While I probably live farther north than anyone else here (57' 08"), our climate is oceanic, not continental so we don't get extremes of temperature.
However, lots of people here do and since winter is coming in the northern hemisphere it is interesting to see what effect it has on the cells we use.
As a preliminary test I put a Romisen RC-C6 with an RCR123 in it into the freezer for a day then measured output (outside the freezer) compared to output at room temperature. The original discussion is to be found from here onwards.
The light is now at just under -22oC (-9oF) having been in the freezer for 20 hours. I've not yet figured out how to get good measurements in the freezer so I'll pull it out and do instantaneous, 30 second and 2 minute output measurements. Unfortunately I can't do these in the freezer but the light should still be pretty cold at 2 minutes. 229, 241 and 290 lux with an RCR123 which was fully charged for this test. It is not comfortable holding a light at -22 degrees.
Here's the comparison: Top row is lumens at -22oC, bottom row is lumens at room temperature.
Lumens | Lumens | Lumens | |
Temp | switch-on | 30 secs | 2 mins |
-22 | 41 | 43 | 52 |
+20 | 125 | 131 | 135 |
I'm probably going to have to build another lightbox to do more thorough testing, one small enough to fit in the freezer.
I don't have room-temperature numbers for CR123 cells in this light. Probably best to do room-temperature numbers then toss the light in the freezer for a day.
Once I've got a smaller box I'll do instrumented runtimes with different cells.
Any suggestions are welcome. I have a small cardboard box looked out and have ordered a small solar cell from DX though I'll look around locally since HK Post is running behind just now.
Then I can do the tests at -22oC which seems to be as low as the freezer wants to go just now.