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Getting shorter flight times in the cold?

CrazyFastFlying

Well-known member
#1
Hi,

I was flying my new XK A1200 earlier today. I am suppose to be getting 20-25 minutes flight times but I got about a 8-10 minutes on a 2s 2000mah battery(the one that came with the plane) I was wondering if other people are getting shorter flight times in the cold or is there a problem with my battery. I also couldn't climb very well, I would have to be at full throttle to slowly climb. The plane is a glider and has pusher prop. Any thoughts?
 

quorneng

Well-known member
#5
CFF
It does depend on what you mean by cold. There is a difference between say 0 (freezing) and -20 Celsius. What level of 'cold' is giving you the problem?

There are two temperature related issues, rate of discharge and capacity. Both fall away as the temperature drops.
This raises another point. A Lipo charged at room temperature to maximum capacity and then allowed to cool down to freezing or below in effect becomes 'over charged' which is likely to harm the battery reducing both its maximum discharge rate and capacity permanently. :(
In a really cold environment it is important to keep a battery at the temperature it was charged at and to fly with it before it has time to cool down. In most applications it will keep itself warm when actually flying.

So if you are talking just a 'touch of frost' then a significant drop on both performance and duration does indicate your LiPo may be 'getting tired'. By far the easiest solution would be to buy a new battery and see how that performs. It never hurts to have a spare battery and the performance jump from a new one can be quite an eye opener. ;)
 

CrazyFastFlying

Well-known member
#7
CFF
It does depend on what you mean by cold. There is a difference between say 0 (freezing) and -20 Celsius. What level of 'cold' is giving you the problem?

There are two temperature related issues, rate of discharge and capacity. Both fall away as the temperature drops.
This raises another point. A Lipo charged at room temperature to maximum capacity and then allowed to cool down to freezing or below in effect becomes 'over charged' which is likely to harm the battery reducing both its maximum discharge rate and capacity permanently. :(
In a really cold environment it is important to keep a battery at the temperature it was charged at and to fly with it before it has time to cool down. In most applications it will keep itself warm when actually flying.

So if you are talking just a 'touch of frost' then a significant drop on both performance and duration does indicate your LiPo may be 'getting tired'. By far the easiest solution would be to buy a new battery and see how that performs. It never hurts to have a spare battery and the performance jump from a new one can be quite an eye opener. ;)
Hi,

Thank you for the reply! It was around 25 degrees F. I kept the battery warm until I started flying and it was still warm after the battery alarm went off. I was also having some voltage drop. I always set my battery alarms to go off at 3.5v per cell. When the alarm went off, I came in to land and when I checked the voltage it said 3.8 volts per cell. Is that normal?
 

Merv

Well-known member
#8
Yes, I get shorter flights in cold weather. I store my batteries in the warm, when I fly, I keep them warm. I put my batteries in a nail pouch and hang it around my neck, keeping the batteries under my coat until I put them in the plane. Even with warm batteries, my normal 10 minute flight times are reduced to 6 minutes, with cold batteries, flight time would be 3 minutes.
 

Merv

Well-known member
#9
When the alarm went off, I came in to land and when I checked the voltage it said 3.8 volts per cell. Is that normal?
Yes, what you are experiencing is called voltage sag. The voltage drop under load, it will get worse as your batteries age. You could set your alarm to go off a bit lower. I like to gives my batteries a chance to recover after a flight. I like to see 3.5-3.8/cell 10 minutes or so after flight.
 

CrazyFastFlying

Well-known member
#10
Yes, I get shorter flights in cold weather. I store my batteries in the warm, when I fly, I keep them warm. I put my batteries in a nail pouch and hang it around my neck, keeping the batteries under my coat until I put them in the plane. Even with warm batteries, my normal 10 minute flight times are reduced to 6 minutes, with cold batteries, flight time would be 3 minutes.
Yes, what you are experiencing is called voltage sag. The voltage drop under load, it will get worse as your batteries age. You could set your alarm to go off a bit lower. I like to gives my batteries a chance to recover after a flight. I like to see 3.5-3.8/cell 10 minutes or so after flight.
Thanks for the reply! I'm glad there is nothing wrong with the plane or battery!

Can I wreck batteries buy using them when they are cold?
 

PsyBorg

Wake up! Time to fly!
#11
I used to fly year round until I realized I was cutting battery life nearly in half flying in the cold. Now I dont fly if it is under 40 degrees F. You can manage the damage a bit by how you handle your packs. Its not so bad for air planes pulling far lower currents but it still effects them. Keeping batteries in your pockets or in a warm car helps but then they still go from warm to cold unevenly when you are putting them in your aircraft. Now the outer cells are far colder then the inner ones. That uneven temp changing is what does them in.

That imbalance changes the internal resistance and that damages the packs. It adds up over time and actually gets compounded in warmer weather where you are keeping the packs hotter during use enhancing the imbalanced internal resistance.

You can fly in cold weather just remember that little bit each flight will add up over time and you will start seeing variations in how the cells charge and discharge. I cut my batter purchases in half by not flying in under 40f temps but I pull far more current thru my packs which takes those fast heat changes to the extreme.
 

BATTLEAXE

Well-known member
#12
CFF
It does depend on what you mean by cold. There is a difference between say 0 (freezing) and -20 Celsius. What level of 'cold' is giving you the problem?

There are two temperature related issues, rate of discharge and capacity. Both fall away as the temperature drops.
This raises another point. A Lipo charged at room temperature to maximum capacity and then allowed to cool down to freezing or below in effect becomes 'over charged' which is likely to harm the battery reducing both its maximum discharge rate and capacity permanently. :(
In a really cold environment it is important to keep a battery at the temperature it was charged at and to fly with it before it has time to cool down. In most applications it will keep itself warm when actually flying.

So if you are talking just a 'touch of frost' then a significant drop on both performance and duration does indicate your LiPo may be 'getting tired'. By far the easiest solution would be to buy a new battery and see how that performs. It never hurts to have a spare battery and the performance jump from a new one can be quite an eye opener. ;)
I agree with @quorneng on this one, if you are getting less then half the flight time and power then what you are used to then it could be the battery is tired. I fly In around -5 Celsius and I notice a slight difference but not half. And I usually don't want to fly at any colder then -10C, just to cold for the fingers lol
 

Merv

Well-known member
#13
Can I wreck batteries buy using them when they are cold?
I have not noticed any damage to cold weather flying. I'm sure it's possible to wreck a pack in the cold, just like you can in the summer. I'll fly down to about 20F, it's my fingers that give out first. My packs come out of the plane warm, they feel good on cold fingers.

I usually get 3 years out of a pack, there is no doubt lose the punch as they age.