RC Airplane World Forum

Hello everyone.

I want to be able to fly in the winter.
In terms of NiMh vs. LiPo: does one outperform the other in cold weather (below 0 celcius)?
To prolong battery life in the cold, is it safe to put a heat pack in the plane with the battery?

Thanks

Matt

I'm running all NiMh in my planes. Lipo in my heli.
Performance wise I don't know the details of how they compare in the cold.
I know you are not supposed to get a lipo wet. But they also are not supposed to have air touch them.
I'll explain as it was to me.
As you proly have read Lipos are violent little buggers if they get unhappy. oxygen and water are both to be avioded.
So they are sealed up air tight, and thus water tight. Poke a hole in the foil bag they live in and all bets are off though. Get ready for the 4th of July.
I know guys that use them in thier R/C scale 4x4s and drive them under water with the battery out in the open with no ill effects. In thier words "If it's air tight then it's water tight , right?"
Always at your own risk though when subjecting any battery or electronics to less than friendly conditions though.

Back to my experiance.
I've not flown the heli with ther lipo in the winter yet. It's small so I just stay indoors.

With my plane though, I have not had any trouble with flying it in the winter when the weather permits. (calm, dry, cold)
What I do is always try to be taking my battery off the charger before I go out to fly. This way it's warm.
I keep it in my pocket until the moment I put it in the plane just before flying.
This way it's still warm when it goes in.
I also have the luck of being able to basicly fly right out the front door at home but keeping a battery warm i the car on the way to the field should be no problem as well. Does not have to be hot, just warm.

It seems always after flying the battery is still warm when I take it out. Keeps itself warm under current draw.

So I wouldn't put a heat pack in the plane with it. May overheat things. But that's just my $.02.

Hello...

Thanks for your thoughts. Now that I think about it, that is what I do with my camera battery. I keep it in an inside pocket if I'm not using it so it is warm when I need it. I suppose it would have to be really really cold for that to not be sufficient. And if it is that cold, then maybe I shouldn't be outside. Although I do like to test my limits with the weather at times.
Yes, I have heard about LiPos being a bit of a fire hazard if not treated right. The stories have spooked me a bit.

Type in "lipo vs temp" in your browser and get multiple articles on the subject.

One particularly interesting is . . .
http://74.125.93.132/search?q=cache:79E ... en&ct=clnk

NOTE . . . The above URL gives the HTML version (no graphs or pics)

For the pics and graphs go here . . .
http://www.geocities.com/gbobs7/QEFI81.pdf.

All batteries have internal resistance and any current circulating in them in any direction (charge or discharge) creates energy in the form of heat.

W = R * I (squared)
W = watts
I = current in amperes

W = E * I
E = voltage in volts

If the current is doubled so is the E.
Twice the current doubles the E so it explains why the I has to be squared in the first formula above.

Some of us enjoy this hobby because of the many aspects of knowledge that it involves.

Take your full charged batteries from your home temp, put them in your vehicle with you. Drive to your flying site. You are comfortable ? ? ? so are the batteries.

Install them in the model and fly.
Their discharge generates enough internal heat to keep the batteries happy while flying.

Examples _ _ _
If the internal resistance of the battery is _ _ _
--- 0.10 ohms and the discharge is 20 amps, you have a 40 watts heater in the battery.
--- 0.02 ohms and the discharge is 35 amps, you have a 24.5 watts heater in the battery.

and so on, have fun.

KILOP

Thanks for the more detailed info KILOP!

Nice to know the how and why on stuff like this. Helps in future choices.

Yes, isn't this hobby great! Part toy, part tech.

Matt

As just a toy, like any other toys, we can get bored after a while.

As a tech, we cannot get bored as there is so much fascinating things that keep popping up.

We all start at the same point. It is the constant progress that keeps us addicted.

What a rewarding addiction it is and we can manage it at our leisure.

We must not forget also the wide spread this hobby has.

-- We can start with the toy _ _ _
-- Then do some modifications _ _ _
-- Perhaps some repair work _ _ _
-- This may lead to an Almost Ready to Fly (ARF) and install our own preference radio system and other details _ _ _
-- Build a kit ? _ _ _
-- Modify a kit _ _ _
-- Try our hand and imagination at a self design airplane _ _ _

YES . . . the sky is the limit and that is where we are going _ _ _

ARE WE NOT ? ? ?

Enjoy,

KILOP

Yes . . . the subject of this thread is "batteries in cold weather"

My last post is far away from the original subject on which I posted earlier.

Thread are like trees . . . they grow branches.

How nice is a tree that has only the main trunk ?

The branches and needles or leaves makes the tree look nice and appealing.

Thread diversions make a thread appealing and provide continuity and interesting appeal.

So _ _ _ by all means go fly in cold weaher and enjoy the cleaner atmosphere, less humidity, less polutants, less haze, better view of the model, better performance and cooling of the IC engine or motor.

The batteries will enjoy it as well and so will the ESCs and the motor or engine will run cooler.

Inhale deeply the cool or cold fresh air and enjoy.

KILOP

Hmmm...batteries and temperature.
Thanks for that link, it was a nice and descriptive test of LiPos. I'm getting the impressions that Lipos pack tons of power, but in doing so, are volatile. It sounds like you should be more careful using them in intense summer heat than winter cold.
Now I am starting to wonder what other problems temperature could cause. Cold air is more dense so it should give the plane more lift. But would the cold, say -15 Celsius or lower, make a foam plane more brittle?
Another branch of that tree I suppose.

Matt

A question perhaps out of the forum purpose.

Many things in nature have so called "critical" criteria.

I understand this forum is dedicated to help the newcomer which rightly or wrongly I define as the fellow(s) who are absolutely new to the hobby.

I think we should avoid discussing any more advanced subjects like any branch of the tree and stick to the main trunk.

Although I feel that it is too restrictive I believe that we should not depart from the main purpose.

Soon enough, the beginner progresses to more elaborate subjects than "what should be my first model? That is already so well treated in Pete's website and his new eBook.

I just do not know where the limitations are in diverting toward more advanced discussions. I also am of the opinion that if more advanced subjects are not touched than the progressing beginner will go somewhere else for finding solutions to the problems that are invariably encountered.

The problems that the beginner runs into are not much different than the problems of the more advanced flier. We are then talking to someone with less knowledge and to keep at the beginner's level we have to bring in discussions that advance the beginner's universe.

I do not know where to draw the line so I often remain silent or wait for someone else to post an initial reply.

Nor would I like to rectify what I may consider erroneous because it attracts resentment from whoever misunderstand something or emit (write) an unfounded opinion that is not based on experience or past known good application.

I honestly DO NOT know the brittleness characteristics of foam of any type (composition) versus temperature. I only have a feeling that cold temperature would not affect the foam to a point of making a model unusable in cold weather even below the freezing temp.

One of the local club nearby has a fun fly every first of January with a brave couple of dozens fliers tearing the cold air. Some electric and some glow fuel are participants. I only suspect that some models are foam.

KILOP