Tim,
I flew my Excitation at the King Orange in 40F temperature. All I did was add a wrap the exposed edges of the battery with a thin strip of bubble wrap. I carry my batteries in an Army surplus ammo case that I added separators to hold 6 - 4S1P 3900 batteries.  If you put the ammo case in the sun it will keep the batteries toasty warm and ready to use. If you have real cold temps you can add a hand warmer pack inside the ammo case to add some additional heat.

Best,                DennisT

Go flying, and check the temperature as soon as you land.  Your question will be answered.

If the battery is cold after a flight, and if you can block the airflow to the battery without interfering with the ESC cooling, do so.  Then check again, to make sure you didn't go overboard.

Remember that warm things feel lots warmer than they really are when your hands are freezing.

Thanks Tim and Rudy,

You answered my questions, this Saturday looks promising weather wise, looking forward to getting out and do some testing of the T33.

I will let you know how it goes

Tim

Just what happens to LiPo batteries in the cold?  If their capacity is reduced, I suppose one could reduce their life by discharging them too much, particularly when the energy required per flight increases with air density, too.  Overdischarging might warrent an annunciator (so you won't get caught in an overhead eight) and an early turnoff feature.  Just slowing down a little in the clover may not be a big deal. 
 

Maybe a workable alternative to selecting a battery of the proper size to compensate for the cold temperature is to simply dial your timer back to a shorter time limit. Setting the timer to say 5 minutes (or an appropriate time) instead of 6 minutes (or your usual interval) and using your regular batteries should give the safe overhead needed. I know, maybe you cannot fly the entire pattern in a shortened time but, if you are not in a competition and just want to practice, does it matter all that much??

Cheaper and easier to reset the timer than to buy a bunch of new "cold weather" batteries. 

Rudy,

No shots with Ski's but I did fly this weekend with mixed results. Keep in mind that I am using Turnigy battery's that I have been using all season. They made out just fine all through the summer and fall but here were my observations:

Temperature: low 40's

3 packs 4S 3600 mAh all at a cozy 70 degrees in a cooler until ready to fly.
Timer set for 1.5 minute test flights, I have some bugs to work out, this plane has a lot of side area to deal with, and trim for
1. First flight lap time of 5.4
2. second flight same pack 5.8
3. Third flight on same pack 6.4

As you can see the pack did suffer quite a bit, but again, this is a well used Turnigy pack so I am really not sure what kind of conclusion you can draw. Old cheap pack.....or yes the cold is a factor.

The results were similar for the other packs as well. I can tell you that these packs have worked well in the warmer weather, but they did have issues last weekend.

I did try a 5S pack and had great power, I may have to switch to a 5S for this plane, much more dragging out in the wind over my tsunami. With the 4S Packs I have my RPM's maxed out on my Hubin timer to get the thing to fly 5.4 laps with the 13-4.5 and I really want to stay with this prop

Hi Tim,

Thanks for the report. Maybe we will get to see ski photos in Feb., when the snow gets really deep? 

I agree that we have to be careful in drawing too many conclusions from your results, because of the many variables.

1. As you said, one issue is that the batteries may be near their "end of life" stage (which in the battery world is universally understood to be when the battery will only recharge to 80% of it's original capacity).

2. The other issue is the one William eluded too: the lack of headroom did not give you anything left over to make up for the cooling of the battery.

3. The fact that they are inexpensive batteries may or may not be a factor. If you put a lot of flights on each of these (>50) then this may be an age issue.

I fly mostly ERC, and at our E field many sport flyers use the batteries you are using. They are so inexpensive that even though they always have a shorter lifespan than our ThunderPower, and Hyperion batteries, they still may end up costing a little less because you can buy 2 or 3 of them  as they wear out. This ratio is changing as our prices are coming down. But even so, I feel much better knowing that my batteries are putting out full power, at the C rating on the label and I can depend on them not failing at the top of the clover, or in ERC3D. ...... The inexpensive batteries still seem to work OK for many of the sport flyers. They don't stress them, and when they fail (some in 10 flights some in >50) it almost never is a problem, in sport ERC they can almost always land safely with full control. Not so in E-CLPA!   

4. With the above said, it looks like the cold had an impact! I agree that using the larger 5S packs is a good solution to make up for the power loss due to cold.

5. I'm glad you mentioned the greater amount of drag that our profile models produce. I notice it with my E-P-40. I hope more people realize that they have to have more battery mAh than with a similar size full fuse. plane.

6. There are a number of ways to solve this puzzle:
    1. Bring your plane and these batteries out here and fly it. It was 76 f yesterday. You can leave any skis at home. This will give us firm scientific data for comparison! 
    2. Get some 4,000 mAh batteries (same brand) and fly them to see if it was an "overhead" issue.
    3. Use some new fresh batteries, same brand. Then use some TP/Hy batteries.
    4. You could try an APC 13 x 6.5 prop. This will give you faster lap times, probably heat up your battery (pulling more Watts). If you try this, you may want to plan on a   possible short flight. ?

I like #1 the best. 

Thanks again for your experiment and data. It will be interesting to see how others make out in cold WX E-flying this winter. And thank you for bringing us so many beautiful E-CLPA planes. You are an inspiration to us all! 

Regards,     

I did try a 5S pack and had great power, I may have to switch to a 5S for this plane, much more dragging out in the wind over my tsunami. With the 4S Packs I have my RPM's maxed out on my Hubin timer to get the thing to fly 5.4 laps with the 13-4.5 and I really want to stay with this prop

Hi Tim,
All you have to do is twist another 1/2 inch of pitch into that prop, reduce the RPM to maintain lap time, and you have 10% more voltage overhead.
Are you using too high a percentage of the battery capacity to finish a flight, or are you running out of voltage even though you are only using 60 or 70% of the capacity.
If the latter is the case, then the added pitch fixes all.

Hope that helps,
Dean P.