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Topic: Bad LiPo lost one cell (Read 215 times) previous topic - next topic

rushimw

Nov 11, 2017, 07:20 am Last Edit: Nov 11, 2017, 07:27 am by rushimw
Hi guys,
  This is Rushi. Now I've encountered with another worse problem. This is my fucking fate, if something gets sort out another problem arises. Anyways, I've been working on above question. I think tuning PIDs will hopefully fix that.

Although my new issue is I think I might have damaged one of the cells of my 3s LiPo 2200mAh 12.6V battery. I checked with multimeter, 2 ports show 4.2V each and one which is damaged shows something in mV. So Ultimately I can only get 8.4V of power from that battery. I also observed battery has puffed up little bit.

1) can I still test with that power or simply should I go for new one?
2) Is there anyway that I can recover that one damaged cell? I read and watched online videos saying sometimes you have to discharge all the cells and charge it. Will this help sort out the issue?

I am middle of testing and this shit happened. BTW it is the same configuration, no changes. And about total weight, I calculated approximate it goes around 880 grams.

here is the pic of total weight extraction and another one showing one cell might have gone when I am charging.

P.S. Sorry for bad handwriting

vertigo72

If the cell reads millivolts, wow, then its absolutely and totally gone. No hope of reviving that. When a cell is discharged below 2.5 or 3V, most chargers will refuse to charge it. You can usually "revive" those cells by using a "smart" charger (4 button charger) and setting it to NiMH, and charge that way until you get above 3V, and then charge like a lipo again. If you do that, your cell will have been damaged, and you will have lost performance, but it may still be usable IF the discharge wasnt too extreme and IF it wasnt in this state for too long (think minutes, maybe hours, but not days). Ive "revived" batteries that where discharged to 1.5V per cell that way, but anything lower than that seems hopeless.

As for continuing to use it as a 2 cell pack; you probably can if you absolutely have to, but be very careful. Never charge it unattended and assume it can catch fire at any moment. lipo fires are no joke. Just get a new one, and dispose of this battery safely (fully discharge it in salt water or make some fire works by driving a nail through it in a place where its safe the thing to burn/smoke/explode).




rushimw

If the cell reads millivolts, wow, then its absolutely and totally gone. No hope of reviving that. When a cell is discharged below 2.5 or 3V, most chargers will refuse to charge it. You can usually "revive" those cells by using a "smart" charger (4 button charger) and setting it to NiMH, and charge that way until you get above 3V, and then charge like a lipo again. If you do that, your cell will have been damaged, and you will have lost performance, but it may still be usable IF the discharge wasnt too extreme and IF it wasnt in this state for too long (think minutes, maybe hours, but not days). Ive "revived" batteries that where discharged to 1.5V per cell that way, but anything lower than that seems hopeless.

As for continuing to use it as a 2 cell pack; you probably can if you absolutely have to, but be very careful. Never charge it unattended and assume it can catch fire at any moment. lipo fires are no joke. Just get a new one, and dispose of this battery safely (fully discharge it in salt water or make some fire works by driving a nail through it in a place where its safe the thing to burn/smoke/explode).




Thanks vertigo. I'll have to go for new one anyway. And it is puffy too like phone batteries do. In terms of buying new one, should I go for similar one or should I upgrade it? This one was too heavy. I am kinda thinking to use it for my transmitter Flysky FS CT6B.

vertigo72

Not sure why you think its too heavy. You should have at least 3-1 thrust to weight with that combo, thats plenty. The only way to decrease the battery weight is either going with a smaller capacity or you can win a little weight by using a lower C rating; but 2200mAH capacity isnt a whole lot for a ~1Kg quadcopter, and your motor/esc's will pull close to 60A at full throttle, so I would advice against a significantly lower C rating as well (60C means 60x2200mA=122A in theory. C ratings are always lies, in reality it may struggle to deliver 60A).

Southpark

So Ultimately I can only get 8.4V of power from that battery. I also observed battery has puffed up little bit.
Sounds damaged.... especially since you're getting well below the usual voltage.... and puffy battery. Time for a new one. Also helps to have spares.... and maybe need to have some kind of current monitoring or current limiting system to avoid drawing too much current from the battery.

When it comes to rc and batteries.... have spares on hand. And check on power handling specs to try cut down on issues. Sometimes the issues can be due to quality issues. Hard to say what happened right now.

rushimw

Sounds damaged.... especially since you're getting well below the usual voltage.... and puffy battery. Time for a new one. Also helps to have spares.... and maybe need to have some kind of current monitoring or current limiting system to avoid drawing too much current from the battery.

When it comes to rc and batteries.... have spares on hand. And check on power handling specs to try cut down on issues. Sometimes the issues can be due to quality issues. Hard to say what happened right now.
Does that mean I may have to add BECs for current limiting. May be you're right about drawing too much current. Coz it hikes up on 50% + throttle too making quad unstable even if pids are reasonable.

Thanks though.

vertigo72

Bec ? Current limiting?
A bec is just the word we use in RC for a 5V voltage regulator, to power the electronics ( Battery eliminating circuit, the battery its eliminating is the 5 or 6V ;) ) You need that anyway, although its usually integrated in the ESCs.

And you dont need to limit current. Thats the ESCs job. You need a battery thats capable of supplying at least as much current as the ESCs request. More is never a problem. Too weak a battery is a problem.

The instability can have a million reasons, but its not a "too good" battery.


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