LiPo Battery Death

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tOD

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I seem to recall reading somewhere that if LiPo batteries, in this case 2 cell, are fully discharged that they can't be recharged again. I recovered 3 from a rocket that was lost for 6 days. All measured less than one volt when recovered. I tried putting them on my charger and the charging cycle won't start. I was able to successfully charge a couple of other batteries of the same capacity and brand, so I'm pretty sure it's not the charger. Anyone else have any experience with this?
 

Handeman

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Yes, I had the same issue. A 2 cell LiPo got too low hanging in a tree overnight and my charger actually gave an error when it was hooked to the low battery. It ended up in the recycle.
 

Winston

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Anyone else have any experience with this?
Yes, they are damaged when allowed to discharge below 3V per cell. They will reach that low level if simply allowed to sit and self-discharge for long periods.
 

ksaves2

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Dispose of the pack. They’re not like nicads or nimh cells that can sometimes be goosed back to life. Lower than 3.0V per cell and they’re a goner. Chargers will not attempt to recharge an over discharged pack. Sure diddling with settings to get the charger to send current could be stupidly done and the key word here is stupidly. Consider lipos expendable and after finding a long lost rocket that had lipos in it, replace the batteries period. The only time there is an exception to the rule is when using a device that has an auto cutoff feature.

For example, the Beeline GPS tracker has an auto cutoff voltage that can be set via software if desired. For instance, a single cell 3.7V lipo shouldn’t be allowed to be discharged below 3.0V. One could say set the cutoff to 3.2 or 3.3V. Now there still will be low level current being drawn in this standby state but if say one’s rocket is hanging in a tree and it takes a week or two to get at it, the battery might be o.k. In that case, no harm done connecting up to a charger. If the charger goes into a standard charge mode, the battery is likely fine. If the rocket is lost for months even with the auto cut-off the pack will eventually be over discharged. Think of auto cutoff as buying a bit of time for the battery. (Not all electronics have an auto cut off feature.)

Doesn’t hurt to connect an over discharged battery to a charger because if it’s bad, the charger won’t charge and will likely give some sort of an alarm sound.

There‘s two philosophies here especially if one is using a lipo in a tracker:

One is drain the thing to death as one wants as much time possible to get a fix. That might be desirable with an RDF tracker situation. The second is use the auto cutoff to buy time for a battery pack. That might be helpful with a GPS tracker where one might have a good fix on location but just can’t get at the rocket for awhile. Like the tree scenario I presented above.

Consider Lipos expendable and one should be fine. Don’t fret over lipos. If one thinks a battery is bad, dispose of it and get a new one. I’ve driven many lipos to death early in flying small micro R/C helicopters. Drain a 3.7V 750mah pack in 5 minutes and they really don’t have that long of a lifespan even when allowed to cool off between charges and allowing to “rest” before recharging. Happy charging. Kurt Savegnago
 

manixFan

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To echo Kurt’s words, there is a reason chargers are set to not charge a battery with voltage below a certain level. The batteries are physically damaged by over-discharge. Even if you could get it to recharge, it very likely will have diminished capacity. Not something to use with a rocket.


Tony
 

tOD

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Thanks everyone. I figured they were junk. I've got some other stuff to go to Best Buy to recycle. Into the bag they go.
 

ksaves2

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Thanks everyone. I figured they were junk. I've got some other stuff to go to Best Buy to recycle. Into the bag they go.
Great call!!!! :)
 

Rocketjunkie

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Here's some videos on recovering over discharged Lipo batteries.
**I have not tried these so you are on your own.**
 

manixFan

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To save everyone else the time, you basically choose a different battery type that does not have a minimum safe voltage and charge at the lowest possible rate. Then once you get above that voltage, you can switch back to LiPo charging. The cells are permanently damaged, and according the those clips, every hour the battery is discharged the damage accumulates. So days is not good. There is also increased risk of fire during recovery. You can somewhat estimate the amount of damage by measuring the internal resistance compared to a good cell, and the amount of energy required to recharge the battery back to 'full' compared to an undamaged battery.

To me it seems penny wise and pound foolish to risk a rocket on a battery that has known issues.


Tony
 

Rocket Outlaw

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there is definitely a chance to save it. The key thing here is that they were discharged SLOWLY.... Where you get 99% of lipo damage is if they are discharged at a higher amp draw, that's what truly kills them. Use a NiMh/NiCd charge setting and charge at the lowest possible (.1 amp or lower if possible) If it can get to over 7v, you should then be able to switch to a LiPo setting and charge it the rest of the way (again on the lowest charge setting available). BUT after that, cycle them a couple times and watch how much capacity is put back into the pack. If each time they are close to the same and rated capacity, the pack should resume its performance. ONLY do this if you are willing to watch the battery continuously!

On a side note, i only do this on my large 6000+ mAh 4s packs. as cheap as the small capacity 2s packs are, its best to just replace it and err to the side of caution.
 

cerving

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For $3-$5 each depending on the Hobby King special of the moment, it's not worth trying to "recover" one. If it was a 6C 7000 mAH R/C car pack, I could see it, but if it doesn't work you're not going to have something falling out of the sky either.
 

Flyfalcons

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I'm not saying I have tricked my Lipo charger into putting some mah into a fully discharged Lipo, so that it would then recognize a safe voltage to charge the pack again. But I'm not saying that I haven't, either.

However, in the case of the small Lipos we use for altimeters and GPSs, they are so inexpensive that it's probably best to replace them.
 

Rocketjunkie

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I'm not saying I have tricked my Lipo charger into putting some mah into a fully discharged Lipo, so that it would then recognize a safe voltage to charge the pack again. But I'm not saying that I haven't, either.

However, in the case of the small Lipos we use for altimeters and GPSs, they are so inexpensive that it's probably best to replace them.
I agree. For flight electronics where every gram counts, they can't be beat. For routine sport flying, I still use 9V alkaline batteries.
 

Flyfalcons

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All my new stuff gets the Lipo treatment now, and I need to un-lazy myself and convert my old stuff over. With a good charger, I know exactly how many mah my batteries go through in a flight, and popping the avbay open to charge them is more convenient and less expensive than making trips to the store to get packs of 9V batteries.
 
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