Need battery expertise

[Jason Church]

Hey there folks,

Just noticed that one of my batteries is starting to look like its getting a tiny bit puffy, I know that there have been quite a few upset people about this subject but all that I would like to know is when it starts to become unsafe flying with this battery.

Its a 5200/11.1V Visions 2 Plus smart battery and I have 26 flights with it, I have cycled it once after it's 20th charge to 8% and pay attention to the voltage numbers of the battery in the PC assistant every 3-4 times after charging, what are safe numbers of each cell and what would be unsafe numbers where I would no longer use it to fly and recycle it at my local depot.

Thanks for your expertise in the matter.

Jason

 

[Panamon Creel]

hmmmm what is a tiny bit puffy? Could it be that the cardboard wrap is just bulged a bit?
Generally speaking cell voltages above 4.2V should be avoided since it would reduce battery life.
Under load cell voltages should not drop below 3.0-3.2V, no load or minimal load not below 2.8V otherwise cells may get damaged
Cell voltages at below 2.5V load or no load are resulting in permanent damage ( some say they can be recovered ) and can cause the LiPo to self ignite.

 

[Jason Church]

Ok guys thanks for your info. It is much appreciated, I'll prolly recycle it.

 

[slothead]

hmmmm what is a tiny bit puffy? Could it be that the cardboard wrap is just bulged a bit?
Generally speaking cell voltages above 4.2V should be avoided since it would reduce battery life.
Under load cell voltages should not drop below 3.0-3.2V, no load or minimal load not below 2.8V otherwise cells may get damaged
Cell voltages at below 2.5V load or no load are resulting in permanent damage ( some say they can be recovered ) and can cause the LiPo to self ignite.

I agree with your question of semantics. What IS "puffy?" If the voltage specification that Panamon Creel suggests works, then ignore the puffiness altogether, but that may not work in all cases. What I would recommend (although it will still be somewhat nebulous) as an additional measure of degradation is to take a measurement of a good battery thickness and then one of a recently failed (and really "puffy") battery thickness and note the difference. Cut the difference in half, include some safety margin and then show this as a "puffiness" specification for use restriction. Obviously this will requires some experimentation and ideally someone (or DJI) with a failed/expanded battery for the worst case condition measurement.

The more I think about this however, I see a variety of levels of risk coming out of all this. Maybe we just need a safer battery technology or a better cell containment mechanism.