charging Li-On battery in winter - looking for heating element

I am using BAT-SAFE box when charging my ebike battery (Li-ion Panasonic 36V/15.6 Ah) in garage. Problem is that in winter there are cold days when outside temperature is below 14 degrees and garage is not well insulated - How to warm up battery in BAT-SAFE box in order to get at least 50F ? We don't have lot of snow during winter so winter rides and commuting is not problem (with proper winter clothing). I would like to use some kind of heating element with built-in thermostat but most of them is suitable for higher temperatures (e.g. 104F 10W heating element for tropical aquariums). Any ideas ?

btw I just finished Chernobyl miniseries on HBO and I promise I will be careful

What you need is a good thermostat. This one can go as low as 40f.
https://www.amazon.com/Century-Ther...8XBMVAN6XWV&psc=1&refRID=JPSPQBTFH8XBMVAN6XWV

Also, you might have better luck with a reptile heater instead of a fish tank heater. A reptile heater is a flat pad, where a fish tank heater is usually a tube. you can get more evenly distributed heating with the pad.

You can specify requirements for a thin flexible heater (dimensions, power, material, leads etc.) here: https://farnam-custom.com/custom/flexible-heaters
The tool allows you to add a thermostat and sensors.

Beer warmer! Used for homebrew, usual very low wattage but maybe a little more pricey than other options as most home brewers use aquarium heaters instead. The more popular temperature controllers are well worth a look though, Inkbird ITC-308 is the model I'm using and very happy with them, plug in heater (and/or fridge) set temperatures, stays reliably within 0.5 degrees C. Garden incubators may be another option, just a simple bulb or even a (calculated) long length of insulated copper wire, they all just turn electrical watts into heat so it's mostly down to getting even heat distribution.

Chromium wire used for vaping.
www.fasttech.com
V=I*R
V/I=R
V/R=I

P=V*I
P=I^2/R
P=V^2*I

Start off with a low wattage and go from there. Be sure insulate the bare chromium wire so it dont short nothing out. Then insulate the wire inside so the heat stays in. Be sure the battery aint working too hard while the pack is insulated.

I used a heated knee pad for a small battery pack I had, it worked well and gave a bit of padding to the battery.
The item is not longer available from the seller I purchased from but here is a similar item for sale.

https://www.ebay.com/itm/2X-12V-Motor-Car-DIY-Carbon-Fiber-Heated-Gloves-Warm-Mouse-Pads-for-Foot-Knees/264077126952?epid=11026829878&hash=item3d7c392d28:g:rlYAAOSw1dtcCh0q

martinw said:

I would like to use some kind of heating element with built-in thermostat but most of them is suitable for higher temperatures (e.g. 104F 10W heating element for tropical aquariums). Any ideas ?

Click to expand...

The smaller ones made for reptiles are usually 5--7 watts and usually go from 0-35C. They're even heat and waterproof. Cheap too, you can get em for about $20

eta: I'm not sure how accurate the smaller ones are. there's not so much a thermostat as a variable resistor in them.

Inside and dry, you can just use a heating pad from the drugstore. Set it on the lower setting, and perhaps put it on a timer as well. After all you don't need it hot all night, just warm by morning.

If the heating pad is too big, then a smaller size snake heater will be perfect. Just because the pad is 104 f, does not mean the whole area or the whole battery will get that hot. A dimmer light switch could dial it down if you really need it, but I think when its that cold, the heater will be fine.


Cheaper still, any kind of plywood box, then put a 100w incandescent light bulb in there. Then put the box over the battery enclosure at night. Again, timer will make it turn on only when you want it on.


Re Chernobyl, Attached garage to your house? My wife heard the fire before a smoke alarm would have gone off, and we barely got out alive.


Read the book Ablaze, for a better account of the meltdown. The movie series is very good, but its fictionalized.

Use warmers and controls designed for clothing. Perfect.