In the winter, it regularly gets down to below zero here. I need a light to work on clearing snow on a dark driveway. I’ve read that Li-Ion 18650 batteries are only a little bit better than regular NiMH rechargeables in terms of cold performance, and only CR123 non-rechargables are good for cold. I’d still like to go with 18650’s.
Since I’m using my light on high when clearing snow, I was wondering if there’s a good way to build a headlamp cozy on a light to help preserve the heat and keep the batteries from freezing? Since I need to wear the thing on my head, I think I’m looking at insulating it when it’s mounted on the headstrap. I don’t care if it looks ugly, but it does have to come on and off so I can use the headlamp regularly too.
Mine is a Skilhunt H04. Looks pretty much like any other right-angle headlamp.
Li ion batteries won’t freeze even below zero, 0C. Or did you mean 0F? I think 0F might get them closer to freezing. I think at –40C and –40F
If you keep the Skillhunt or extra batteries in your inside pockets until you turn in on, it will be cozy, once it gets going it will keep them warm,
If you are worried about windchill I would think some type of soft silicon would be safe to use even if the LED gets super hot. I think I would put a silicon tube around the headlamp, and make a hole, Sort of like a finger glove. Wool is also safe to use around hot metals, but I am not positive if the LED could or could not ignite it, in case it gets in the way of LED.
Windchill doesn’t affect non biological objects so no worries there. The only affect wind has on a metal object like a flashlight body is to help cool it back down to ambient air temp a little quicker, it will never get below actual air temperature.
Other than that point I agree with the above poster. I frequently wear my liion headlamps for literally hours on end of extended <0°F outings and notice exactly zero runtime issues vs warm temp use. I do keep spare cells deeper in my pack on subzero hunting trips to try to keep them a little warmer.
I have an ATV fitted with a battery built with lithium 18650 cells. In winter here it drops to –6 or 7 C most every night December through February. I dress up warm and use it 2 or 3 times a week. If I hop on and try to crank the engine when it is that cold it won’t crank well enough to start most of the time. However, if I turn on the headlight for 2 or 3 minutes before cranking it will start. I turn the lights on and they get brighter and brigter as the battery warms. The reason this works is that operating the headlight causes the cells to warm as they discharge and that is sufficient to warm the cells enough to enable them to put out higher amps.
I think that if you start your outside work with a warm battery/light and run it on high the discharge current from the cell may keep the cell warm enough to continue operating in the cold. I have not tried it but think it might work.
The ATV uses LiFePO4 cells in its battery but they have the same cold weather issues as the 3.6-3.7 volt lithium cells we use in our flashlights. Using the battery also warms it enough to allow safe charging at sub-freezing air temperatures.
You could probably try this out by storing the light and cell in the refrigerator freezer and trying it out.