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Old 02-08-2011, 12:57 AM   #32 (permalink)
jperkosk
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Quote:
Originally Posted by redbird300 View Post
BTW Jerry, almost all my packs start puffing near the end of their lifecycle, no matter what brand. So I guess what's mentioned above could make sense ?
Yes it rings true. I'm not enough of a chemist to confirm or contradict any of this, but it all refers to normal life-cycle deterioration, it says nothing of permanent negative effects of storing the battery fully charged. Your experience seems to confirm this. Basically, Lipos will deteriorate at the end of the life-cycle no matter what and they will puff.

Quote:
Originally Posted by sutty View Post
Not sure if the jury is still out on this or not Jerry, everything I had read to this point had been that it is detrimental to keep them fully charged, so I will use this approach from now on. I feel sure it isn't going to do them any harm.
My point Sut is that what I do know is that Lipos have a limited lifetime measured in charging cycles, and that in fact holds true no matter what battery type. There are chemical processes involved in charging-discharging that make the battery deteriorate over the time. So within normal use limits the Lipo will take maybe 500 80% charge-discharge cycle, or 1000 40% charge-discharge cycles before it has deteriorated, right?

So my feeling is that deliberately discharging your Lipo to 50% is taking away a half charge-discharge cycle out of its lifetime, and I haven't found (or experienced) any evidence that storing them @ 100% actually harms them.

My current thinking based on what I found so far:
  1. If you expose charged Lipos to heat the self-discharge rate goes way up really quick, to the point that it can get dangerous to the battery's health and in extreme cases, even to the surroundings. At lower voltage the discharge current will be less likely to damage the battery even if stored improperly.
  2. Because of polymer (read plastic) cell containers the batteries are way more susceptible to mechanical damage compared to metal encased batteries of most other types. Shipping/transporting them fully charged is a much bigger safety risk, there is much more energy that a damaged battery will release. I bet you everyone would be recommending a 0% storage level if it weren't for a known fact that the Lipo doesn't survive these discharge levels.
  3. So based on 1 & 2 above I think if you make sure you store your Lipos @ <25C (not a very difficult task), and treat them gently while handling (difficult in crash, though ) they will actually give you more flying time when stored (properly) @ 100%, and you can keep them ready-to-go as an extra benefit . The whole "storage level recommendation" smells a lot like a strictly safety related issue rather than something aimed at maximizing your battery lifetime. Nobody sued any manufacturer yet for getting 300 cycles rather than 500 out of their Lipos, did they? On the other hand, it the battery bursts in flames... You get the picture.
Now, this is strictly my opinion based on the absence of any valid evidence to the contrary, which may or may not be correct. I haven't done any scientifically valid trials to validate my opinion, and I take no responsibility if your battery bursts in flames because you followed my line of thinking rather than manufacturer's recommendation .

For my part, however, unless the real evidence emerges, I will store my batteries 100% charged, ready to fly on a moment's notice, making sure they sit in their metal box on a shelf where they'll never get hit by a direct sunlight far away from the edge so they can't accidentally be knocked down .

Does it make sense to anyone, or I'm completely out my mind here?
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Last edited by jperkosk; 02-08-2011 at 04:45 AM..
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