Put in the center console, the trunk or anyplace out of direct sunlight should be perfectly fine with brand name quality 18650’s.
Left in direct sunlight should still be ok technically but you would be a bit closer to the rated limits of the cells for my tastes. In the sunlight it can get to around 140-150f in a car, 18650’s are generally rated to at least 175f. I would not recommend this even if technically ok.
I left 2 lights with 18650’s in my car all summer last year in the Texas heat. Like I said, no issues and still fully charged after this winter hit it as well.
The voltage was at 4.14V when tested a few weeks ago as I stated above, I charge all my cells to 4.18-4.20V to start with and I turned the lights on briefly to make sure they worked.
So I doubt the heat had any measurable effect on the voltage over the normal self discharge and the use that they had.
As far as long term capacity loss in the cells, I highly doubt there was any measurable loss there as well.
Capacity. Voltage will always stay the same at full charge, even if 99% of the capacity of the battery has been lost.
High temperatures age li ion more rapidly, Nissan had huge problems with their EVs in Arizona because they were not engineered for hot temperatures.
Being a Texan also, I’ve not noticed any problem with Lithium-ion cells in a hot car. They are being stored in heat not used in heat. Self discharge will be higher, cells life cycles should stay about the same. Panasonic list storage from –4 F to 122 F but discharge from –4 F to 140 F.
Its a well known phenomenon, higher temperatures lead to faster battery aging and capacity loss.
In fact the Chevy Volt uses its air conditioning to keep its batteries cool on hot summer days.
It does reduce the lifespan, the question is by how much? I am not worried about a 20% loss over the course of a few years. Small price to pay for a nice high power light when I need it.
Astrolux S1 fits in one of my flipdown overhead console compartments quite nicely, with easy quick access even in complete darkness (if truck has complete power failure). Seemed the most flexible choice for least dollars.
I don’t keep any lights in the car, unless you count road-flares.
Whatever I’m carrying is what comes with me in the car.
’Though if ever I had to pick one, I’d pick a zoomie, despite my generally disliking them. A fixed aspheric would be nice, or even a mule. For getting a tire changed, I’d rather have all-around light than a single hotspot and lesser “spill”. So my choice would probably be a SK98. Maybe a Match-mod Minimag with wide-angle TIR or just as a mule.
What I keep in my bag, I’d likely have a light for every occasion.
That only works for so long. a Coolers aka insulation doesn’t keep heat out indefinitely. It just slows down the rate at which the heat transfers from the outside to the inside. OTOH, I agree that a smaller cooler just big enough to hold the light and maybe extra cell(s), and stored under the seat or in the center console would be better than just the light itself.
I keep a 20 year old 4C Maglite with a 140 lumen terralux led upgraded bulb and a glass breaker end cap in my daily driver. I religiously check the alkaline batteries for leaks and keep a fresh set of alkalines in the door side pocket. I like the glass breaker and club factor if need be.
I know its old school but the light has sentimental value and so far never let me down.
Plus I always EDC some sort of 18650 light in my pocket and another in my backpack in case… those always get changed out from my collection depending on what I feel like carrying for the week! :+1:
