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Old Dec 29, 2007, 07:25 PM
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Quantiatively how much does cold affect a lipo?

I know that a cold lipo will not perform as well as a warm one, so its capacity will in effect be reduced, but to what extent? I had two flights today under exactly the same conditions, the only diff between that for one my lip started at 55-60F and the second it was closer to freezing and it appeared that the same power requests from my plane reduced the lipo by at least 50% more in the second case (as such, upon putting it on the charger I realized I was probably 30 seconds short of running out of all capacity!).

I will be sure to not leave a lipo in the trunk for an hour again!
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Old Dec 29, 2007, 08:13 PM
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I have a similar story. My wife runs a school and I went there to fly. We went out to eat and I left my radio, heli, and batteries in my van. I came back and hour later and none ofmy batteries were flyable. Now I keep them in an aluminum camera case with my radio and make sure I keep it with me so it stays warm.
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Old Dec 30, 2007, 06:07 AM
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At around 20 F, if I take my plane out of the clubhouse, it will run for 5 mins. then power cuts enough to make it unflyable. Same batt will run for 10 mins. plus in summer time. This is with the batt. velcroed to the side of the fuse where it's completely exposed. I use a foam sock for the batt. in which it can generate enough heat to get the full run time.
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Old Dec 30, 2007, 06:24 AM
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Thanks for the responses--I'm glad that it is not indicative of a weakened bat and they truly are this terrible in the cold. If properly managed, though, it certainly avoids overheating issues
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Old Dec 30, 2007, 06:30 AM
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In fact, I run the next size bigger prop in the winter. A little more poop and helps keep the batt. warmer. I drive them a little harder in winter too. Not worried about driving them in as the snow makes a great matress.

Gord.
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Old Dec 30, 2007, 07:16 AM
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I usually put any batteries I"m not using, while flying, in my pocket. I'm not so sure that is a good idea...BUT....considering I live at over 8000' and the last few days it has been below -0, it works well for me!! I've been wondering what effect this low temp has on a glow engine...hmmm........I guess this is not the thread to discuss that though....CHEERS!!
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Old Dec 30, 2007, 08:07 AM
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I have found that around 40degf and lower lipo's drop off quick. Keep the car running and warm. Also keep the "next" pack to use in your pocket. A fully charged pack at 32deg will act as dead. Warm it up and it's good to go. Something to do with the chemistry for sure.
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Old Dec 30, 2007, 08:20 AM
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I just got back from flying this morning (28F). You do loose a slight bit of power but if you have a high powered setup anyway you really won’t notice much difference.
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Old Dec 30, 2007, 11:22 AM
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Quote:
Originally Posted by RC Man
I just got back from flying this morning (28F). You do loose a slight bit of power but if you have a high powered setup anyway you really won’t notice much difference.
I guess you kept the pack(s) warm until flight time?
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Old Dec 30, 2007, 11:29 AM
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http://www.rcgroups.com/forums/showp...75&postcount=1

Note:

Some have stated that charging LiPolys to greater than 4.0 volts per cell should be avoided at below 55F (?).

Not sure about temp. or voltage as I have read both 4.0 and 4.1 and 55F and 32F. Perhaps it depends on the phase of the moon.
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Old Dec 31, 2007, 06:19 AM
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Download this and read the last paragraph.

http://astroflight.com/store/pdffiles/123.pdf


Charles
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Old Dec 31, 2007, 06:35 AM
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Thanks, everyday. Given the military's increasing use of small backpack UAVs, I wonder how they address this problem in cold environments (though there isn't much cold about where most of them are being used right now).
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Old Dec 31, 2007, 08:23 AM
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Quote:
Originally Posted by JWilliams2
I guess you kept the pack(s) warm until flight time?
Yes they are charged and kept above 60F before flight.

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Old Dec 31, 2007, 08:27 AM
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Quote:
Originally Posted by JWilliams2
I know that a cold lipo will not perform as well as a warm one, so its capacity will in effect be reduced, but to what extent? I had two flights today under exactly the same conditions, the only diff between that for one my lip started at 55-60F and the second it was closer to freezing and it appeared that the same power requests from my plane reduced the lipo by at least 50% more in the second case (as such, upon putting it on the charger I realized I was probably 30 seconds short of running out of all capacity!).

I will be sure to not leave a lipo in the trunk for an hour again!
On the cooler days I have been keeping my packs in my pocket to warm them up, but I am a little leary of this practice. I am going to buy a heating pad and keep my packs on it, with a thermometer to keep tabs on them. We have the luxury of electricity at my flying club so power isn't an issue.

RCNXS
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Old Dec 31, 2007, 08:29 AM
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Quote:
Originally Posted by RC Man
I just got back from flying this morning (28F). You do loose a slight bit of power but if you have a high powered setup anyway you really won’t notice much difference.
This matches my experience. The coldest I have flown lithium packs is 32F and have not noticed a big reduction in power or duration. That's probably because they must warm up pretty quickly under load. They always come down just warm to the touch.
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