Nope
You are equally likely to be impaled by the flashlight, so there’s that. :bigsmile:
I’m curious is 4V is enough to start a gasoline fire, is there a voltage threshold that something is considered automatically intrinsically safe?
Buy a diesel car instead? 
Doesn’t even need volts, all you need is a spark, can you make a spark by smacking metals together?
4V is not by itself enough to start a fire or even produce a spark that I know of. What can start a fire is the disruption of a cell which releases chemical energy in the form of molten contents and very high temperatures. In other words the uncontrolled release of the chemical energy in a Lithium Ion battery as talked about in the Smoke & Fire forum on CPF
Also 4V or even 1.2V is enough to light an incandescent bulb of low enough voltage so run through the correct gauge wire could heat it enough to possibly set off gasoline vapor I suppose. I bet that you would have to work at it though.
There would be a simple way to prevent this virtually impossible occurrence, store the flashlight in an airtight container
The battery will still age quickly form the high charge and high temps, but you won’t start a fire that already is not going to happen
that might be a much higher voltage :nerd_face:
Murphys Matches law.. The flashlight will end up in the gas tank and explode get de-domed 
I think its more Tom E’s law :bigsmile:
If you crash hard enough to damage a Li-Ion cell inside even the cheapest flashlight, a short leading to a gasoline explosion is the least of your worries. The EMTs collecting 100% of the scattered body parts is issue #1.
based on some good input, I think that an 18650 based flashlight is not a good choice for a hidden in the storage area for years emergency light in a car. (still got 4 18650 lights in the house and more coming)
I am going to use a Maglite 3D LED unit that I got at half price along with some new 2024 Costco Duracell D cells that cost $1 each at costco.
Am I paranoid or simply scared
Or are my fears generally shared
If forewarned is forearmed
I should not be alarmed
And with caution from peril be spared
4v is enough to make a small spark, whether that spark is enough to ignite gasoline vapor, and under what conditions, I don’t know. But that isn’t the only way 4v can start a fire. Pass enough current through a conductor with enough resistance and you might get temps hot enough to cause ignition. I’d guess an 18650 has enough energy/power to start a fire this way.
None of which are worth worrying about for an 18650 in a flashlight though, because as has been said, the conditions under which it is likely to be damaged enough to start a fire are probably unsurvivable anyway, that, and there are better choices for a battery for an emergency light.
They are quite serious about it because they have regulatory and insurance requirements to deal with. They have regulatory and insurance requirements to deal with because their exposure to risk can be a lot higher than 1-2 cells in a flashlight. They could have 1-2 cells in lousy packaging, next to a mislabeled package full of di-ethyl ether starter fluid, or 1,000 in good packaging, or, in the case of a 747 filled with the latest iPhone, 195,000 pouch cells in one aircraft. Clearly they are willing to carry a literal shit-tonne of lithium batteries, provided they are confident in the quality and packaging.
Under high temps both the old “Heavy Duty” carbon-zinc D batteries and alkalines have a high probability of leaking and destroying the light. I just had a batch of USA made D alkaline batteries leak in their original package THREE YEARS prior to expiration date and they were stored in my house. There is a reason they are known as Alkaleaks among many BLF members. The supposed long shelf life is at about 68 degrees F or 20 degrees C. Cook them in a car and forget about it. Energizer lists operating temperature as 0 to130 degrees F. Car interiors often exceed the high end in the summer outdoors and in many areas get colder than the low end in winter. Cold alkalines have minimal capacity while cold too.
As I posted earlier it will be hard to beat either CR123A or Energizer Ultimate Lithium primary batteries for a car emergency light based on makers specifications. Alkalines would be one of the poorer choices. Good LSD NiMH batteries would be much better if recharged every six months to yearly. In fact ALL emergency equipment should probably be checked yearly for problems.
I may be prejudiced, but I tend to trust the people who invented the technology. They have the most “skin in the game”, IMNERHO.
Here’s what Sony found, when they were developing Lithium ION (NOT Primary Lithium) batteries:
| Crushing test | Fully charged | 20 ± 5 °C | The battery is placed between two parallel flat steel plates, such that the electrodes are parallel to the plates, a force of 13 kN is applied. No rupture or ignition |
| Impact test | Fully charged | 20 ± 5 °C | A round rod 8 mm in diameter is placed near the center of the battery, parallel to the electrodes and perpendicular to the direction of the upper terminal of the battery, and a 9 kg weight is dropped from a height of 60 cm onto the rod. No rupture or ignition |
From their Lithium Ion Technical Manual …
Sony did a lot more scary things to their nascent batteries, which I invite you to read about (knowledge is power) so you can decide for yourself. The part where they put a fully charged one in, essentially, a dead-short rig until it reached 0v without any “vent with flames” BS was especially interesting to me.
As for me, I did what you’re suggesting. I built my first flashlight mod, a 2C Maglite with a Sears 6-cell-compatible, PR-based LED and 3 CR123 batteries in a soft plastic filler tube from Home Despot to make up for the smaller diameter. You’ll have to dig into some serious archives to find out when that was the State of the Art!
It’s still in the glove box and still kicks out the most awesome Bright White Light (with that same lame Mag beam) any time I pull it out. I made another one for SWMBO, and she uses it constantly. I’m trying to wean her onto LiIon-based P60s (because CR123s are still mind-bogglingly expensive), but that’s another story.
I wouldn’t mind using LiIon, but the self-discharge rate prevents me from trusting it for the kind of long-shelf-life, ready-when-I-need-it solution the Primary Lithium gives me.
Just my two cents worth.
Dim
No more dangerous than the fuel in your tank, or battery under the hood. Or other vehicles on the road. Like that CPNG bus you passed!
All honesty aside:
I think you are on the right track. I actually have the same kinda light rig. I use the Mini Mag Pro Plus 245 lumen and have the Energizer Lithium. Stored one in each vehicle as a back up to my other backups. So, I guess I am paranoid, just in a different way. 0:)
Of course, I normally have 3 or 4 other lights with me too. Likely have some 18650’s in my bag in a case too. Been carrying them for years. As long as they are high quality cells, charged & stored properly. No real worries for me.
Most dangerous for me? The .50 Action Express ammo under the seat!
No, you are not paranoid. The voices in my head told me that all batteries are out to kill you. They are OK with everybody else, the just don’t like you. Save yourself a gruesome battery death and just off yourself in a painless manner… hurry… they are coming for you… we’ve tracked the volts to your house. J)
Yeah, just think of all the cars that go off a cliff and explode in a huge fireball before hitting the ground! And then there’s Spirit of ’76, which made fun of the then-current brouhaha over Ford Pinto gas tanks exploding in rear-collision accidents by having a careening car come to a screeching halt an inch away from a Pinto, with the latter exploding seconds later (after everyone heaved a sigh of relief).