Lipoly battery problems...
 

Hi,

I apologize if this has been covered, but I couldn't find the info I need during a search.

I have been having trouble with LiPoly battery failures. Numerous failures. They all cycle at their rated capacity or close, but when flying they go dead in about 30 seconds to perhaps 2 minutes. (They used to run 15 to 30 minutes in my applications.)

These batteries are various makes and sizes; most all in the 1200 to 2200 3 cell size. They go bad in a year or less with only perhaps 20 cycles or so on them. I use a good charger; an Accucycle Elite, have my ESC's set properly, don't overdraw the battery "C" rating, etc.

But my hobby room is not air conditioned and can easily get to 100 degrees every day during the summer. Is this causing my stored batteries to go bad? Should I keep all my batteries in the refrigerator??

Thanks in advance for any input on this problem,
AV8TOR

RE: Lipoly battery problems...
 

you mentioned that you cycle the batteries.... not needed...
but what do you discharge them to (volts?)

RE: Lipoly battery problems...
 

Yes, the refrigerator will help them.

Something doesn't quite add up though:

Capacity is directly related to flight time on any given setup. If the battery "cycles" at the rated capacity then the only way to shorten the TIME is to increase the current. Furthermore a 15-30 minute flight averages 2-4C , yet a 30 second to 2 minute flight is 30-120C. This doesn't add up.

RE: Lipoly battery problems...
 

Well, first off I only cycle them to check capacity and/or see if they are still functional. I know it is not necessary to cycle Lipos for their own "benefit".

Secondly, that's the weird thing, most of them will cycle test fine at the low amperage, (say less than 2 amps) of the charger/cycler. But when you put them into use, and start drawing some real amperage in flying, like say 10 x "C" or 20 amps for example, they fall flat in a very short time. I know the math doesn't make sense, but I figured something was happening to them that caused them to not be able to deliver their normal amperage under the higher amp loading of actually flying them in place of just cycle testing with low amperage.

I cycle down to 3 volts per cell to answer that question.

AV8TOR

RE: Lipoly battery problems...
 

They must still have the capacity , yet not be able to maintain a decent voltage under heavier load. It sounds as if their current capability has diminished (increased IR)

It would be neat to graph one of your tired packs along side a new one, I think you'd see the difference easily. Possibly in addition to cold storage a higher quality pack might be an answer too.

RE: Lipoly battery problems...
 

Yeah, that's the only thing I could guess at; increased internal resistance. It is a bummer to have packs with so little use go bad. Guess I go the refrigerator route...

Are the new "Nano Tech" Lipolys from Hobby City any good?

AV8TOR