesn't have the "push" of amperage into the cell due to charging. Really nimh should only be used to bump voltage enough that the cell can be recognized as lipo, and should not be used for anything more than that, especially charging other than what I just said.
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Old 07-13-2014, 04:20 PM
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Most chargers balance @300mah so it isn't enough to balance that much voltage disparity.
Try to charge the affected saddle as a 1s pack. See how much it went through, then discharge to 3.2 and see how much it gave. Do the same to the other saddle and compare one to another. Remember each saddle is a 1s battery
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Old 07-13-2014, 06:24 PM
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Please be aware you are taking several unneeded risks. Trying to use a cell that doesn't appear to charge properly. Overcharging the other cell in the process, which at the very least reduces life.

And the riskiest, apparently trying to full charge a cell with nimh settings. All it takes is a touch of distraction and one has a youtube worthy runaway. Intense fire/sparks likely to start most anything in the general area on fire and toxic smoke.

No need to be paranoid about lipos, but it is wise to avoid these well known risks. Lipos like all batteries are disposable items to begin with and are available quite inexpensively if needed. It just isn't worth it in the big picture.
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