The parts I ordered at the end of December have finally arrived. I'm sure I could have sourced most of them locally, but the price of projects could have raised a lot. The most important was the 20-pack of 3032 lithium batteries (under 3€) and single lens sunglasses ... (these links open sellers page on new window, go see them. I'll wait here).
I'm sure someone clever reading this post may well guess what's I'm building, but if you'll comment this project, please don't spoil until I have the prototype made. I will then shoot a video of it, though I may need to find someone volunteering to be front of the camera :-)
According the feedback on sellers page, there can be some duds amongst those 3032 batteries. So I checked the voltages with a multimeter and they seem to varies between 3.1 to 3.4 volts. According the typical data sheet (pdf file) these voltage levels indicates these batteries are essentially new. The first voltage drop at the begin is really sharp and the nominal battery voltage is 3 volts.
During the use the battery voltage will keep relatively steady around 2.9V until at the end voltage sinks rapidly towards 2.0V which is the official cutoff voltage. So, these batteries are just perfect to use with low power microcontrollers without need of any voltage regulation. And with low enough static power drain, there's not even need to add any kind of power switch at the circuit.
--- And Back to Freezer part.. These photos are taken with my trusty old E-510 digital SLR with Zuiko 14-54 lens. That does not sound like worth mentioning, until I remind that lately we have been having temperatures between -20 to -29 Celsius (-4 to -20 Farenheit) and I spend 2 hours finding the right shots. These images are Straight-from-camera Jpegs, with no post processing (website does scaling).
First two pictures are from University campus area and the last one from city harbour.