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Old Nov 26, 2007, 05:46 PM
I'm ahead of Rob
dvlflyr14's Avatar
Tempe, AZ
Joined May 2005
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LiPo Cold Weather Performance

I understand that cold weather does not appreciably reduce the total capacity of a LiPo pack but it certainly has an impact on the voltage that can be delivered under load at a given point in time. I am looking to see if anybody has data, such as voltage vs. time graphs at various discharge rates (1C, 5C, 10C and 15C) at different temperatures (100F/40C, 75F/25C, 50F/10C and 32F/0C) for a LiPO Cell or one of the general sized packs (2S 1200, 3S 1200, 3S 2100, etc) that we use.

The reason I ask is because as we get into the colder months of the year we all notice that our LiPo's performance seems to fall off. People are running into LVCs, lack of zip in the plane or heli, etc.. It seems some of us are only getting 2/3s the performance or flight time that we had in the warmer months. I have spent a little time looking for this data on the web but no where have I been able to find it.

thx,

Dan
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Old Nov 26, 2007, 05:53 PM
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San Jose Ca / RSA flyer
Joined May 2003
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if U voltage stabilize them at their respective 2S or 3S , 7.4 or 12.6 levels, U should'nt have any problems

I use a VOLTAGE CLAMP for this purpose

my packs hold a charge indefinitely and PUT OUT when I need it
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Old Nov 26, 2007, 06:19 PM
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I suppose in southern california you have no idea what he is talking about...Anyway, when it is cold I notice that the initial power is down but once the pack warms up during the cycle the power comes back. I have not noticed any loss in duration though.
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Old Nov 26, 2007, 06:31 PM
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Pleasant Valley Modelport
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I have a Walkera 4 that has the battery on the bottom, exposed to the 25*F air I fly in. The batteries chill too much to deliver full capacity, and I read It can damage them the same as >100% discharge. I used some foam sheet from the Hobby Lobby the ladies shop at to make a battery case. Now they heat to about 80*F.
A graph I saw, maybe at FMA Direct or Kokam showed a 2100mah lipo is only able to deliver about 1600 mah at about 25*F.
Better look into it.

CH
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Old Nov 26, 2007, 07:47 PM
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Gilbert AZ
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AZ and cold weather. Where and when.
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Old Nov 26, 2007, 07:49 PM
Progress not Perfection
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Palmdale, Ca.
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Flagstaff in January
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Old Nov 26, 2007, 08:00 PM
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Gilbert AZ
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ok you got me there
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Old Nov 26, 2007, 08:03 PM
Progress not Perfection
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Anytime, (gotta love this site)
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Old Nov 27, 2007, 08:47 PM
Reduce the drama...
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USA, OR, Damascus
Joined Apr 2004
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Cold batteries!
My daughter complained her car started sluggishly.
Temperature has recently dropped into 30s.
Time to replace her car battery.

Cold weather may not affect the voltage,
but it will affect electrolyte ability to pass current.
This is true for all types of cells.
Leave your alkaline powered flashlight out in freezing weather, then try to use it.
Dismal.

The workaround for some is to keep the pack in an inside pocket of your jacket until ready to fly. Could also restrict airflow to pack when in fuselage.
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Old Nov 27, 2007, 10:28 PM
BEC
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Auburn, Washington USA
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I was flying my Stevens Aero SHAFT (review in progress) late Sunday afternoon in 45 degree air. The SHAFT has a pretty good battery ventilation system built in. As such, my flights were shorter before the LVC cut in than when flying at 15-20 degrees higher temperatures. The difference is only 10-15%, but if it were freezing out it would have been much more dramatic.

I was flying with an EagleTree logger and had ESC and motor temps that never got above 65 degrees. These were noticeably lower than the prior flights on a warmer day. I should put a sensor on the battery next time I go out and see what it does.

In general in the cool weather I recommend getting the battery out of the prop blast. Then its natural tendency to warm under discharge will keep it working pretty well once you start to fly. For this airplane I probably ought to block the air inlet on the nose when flying in the winter.....
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Old Nov 28, 2007, 06:40 AM
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BEC, I don't know what your LVC is set for, but you should average your flight time and try to land at 80% discharge. I use a Walmart timer to come back slightly under 80% discharge with 3.8v/cell average open terminal voltage. Seems to be working, I am over 150 flights on a battery people are saying dies at 50 cycles, a Megapower 2100 15C, and it seems as strong as new, and almost kicks as hard as a TP2100 with 90 cycles.

CH
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Old Nov 28, 2007, 08:29 AM
<- Balsa flies better ->
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Gustafs, Sweden
Joined Feb 2006
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Until you tried different conditions and different type of aircraft you're pretty much in the blue.

Winter flying with temperatures ranging between -5C/23F - -15C/5F takes a lot of different measures to be possible. A lot of trial and error. Fly, measure motor and LiPo temperature until you get a "mental template" (or simply write it down ) for what's needed in a surtain model type.

The lower the amp draw the more difficult it gets as a high amp draw at "normal temperatures" usually involves special air intakes that you can plug when it gets cold. The batteries is kept in the pocket or in a friggo box until flight and the high amp draw will keep them warm during flight.

My experience is that trainers and thermal E-gliders are the most difficult ones to get a successful winter flying setup with, a friggo battery bay and a "pocket pal" usually does the trick.

Anyone who thinks 5 months of winter with snow is exotic can PM me for a "house swap", SE Asia/Australia or Florida preferred, kids and wife not included

Peter
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Old Nov 28, 2007, 09:08 AM
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I have been trying to find that graph, I am not severly schizo but it did state the reduction in capacity. I am finding conflicting statements about the situation so in order to settle my logical lobe, I am assuming the low discharge capacity is still there and you can draw 2000ma SLOWLY from a cold 2000ma battery. So that brings me to assume the chart implies that you get an EQUIVALENT reduction in useable high discharge capacity. That would serve as a flight time prediction tool.

CH
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Old Nov 28, 2007, 10:09 AM
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Beijing, China
Joined Nov 2006
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I'm pondering these same questions myself. Beijing gets well below freezing in winter.

Maybe going from 2 to 3 cell packs in winter might make up for lower performance?
what do you guys think?
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Old Nov 28, 2007, 10:48 AM
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This is from a battery manufacturers specs, "Lipo batteries will experience a 30% temporary decrease in capacity at temperatures below 32 deg. F. Flying in extreme cold weather should be done with great care. never expose them to temp. below -4 deg. F." and i have found this to be true when flying in idaho.
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