Solar Lights for Sub-Zero Temperatures

November 2021 ยท 2 minute read

In cold climates solar lights are nice but typically short lived. Moisture corrodes their circits and once covered in snow the low charge levels will destroy the batteries. This is unfortunate because winter months can be the most enjoyable and with longer nights a little extra light, diffused through a sprinkling of snow is very pleasant.

The easy way to circumvent these issues is to rip the guts out of an existing unit, replace its battery with a cheap (3-4$ aliexpress) greencap 100F supercap and stick the whole thing in a glass jar. If your conditions are similiar to mine in Canada this will provide year round light for 5 years (and counting) without maintenence.

While this isn’t optimal since these supercaps are rated at 2.7v and most solar lights use a single AA battery solar light (1.5v) in my experence it still nets great results and I haven’t found the need to go after that remaining capacity.

In my case I enjoy building them from scratch using the cheap Q5252f IC’s so you can adjust the brightness and avoid throwing the store bought units housings out. I then put them in a glass jar with some silica to absorb any moisture and burry them half in the ground.

Its hard to say what will break first in one of these lights but the LED should last 50k hours and the supercap ~20k hours, so it’ll probably be the lid of the jar that finally fails.

Other uses

I have used this circuit indoors with a candle flicker LED (more pictures on IG) and it works reliabily even in dim rooms.

Also to fill a knot in my deck that lights up each night by casting the LED and circuit in resin with the solar panel under the board, protected from the elements.