18650 flashlight to use and leave in car

Should be ok. Same cell as used in laptops, and same chemistry as every portable electronic device, and those are left in cars all the time.

Should be fine, unlike butane cigarette lighters. I have seen a few explode in cars on hot days.

Personally, I make it a point to only leave alkaline/lithium primary battery flashlights in the car but that’s because I prefer to be cautious. My choice is the Fenix L2D with 2 primary lithium AAs.

If u use rechargeable lithium cells, there are some precautions u could take to reduce the risk:-

- stick to single-cell lights.

- use protected cells. Laptops and hand phones use lithium cells too but they are packaged with a protection circuit board that prevents over-charging or over- discharging.

- look for lights with low-voltage cut-off.

- if the flashlight does not have low-voltage cut-off, test the flashlight now and then n if the light is dim, measure the voltage of the cell before u recharge it. I try not to let my cells fall below 2.8v or thereabouts. If it does drop below my threshold, I would pay special attention to it when I recharge.

- of course, try n keep the flashlight in a cooler part of the car rather than exposing it to the sun.

I am sure there are other points but these are the ones that come immediately to mind.

I don’t like leaving a LIion light in the car in the summer either. I have see the inside temp of my car above 125F in the summer at work many times.I’m sure the cells wouldn’t explode, but it can’t be good for them either.I usually just leave a couple of AA lights in the car with LSD cells for the summer…no worries.Now that is starting to cool off I will probably leave my Romisen T602 in the car…it will be neat to see what effect the cold will have on the 18650’s output this winter.

Should be fine. Just put some good batteries in it. I left a 2 cell XM-L flashlight in my wifes car for several months. It did fine. And that was through the heat of summer.

It is perfectly safe to leave a Li-Ion 18650 in a car, hot or cold. It won’t explode or cause issues in that regard.

However, high heat is very bad for Li-Ion cells especially when fully charged, as it reduces recharge capacity even when not used. Since an 18650 is being used in a flashlight, it will be charged to 100% and then stored in the hot car. This is the worst scenario for a full charged Li-Ion cell. Keeping it at normal room temps or even cooler is better for longevity (charging to 40% and then storing in a cool location is the best method). It won’t cause any dangerous issues, but the life of the cell will be greatly reduced when left for weeks or months in a hot car. After just a couple of hot summers with minimal use, the cell will start to show serious capacity loss, which is a waste of such a good battery.

As others have mentioned, a low self-discharge (LSD) rechargeable NiMH cell like Eneloops are fine for a hot/cold car. They will hold a charge for quite a while and no issues with life cycles from the heat.

Thanks bfksc…thats what I was afraid of, damaging the cell.So LSD in the summer, and LIion in the winter it is!

If your light can take 6V then you could use 2x CR123s which have a 10 yr shelf life and safe for long term storage. A number of US sellers stock 123s for under $2.50 each so you could buy a small stock and have them on hand for a long time.

Great, thanks for all the advice. Any recommendations for high output flashlights (500lm +) that run on conventional aa or aaa, even cr123as, that are <50?

Actually, use LSD just in the summer, and Li-Ion spring, fall and winter. It’s just in the hot months above room temp (70’F/20’C) you want to avoid Li-Ion. I have a single AA cell LSD flashlight in the car all year for emergency backup, which gets a fresh cell spring/fall (unless it gets some decent usage). And I keep an 18650 flashlight in my daily carry bag for general use. The backup is really for my wife if I’m not with her or for some reason my carry bag isn’t with me or my main light fails.

As for buying AA cell lights, you’re not going to get a truly bright light (500) from single or double cell AA lights. You can expect about 100-150 for single and 200-300 lumens for double AA cells using NiMH rechargeables. For more light, you need more voltage and/or more current with todays LED emitters. I’m sure you can find many lights that advertise 500, but they can’t truly deliver that kind of output as AA cells just don’t have the current flow.

And as for brightness, 100 lumens of out the front (OTF) light in a dark place is actually quite bright. For typical night time tasks like taking the dog out, walking to the mailbox, looking for something I dropped, whatever, 10 lumens is plenty. To see what that bunny hopping around under the backyard table is doing, 80 lumens is plenty. To find out what’s making those growling noises 200 feet away in the bushes, well that’s when you want 400 or more.
:bigsmile:
To be honest, my 18650 light produces about 425 actual lumens at max, but I rarely use that much light. I use low/med at about 10/80 lumens most of the time to cast enough light for many tasks. For roadside emergencies, 100 lumens is lots, and 10-20 is enough to see what you’re doing to change a tire on a dark road, or look for the baby soother on the floor or something in the trunk. You don’t really need hundreds of lumens for emergency backup in the car. It’s nice to have higher modes with more output, but in practical terms, you don’t really need it.

Personally I’d go with a 502b host and either find or make a dropin that could handle 2 123s.

I’d probably also make it an OP with a diffuser and go with an XP-G2 or an XML T-6

Another option (and probably going to be contested) nebo redline, 3x AAA, you can pick one up at basically any gun store they are cheap and have a magnet in the tail to mount while working.

Also has my favorite implementation of FTT

While ago when I researched laptop batteries (Liion of course), experts mostly aggree that temperature is death for Li-ion cells. It ruins their capacity.

BTW, regarding storage of Liion cells, some measutestsrements were made, and result was that its best to store them 40% full.

I would advise, because car is moving thing, to have some light that cant be easily turned on (and undervoltage proteciton would be great too :slight_smile: all this what other said)

Haha, I actually go driving in the mountains a lot. Me and my buds like to stop at the vista point late at night to chill and relax. It’s practically pitch black there, and the possibility of a wild animal lurking in the bushes isn’t impossible. :wink: Plus, if one of our cars were to break down, etc, having a really bright light that can light up the whole area is really useful.

Jetbeam PA40 is close to 500 lumens, you couldn’t tell the difference with your eye. If it was to be left a long time without use I would use Energizer Ulitmate Lithiums in it, but if I was to use it now and then I would go with eneloops.

Also you could get a Solarforce L2 (or something similar) and use 2 cr123a batteries provided you get the right voltage drop in.

Usually I have at least one edc, many times 2 (main and backup), so that's more effective than leaving a flashlight always in the car. Easier to find on my belt, and sure I know if they are charged or not. Left forever in the car I'm gonna forget when I charged and would end up unusable when needed most.

Anyway I would not trust a rechargeable left alone in the car, because of high temps ruining the cells in the long run, plus the self discharge of cells gets worse with extreme temps (hot and cold). I think primaries are better for this, due to the lower self discharge rate, but anyway one would have to adhere strictly to a routine of swapping them annually with new ones.

so, how sensative to temps. are cr123a?Does high temp. effect the shelf life? And by how much?Are they safe to store at 125F?

The ShiningBeam Blaze is a little more expensive than a 502b, but I can wholly recommend it. You can feed it 1x18650 or 2xCR123, and it’s super bright with none of the heat management issues common to lights in this class, as it’s reasonably driven at 2 amps and the pill is securely mounted inside the head. The streamlined UI stays out of your way, the build quality/finish is exceptional, and the seller ships wicked fast.

I got my Blaze as a ‘blemished’ model (I found a tiny nick in the anodizing when I got it) back in June and I’ve put it to work almost every night at my summer job. I’ve dropped mine on rocks and concrete and got mud in the cooling fins (a dunk in the lake took care of that). The thing looks brand new aside from two small chips in the anodizing.

The UI lets you click away on the switch without changing modes, which is taken care of by loosening and tightening the head. Only thing I don’t like about it is the strobe, but the UI makes it easy to live with. It throws well for the reflector size and the 1A tint bin has won me over- it’s free from blue and green hues that plague many CW lights. The Blaze is a superlative light in the do-it-all 1x18650 class IMO.

-S.P.

Well, not that CR123 are happy about that hot in the car, but in the worst case the safety vent will bleed some pressure and keep them safe.

Cannot get for you any number, but have read that primaries do self discharge less. When you buy them there's always the shelf life stamped on.

From SureFire’s website,

“Wide Temperature Tolerance

Lithium batteries greatly outperform alkalines over a wide temperature range, providing a working output from –76º to 176º F (–60º to 80º C).”

So, they ought to be fine for the car unless you leave you car parked in Death Valley 8)

Wow that seems like a really nice light. I love the battery indicator. However, it’s a little more than I’m willing to spend on a flashlight at the moment…