Battery Voltage Drop at 25% InFlight

[FL_Kim]

Hello,
We've had a handful of instances where the battery voltage displayed on the controller drops at a consistent, "normal" rate until it gets to 25% then it drops very quickly. Can anyone please explain this behavior and how we may troubleshoot? Is the battery no good? We have many batteries and none have had excessive flight times.
Thanks,
Kim

 

[fpvsteve]

You mean the flight battery, right?
This indicates a bad cell in the battery pack if this happens repeatedly with the same battery.
There is no fix but to exchange it.
This can happen if you fly towards 0% capacity. One incident where cell voltage drops below 3-3.2V is sufficient to permanently damage a cell.
If this happens right away with a new pack it's likely a manufacturing issue.

 

[Pedals2Paddles]

I agree it means you have at least one bad cell in your battery (there are 4 cells in it FYI). And it is indeed not a condition you can repair. You should contact 3DR via support ticket and see if you can get a warranty replacement battery.

It's a little more complex than than getting near 0% though, and I don't want to see people get scared into landing at 20-30%... which I see a lot of here and on FB. In short, everyone should be watching the voltage in the app, not just the % remaining. Be on the ground with the motors off by no less than 13 volts. And remember it will begin dropping off very quickly after 13.8 volts.

 

[Scientific11]

I agree it means you have at least one bad cell in your battery (there are 4 cells in it FYI). And it is indeed not a condition you can repair. You should contact 3DR via support ticket and see if you can get a warranty replacement battery.

It's a little more complex than than getting near 0% though, and I don't want to see people get scared into landing at 20-30%... which I see a lot of here and on FB. In short, everyone should be watching the voltage in the app, not just the % remaining. Be on the ground with the motors off by no less than 13 volts. And remember it will begin dropping off very quickly after 13.8 volts.

I've notice my battery at 14 volts. But lately around 16 volts by the time I land. What does this mean

 

[RichWest]

For the sake of conversation and to a few topics covered about voltage drop at the low end of the battery. Would a full throttle event at sub 20% cause the voltage to go below the recommend safe volt point? If so, would that be a case to damage the battery?

fwiw, I'm a 20% land person. The distance I can travel via VLOS can be far. So full throttle back is not uncommon.

 

[Lon Snyder]

It's my understanding that Lipo batteries are well known to have a non-linear discharge rate


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[erikgraham]

It's my understanding that Lipo batteries are well known to have a non-linear discharge rate


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Exactly. I don't know about this bad cell theory. Everyone's battery falls off a cliff at 25%. That's just lipos.

Maybe the OP is aware of this and is talking about something more extreme?

 

[RichWest]

If you have a bad cell, I'd assume the discharge rate would be noticeable the entire battery. Can LiPo cell's be "kind of" bad?

 

[erikgraham]

If you have a bad cell, I'd assume the discharge rate would be noticeable the entire battery. Can LiPo cell's be "kind of" bad?

Yeah for sure. It's not a digital on/off thing. They get progressively worse as they are used because lithium oxide (Li20) builds up on the terminals internally.

 

[Pedals2Paddles]

For the sake of conversation and to a few topics covered about voltage drop at the low end of the battery. Would a full throttle event at sub 20% cause the voltage to go below the recommend safe volt point? If so, would that be a case to damage the battery?

fwiw, I'm a 20% land person. The distance I can travel via VLOS can be far. So full throttle back is not uncommon.

Yes. The voltage dropping below 3.0 to 3.2 volts per cell is harmful, whether it is under load or at rest. And of course, if the mission dictates landing at 20%, have at it. In your case, that final 20% may not really be practically usable fuel. But for most of the users, flying close the landing area, that would be sacrificing several minutes of flight unnecessarily.

 

[FL_Kim]

You mean the flight battery, right?
This indicates a bad cell in the battery pack if this happens repeatedly with the same battery.
There is no fix but to exchange it.
This can happen if you fly towards 0% capacity. One incident where cell voltage drops below 3-3.2V is sufficient to permanently damage a cell.
If this happens right away with a new pack it's likely a manufacturing issue.

Yes. The flight battery. Will test suspect battery again. We don't fly to 0% capacity. Thanks for your reply. -Kim