The freezer was set for -2° F. Two thermometers in there were reading -10F and -30C. I did it in two batches. The first batch of nine lights was left in for 30 hours. Before placing them in, I turned all of them off while in the lowest setting so that they would come on in the lowest mode. I immediately clicked or ramped up to the highest setting on all lights when taking them out one by one. None of them would go to the highest turbo. They did all appear to get to a good high setting except for one of the S2+ which is stuck in a 50% mode. I was initially going to charge everything to approximately 4 volts but just decided to put them in as they were. I measured the voltage of most in the first batch before I put them in.
Wurkkos FC11 3000 button 3.93V
Convoy S2+ Imren (MJ1?) 3500 3.82V
Convoy S2+ Imren 3500 4.06V
Convoy S2+ Samsung 35E button 3.79V
Armytek C2 WR 3200 3.35V
Armytek C2 limited 3200 3.96V
14500
Lumintop FW1AA YLD 1000 3.7V??
Lumintop FW1AA YLD 1000 3.9V??
18350
Armytek Tiara C1 sofirn 850 button 3.92V
The second batch was only in for 5 hours and I did not measure voltage but they were probably all at or just under 4 volts. All 18650.
Armytek C2 Pro Imren 3500
Armytek C2 Pro nichia armytek 3500
Wurkkos HD15 3200 button .
On the first batch I only ran each one for about 10 seconds as high as they would go. On the second batch I ran them up as high as they would go and left them on for 5 minutes while continuing to try to get to the highest turbo but they would not do it. The two armyteks did appear to get to their lowest turbo setting which is about 750 lumens and the other one around 800 lumens without problems. The wurkkos was doing pretty good even with both LEDs on.
I have been leaving many lights in multiple vehicles and some have been in there for 7 years. Almost all 18650s. I bring them in to charge after I’ve used them to some degree. 2 that have been in my wife’s vehicle never get used. I check them occasionally. It used to be every year, now it’s every few years. I’ve pulled them and ran them for 5 minutes and then charge back up to 4 volts two or three times in 7 years. They see 0 F a couple of times every year and 100F occasionally in the summer.
I will keep using lithium ion 18650 rather than lithium primary or NiMH for storage in vehicles.
I would worry more about the degradation of the Li-ion batteries from overheating during prolonged storage in a vehicle than a temporary performance decrease while frozen.
If you have an analyzing charger, it would be interesting to see the test results for the capacity and internal resistance of the batteries that have been stored in your vehicles for 7 years.
Your vehicle’s interior temperature could considerably exceed 100º F depending on the intensity of and elasped time in the Sun along with the vehicle’s characteristics (like darker color, if it has a sunroof, whether the windows are left open, etc.).
If you’re looking for cold performance then I’d grab some Molicel cells. For the cells I’ve looked into their datasheets (P45B, P30B etc.) they all specify down to -40 for discharge.
Most of my other cells (30Q, NCR18650GA) are only rated down to -20C.
Anicdote: I’ve been using a P45B in an S21E, overkill yes, but it has been working great on my walks in -20C.
FWIW, I had a bunch of 18650 cells, all new, harvested from unused laptop packs. They did track pretty closely when tested on an Opus.
I put one in the freezer at 3.7v. I’d leave it in there for months, take it out to warm, then do a capacity test on it and compare it to a couple others that had been kept in a fridge at 3.7v. Cells were otherwise unused.
In about 2 years the ‘frozen’ cell started to deviate and degrade more than the ‘fridge’ cells. It was a single tested cell, of an uncommon brand (that has turned out to be lackluster, but not duds), done once. It’s a data point, but not necessarily a good one.
I agree it’s not good for the batteries. I don’t see it as practical to pull the lights out of the vehicles for certain parts of the winter and summer. That would defeat the purpose of keeping lights in the vehicles for when and if I need them. I also keep battery operated power tools in the work truck year round. Those batteries have definitely lost a lot of capacity.
I decided to run one more batch through the freezer and I turned it down to the lowest setting. The temperature ended up being -20F, -29C. I was going to take a sampling of the 10 or so lights in the vehicles but decided to just do the two that had been in the wife’s
vehicle the longest. Although I think the Atactical A1s (name changed to Wowtac) has been in the work truck longer than those two. And for the first year that Atactical was in the work truck I stored it up on the dashboard where it meets the A pillar. So it probably got really hot in the sun on occasion.
The two that I put in the freezer.
Olight S2R baton 3200 proprietary.
Wowtac A2S 3400 with micro USB
I did not measure the voltage before I put them in because I had checked them probably 2 months ago. Both came on without a problem and ramped up to high but could not reach turbo. After about 3 minutes the wowtac was able to go to turbo which I recall being around a thousand lumens. I ran them both for about 5 minutes. 20 minutes later I measured voltage at 3.94 on the olight and 3.8 on the wowtac. I really should have measured before I put them in.
The point of doing this was just to see what I might expect if I had to use any of the 10 plus lights on the coldest nights that we experience around here.
I do believe that charging to 4 volts helps limit degradation to some degree in these poor storage conditions while still providing plenty of capacity. I do not have an analyzing charger so I cannot measure capacity or resistance.
If you experience colder or warmer temperatures than 0 to 100F your results may vary.
