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450 Class Electric Helicopters 450 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 01-25-2009, 09:29 AM   #1 (permalink)
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Default storage of lipo battery ??? at full charge

lipo storage in freezer at full charge ??? or keep in room temperature at what % of charge
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Old 01-25-2009, 09:51 AM   #2 (permalink)
 

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The two factors for LiPo storage are charge level and temperature. Long term storage of LiPo's yields the least reduction in capacity at lower charge levels. 40% charge level is a good target as it provides plenty of buffer to prevent over-discharge during storage. Lower than that and you risk permanently damaging the battery from over-discharge. No matter what the charge level is, lower temperatures reduce degradation during storage, but much less so when not fully charged. The ideal storage conditions would then be 40% capacity at ~ 0 degrees C. Typical degradation is ~2% per year in these conditions. However, consider that storage at 40% capacity at room temp typically yields only ~4% degradation. If you discharge to 40% capacity, It might not be worth too much effort to store them that cold. If you store them fully charged, then storing them at 0 degrees C will dramatically reduce degradation from ~20% per year to ~6%.

Keep in mind that these degradation numbers are for storage over a one year period. I don't know if the degradation is purely linear with time, but for short term storage of a week or so, you aren't looking at much degradation. The problem is that we are almost always "storing" because the window of use is so small. Then the question really becomes recharge right after use, or right before use. Ideally, you should charge right before using.
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Old 01-25-2009, 10:03 AM   #3 (permalink)
 
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Lipo Aging is a function of Temperature and Charge Level....

Chart for lithium polymer batteries in general and not an actual representation of a typical 3s for example and should not be used as such
Chart (aging): http://w00d.servebeer.com/lipo_aging.gif
As to benefits personally I think there's far too much brain power and over thinking going into this question of storage temps. I mean at the end of the day what would this translate into at the end of days for a typical Lipo 2, 4, 6 extra cycles out what 100, 200? For me 50% at room temp long term, charge just before I fly, within a couple of days if I must keep at 100% capacity, then bring back to 50% if I decide not to fly..
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Old 01-25-2009, 10:14 AM   #4 (permalink)
 

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Lipo Aging is a function of Temperature and Charge Level....

Chart for lithium polymer batteries in general and not an actual representation of a typical 3s for example and should not be used as such



As to benifits personaly I think theres far too much brain power over thinking going into this question of storage temps. I mean at the end of the day what would this translate into 2, 4, 10 extra cycles out what 100, 200?
By the way, that chart is for "permanent capacity loss". Consider that if you always charge your batteries after use, you are always essentially storing them at 100%, so you will lose 20% of your capacity over one year. So, if you plan on exhausting your batteries over a shorter period, maybe it doesn't really matter.
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Old 01-25-2009, 10:17 AM   #5 (permalink)
 
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By the way, that chart is for "permanent capacity loss". Consider that if you always charge your batteries after use, you are always essentially storing them at 100%, so you will lose 20% of your capacity over one year. So, if you plan on exhausting your batteries over a shorter period, maybe it doesn't really matter.
I was editing my post when you posted yours but I think I just said that or something similar LOL and apparently so where you...
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Old 01-25-2009, 10:26 AM   #6 (permalink)
 

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Yep, I think we are on the same page, here. I have a bunch of LiPo's so I hope to make them last more than one year. The data that I collected has made me change my ways with regard to when I charge. I generally don't let them get very low, so I just let them sit at room temp between charges, and try to charge as close to when I plan on using them. It is a pain, though, considering it's about an hour a pack to charge. It's also a pain to partially charge for storage, then finish before use. It's all a matter of how anal you are!
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Old 01-25-2009, 10:31 AM   #7 (permalink)
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lipo storage in freezer at full charge ??? or keep in room temperature at what % of charge
I keep all of my batteries 100% charged...I charge them right after I get back from flying since I don't know when my next opportunity will be.

I do keep them in the freezer when charged....it's what Kong Power recommends...check it:

http://www.kongpower.com/faq_en/show...xt01=&srhTxt02

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Old 01-25-2009, 10:41 AM   #8 (permalink)
 

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Skarn, that's a good suggestion; I have been considering that. Do you seal them in a bag to prevent condensation when you take them out? How long does it take them to get back to room temp? I tend to have little patience.
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Old 01-25-2009, 02:09 PM   #9 (permalink)
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Skarn, that's a good suggestion; I have been considering that. Do you seal them in a bag to prevent condensation when you take them out? How long does it take them to get back to room temp? I tend to have little patience.
First off I do want to say this: Even though I personally feel freezing is fine for ALL brands of lipo's, since only the Kong Power site specifically mentions that, for liability reasons, I would still recommend storing at 1/2 charge...But if they are fully charged, I feel it's fine.

Yes, I put my packs in a ziplock bag prior to putting in the freezer. But lately to be honest, it's cold enough here that I have been storing them in my garage...it's around freezing temp.

I've never timed how long they take to warm up....I pull them out about 1/2 hour before going to fly....and on the way to the field I carry the first ones I'm going to fly in my pockets....

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Old 01-25-2009, 04:32 PM   #10 (permalink)
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thanks for all your help
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