Field charging Lipos in the winter

[John C]

I would like to be able to continue field charging my Lipos in winter (say down to 5C) so that I can get more flights than my 4 batteries would allow. I have read that the charger should not charge the cells to more than 4.15V if the temperature is under 10C. Unfortunately my GT Power XDrive-6 charger only seems to have a setting of 4.2V.

Is there a way around this?

[Ben B]

If you charge them quick enough they become self-heating Not sure what the way round it is (personally I wouldn't bother), bear in my whatever you use as a power source (unless it's your car with the engine running) will have a significantly reduced capacity....

[John C]

I am considering making an insulated box for the batteries and putting a hotwater bottle in the bottom. Water at say 30 to 35C should be OK and might keep the batteries above 10C all day. I have a couple of 60mm thick polyisocyanurate cavity insulation boards in the garage which should be pretty good. The charger would be outside the box and the leads could pass over some sponge to form a draftproof cable entry point.

Any thoughts?

I think I will do a trial charge with a lipo and a hotwater bottle wrapped up in blankets and monitor the temperature carefully!

[John C]

Posted by Ben B on 05/11/2013 14:51:03:

If you charge them quick enough they become self-heating Not sure what the way round it is (personally I wouldn't bother), bear in my whatever you use as a power source (unless it's your car with the engine running) will have a significantly reduced capacity....

I have been using the car battery as the power source and it seems to cope with charging three 3300mAh Lipos without the voltage dropping to a damaging level. You are probably right that I am being over fussy with the batteries but I plan to get a larger model at some time with 5000 mAh 6S Lipos which are much more expensive and I would like not to damamge them if I can help it.

[Depron Daz]

I've just charged as normal. First charge at home the night before (or morning of flight) go to field and fly, and just charge as normal via the car battery. All batteries are kept in my flight box at the field, spent ones are placed to one side, or put directly on the charger. I always charge at 1 - 1.5c at any time of the year, never had any problems, and some of my 3s 2200's are 4 years old. I use 5s 4000's in my big Extra, and again, never had any problems in the winter just doing what I've always done.

[John C]

Posted by Depron Daz 393 on 06/11/2013 13:45:47:

I've just charged as normal. First charge at home the night before (or morning of flight) go to field and fly, and just charge as normal via the car battery. All batteries are kept in my flight box at the field, spent ones are placed to one side, or put directly on the charger. I always charge at 1 - 1.5c at any time of the year, never had any problems, and some of my 3s 2200's are 4 years old. I use 5s 4000's in my big Extra, and again, never had any problems in the winter just doing what I've always done.

Thanks. That is very helpful. Perhaps the problem with charging in the cold is if the charged battery is then taken into a warm place but if you use it the same day at the field this should not be a problem.

[Depron Daz]

I only recharge at the field if I know I'm going to use it again, if not it just stays up the "dead" end of the flight box. Not sure if it's just me, but I like to let a used battery rest for 5-10 minutes after use before the next charge. Does it matter? I really don't know. The batteries tend to still be warm even after resting, especially if they have been used hard in any of my 3D planes.

Edited By Depron Daz 393 on 07/11/2013 00:35:12

[Tim A]

Have experienced lack of power due to cold batteries this winter for the first time - voltage sagged on full power after take off - low battery warning went off on transmitter, then after 2-3 mins cruising on 1/2 throttle battery had warmed enough to deliver full power. Embarrasing though was my first attempt in a club aerobatic comp.

It wasn't the coldest day I have flown either but we had a couple of -5 degree frosts on the previous nights and the batteries are stored in the garage so they must have been thorougly chilled hence low output. Batteries do seem to take a long time to warm up from this state.

So I went and and brought a warming bag from HK works well you can set the temp up to 45' Even kept my meat pie warm for lunch. end result better performance on cold days and a hot lunch at the field!

[John C]

Posted by Kiwikanfli on 07/11/2013 07:25:33:

So I went and and brought a warming bag from HK works well you can set the temp up to 45' Even kept my meat pie warm for lunch. end result better performance on cold days and a hot lunch at the field!

Thanks! That is a great bag for only $16! See **LINK** "the inbuilt microprocessor offers a 7 step heater range from 25ºC ~ 45ºC". I would be able to run it off the hefty leisure battery I am thinking of buying for field charging.