I recently witnessed how a 2,400 mAh 18650 was diminished to 300 mAh being stored for years in a vehicle. So, I decided to test out a vacuum seal insulated bottle with a batt. loaded NiteFox UT20 in it. The light was wrapped in a microfiber cloth. The test subject was a new $6 Ozark Trail 24 oz. bottle that I'm not planning to drink out of. The light was packed and sealed at an indoor temp of 75 deg. fahrenheit then left all day in the vehicle with the outside temperature reaching 107 deg. F., 120+ in vehicle.
The UT20 was removed later in the evening, indoors and simply felt for anything higher than 'cool'. Upon opening the bottle, I could feel the inner part of the lid was warm so this wasn't good. I then unwrapped the light and it was warm.
So, basically, these bottles have little to no lid insulation and/or the heat is able to transfer from the lid exterior to the air inside the bottle. An Rtic or Yeti could be tested but I'm not willing to waste that kind of money. It needs a radiant barrier for the lid. The wally world bottle would keep the batteries at an acceptable temperature with it stored in a bug-out bag that is removed from the vehicle each day.
But, I'd still like to find a way for this to maintain the start temperature.
I don't know if it actually works, but someone I talked to stored his battery cage in a plastic bottle with cap and wrapped the aluminum bubble type wrap that some use to insulate exterior walls in canada with to the outside of the bottle and cut a round top and bottom as well. He says it keeps his batteries "safe" in hot summers. I may try that one day and see how it goes myself.
Why don’t you just store some CR123s? Makes much more sense to me. Li-Ion batteries are meant to be used.
There is a PDF from Energizer on this topic. CR123s will still have 60% of their capacity after 4 years at 40°C (not just the summers!)
1,5V Lithium AA/AAA batteries would be even better. They need to sit for 15 years for the same effect!
What I'm looking for is maintaining them at a cool temperature. So, this first experiment provided proof of concept, or not.
I've been storing 3*C cell form lights in the vehicle for years and using an adapter for primary lithium (AA 1.5V). CR123s out-gas alot so I'm not too crazy about that. It seems it is much less with the high quality Li-ion cells.
However, until I can maintain the temperature at a cool level, slowing that chemical reaction of discharge, primary batts. are the main option.
Why not get one of those indoor/outdoor thermometers that have a remote sender for outdoor temp and use that for real time monitoring of the temp inside the packaging being tested?
Nah, I just wouldn’t. Wouldn’t pay trying to keep ill-tempered cells in an environment that just pisses ’em off.
eneloops would be the best candidate for hostile environments like car interiors. If you need a Li-based cell/light, I’d just keep one on my person and use that.
Or better yet, disposable alkaleaks, kept OUTSIDE the light, unless you want ’em to take a royal dump inside the light and permanently ruin it. Keep a working set, and a set of spares.
That's why I sort of like the lights with the rubber flap on the charge port. Often I have inserted a battery and the flap pops open which tells me at least it would allow a battery to vent instead of building up all that pressure inside the battery tube.