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Dec 01, 2010, 09:37 PM
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Does cold weather affect Lipos?


2 part question.

1. Does cold weather reduce your flightimes?
2. Does cold weather degrade the life of your stored lipos?

Thanks! Dave
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Dec 01, 2010, 09:47 PM
Way to many airplanes!
Quote:
Originally Posted by hidaven
2 part question.

1. Does cold weather reduce your flightimes?
2. Does cold weather degrade the life of your stored lipos?

Thanks! Dave

1. Does cold weather reduce your flightimes?: YES. It's a good idea to protect the lipos with some insulation, and also fly wide open throttle all the time (generating heat inside the battery)

2. Does cold weather degrade the life of your stored lipos?: NO In fact, it is suggested that if you don't plan to use lipos for a long time, to put them in storage mode (about 3.8V to 3.9V per cells) and store them in a fridge. (storage voltage is more important than cold in my book, but both are a great idea).
Dec 01, 2010, 09:48 PM
Registered User
In my experience, no and no. Though I'm not sure what you're getting at with the second question.

All batteries have some internal resistance. This causes them to self-heat when they provide significant current. If the battery sits enclosed in the model, it will probably be warm during the flight -- and almost certainly much warmer than the outside air. I suppose there could be an issue on a profile plane where the battery is exposed to the air stream, but I haven't noticed it.
Dec 01, 2010, 11:22 PM
Registered User
I get lower flight times with my Slow Stick when it gets cold out (35F and lower). The battery hangs in the open right below the prop wash. Wrapping the lipo with a piece of foam helps a bit.
Dec 01, 2010, 11:48 PM
Registered User
Aerobatman's Avatar
Cold definitely effects Lipo performance. I've flown the same packs in summer, then in winter. Typically I see a 10-20% decrease in power when the pack is below 40 F. Keep the packs warm inside your coat close to your body and you can decrease the power loss. The ideal Lipo storage temperature according to Greg Covey is around freezing and at 3.8-3.9 v per cell like RealGambler said.
Dec 01, 2010, 11:57 PM
ground penetration specialist
Nathan Schmoekel's Avatar
10-20% is also what I've found in flight with mine. I tape over the air outlets in my full fuselage electrics below 40 degrees.

My hand launch gliders, because they don't heat the battery worried me for a while, but the runtimes seem pretty unaffected unless the temps get below 25...the voltage definitely drops faster then, but so does my desire to be outside, so that's no biggie.

A cold LiPo still beats a hot NiMh or NiCad hands down!! We have it pretty good in electric land compared to eight or ten years ago!!
Dec 02, 2010, 03:39 AM
Retired
Tony K's Avatar
In cold weather I keep my lipo's warm in the car sitting on the floorboard with the heater on until each one is used. Still need to reduce my flight times by 10-20%, but it's OK because it's so cold then I need to reduce my time outside by 10-20%.
Dec 02, 2010, 08:51 AM
A man with too many toys
1. I have found that if you keep LiPo’s warm before a flight and you restrict cooling airflow a little that they have close to the same performance and flight time. If you have a park flyer with low current draw and exposed batteries then time and performance will decrease as the battery cool.


2. Storing at half charge in the cold will actually preserve batteries. The only harm will come if you try to charge a very cold battery. Warm them to room temperature before charging.


.
Dec 02, 2010, 09:16 AM
Registered User
mexico's Avatar
Quote:
Originally Posted by RealGambler
...... and also fly wide open throttle all the time
I didn't see that one coming
Dec 02, 2010, 09:43 AM
Registered User
flypaper 2's Avatar
I use the next size bigger prop in the winter to load the batt and motor more and keep them warmer. A win, win situation, warmer batts and more poop.I also make these little foam baggies scotch taped together and closed with velcro and held to the side of the fuse with same on the profile jobbies.

Gord.
Dec 02, 2010, 09:50 AM
You sabotaged my plane.
eliworm's Avatar
I use an old tube sock filed with uncooked rice. Heat the rice filled sock in the micowave for about a minute. (NOT THE LIPO). I then put the rice bag in the bottom of a Colmen cooler, followed by an old towel with the Lipos on top. The towel keeps the lipos from direct contact with the rice bag. It keeps my batteries warm all morning and ready for use on those cold flying days. It also helps sore joints, muscles and cold hands.

Jim
Dec 02, 2010, 10:34 AM
globemaster
nicoyenny's Avatar
Yes, there is a noticeable difference in the performance of Lipos when it is really cold.
As everyone suggests, keeping them warm before flying will help a lot, and no, as Jim says, microwaving them is not a good idea, it could lead to the hot and fast loss of your house ...
Dec 02, 2010, 11:34 AM
Registered User
mexico's Avatar
Quote:
Originally Posted by flypaper 2
I use the next size bigger prop in the winter to load the batt and motor more and keep them warmer. A win, win situation, warmer batts and more poop.:
Gord.
Does that work? Seems counter-intuitive. Voltage sags under load when cold so increase the load? Doesn't that make the voltage sag even more and give worse performance? I thought you were going to say run a larger battery.
Dec 02, 2010, 11:49 AM
Registered User
flypaper 2's Avatar
I start out with them warm and making them work harder makes them generate more heat. After a flight they should come out at about body temp.

Gord.
Dec 02, 2010, 11:58 AM
Takka-Takka-Takka
leccyflyer's Avatar
Yes, cold weather affects lipos, like other batteries, you can expect power to be down, and therefore duration to be down. If your model is set up to direct cooling air over the lipos in the summer then it'll supercool them in the winter time, unless you make a change. What I do is to put aluminium tape over the inlet ducts that are there to provide that cooling air.

The Lipos themselves sit in a Liposack, with a couple of chemical handwarmers to keep the worst of the chill off. One of those will give about 30 minutes of decent heat and so four of them last about as long as I want to be out in the very low temperatures. On returning home the crystallised chemical handwarmers are warmed up in a pan of boiling water up and they then revert to their liquid state for the next time .


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