# Headlight batteries SAFE??



## thermal guy (Oct 29, 2018)

I have started to use headlights more and more because I’m starting to realize that they are very useful in the woods. But every time I strap one on I’m always wondering what the he’ll would happen if that big old battery blew? I have used rechargeable batteries for some time. Always top of the line ones and have never had one single problem. Has anyone had one go off in there headlight before? Not talking about something you heard or rumored to of happened but actually had an experience like this?


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## Szemhazai (Oct 29, 2018)

Battery ? No never. Short-circuit inside the wire is quite common in some headlamps, but usually it end's up with totally discharged batteries, no smoke or fire.

In over 200 headlamps that I've fixed only 2 have visible marks of the temperature damage.


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## Crazyeddiethefirst (Oct 29, 2018)

Hi Thermal Guy,
I have a pretty good size collection of lights(over400 lights), with at least 1200 batteries(10180 to 26650), and the only time I have ever seen anything close to a thermal runaway(precursor to a possible explosive event) is when I have been way overtired and done something stupid(example:I like to have lights with matching battery carriers, so to go with my Emisar Collection I purchased about 12 extra body tubes in various colors and 24 caps. I did not think about the fact that these were not designed as body tube caps, they were the actual tail caps off of lights. Long story longer when you put a fully charged 18650 cell into a contained space with springs ensuring full electrical contact, bad things happen. Fortunately, when I am “playing” with lights, batteries and chargers I always keep a couple of “charging bags” around that are designed to contain a Lithium “problem” so when I realized the incredible amount of heat coming from it I dropped it in the bag and muscled one of the caps off to stop the problem. I guess my point is that in thousands and thousands of hours of use, I feel that with a little education and common sense they are very safe. If you were wearing one when a short happened, I would have to believe your reaction to the heat of a short would lead you to intuitively rip it off your head and toss it away before it reaches the explosive point. I have read about 3 or 4 cases where some did not realize the importance of “matching” cells in multi-cell lights and this led to an issue. Someone posted the video of a guy holding a two cell light in his mouth that had 2nd & 3rd degree burns-he was intubated (had a breathing tube placed in his trachea) for a few hours out of concern for damage to his lungs or poisonous fumes-luckily he had no such problems and was talking to a reporter 24 hours after it happened. Please note, my experience is using all types of flashlights, not just headlamps but for all the hours of use, including a lot on aircraft from puddle jumpers to Jets, boats and everything in between, lights and lithium cells are very safe...


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## ven (Oct 30, 2018)

I use a headlamp every day during week(might start using one at night walking, but they can be annoying unless walking alone!.............so jury out on that one). I only have 18650 lamps, simply because of the run time and output needs, anything less for me is not enough. On my head most of the time are vtc6 or 30q cells. Never once does an explosion enter my head(in either way i guess). Granted on a hard hat, so maybe that plays a small part. But honestly , the only odd time anything like that gets thought about, is when vaping some times(that would make a mess). So i have things in place which reduce said potential(rare) issues. Good cells, good charger, good torch, good practice!. 

Charge cells outside of lamps(if lamps have internal charger or not). Replace cells off head if prefer, that way its easier to deal with(throw away and run ). Test prior which i think we all do anyway, to fitting on head/hat/helmet. I think time/confidence over a period of time is your best friend with this, if cell/s get heavy use, replace after a couple of years from trusted seller. Maybe a little over kill, but depending on use it keeps things newer. I do with my vape cells, at around £12 or so($15 ish) for 2 , hardly an expense which gets stuck near my face! I am no oil painting, but heck, i dont want to smudge the paint more! 

I also lock out the lamps in between uses, luckily its a little turn of cap to do so(convenient) .

On cells exploding, i know a work friend it happened to at his caravan. He placed a cell on the charger and it almost instantly went up, not over sure which it was. He is confident it was down to a split wrapper. He did say WOW , it was discharged(again unknown V) ready for charging, it made him appreciate the energy even though not in a fully charged state. Luckily he threw the cell/charger away fast and out. He blames a torn wrap near the positive end, so shorted. Needles to say, always inspect cells regardless of device for wrap condition, its not much separating the + and - (disc and wrap) from each other. 

So personally never, only one i have known(not read on news) is down to damaged wrap at + end.


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## thermal guy (Oct 30, 2018)

Thanks for all the input guys.


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## StorminMatt (Nov 15, 2018)

The whole idea of strapping an 18650 to one’s head has been a troubling one for quite some time. But I believe that it can actually be pretty safe, especially when compared to other risks in everyday life. I myself have been routinely using an 18650 headlamp since 2014. In that time, I have probably hiked HUNDREDS of miles with my headlamps. As with ANY use of lithium ion batteries, LOTS depends on the quality of your equipment. If you use quality cells, the risk decreases GREATLY. Also, risk is reduced if the light has a good low voltage cutoff. Most of the time, the light will reduce brightness before cutting power. Replacing your battery at THIS time (rather than waiting for cutoff) is MCH better from a battery safety/longevity standpoint.

But perhaps the most important thing to consider is that the likelihood of a battery incident in a headlamp is virtually ZERO. Unless the headlamp is of such bad quality that it malfunctions and shorts a battery, there is VERY LITTLE chance that your battery will cause you problems. If a battery is going to ‘go off’, it is most likely to do so while charging.

With this said, I should also mention that I feel that UNPROTECTED cells are the safer choice. Unless you are using a garbage headlamp, a short is most unlikely. But with protected cells, there is always a chance that the strip from the positive terminal may short on the can. Not to mention that it is probably more likely that a protection circuit (which is out in the open and vulnerable to physical damage) will short than a light.


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## Beendare (Nov 26, 2018)

I look at it this way; There are more than a Billion cell phone and computer devices out there....and we very rarely hear of an issue. Pretty amazing really when you consider how the Li ion batteries are made. The most notable are the Teslas that have damaged the battery in an accident. 

It is worth noting the major Li ion Battery mnfrs recommending charging in a non flammable area. 

I think a guy would feel it before the battery on your forehead heated to 1,000 degrees.....

Anyone worry about electrical pulses? The Black diamond Storm I had [for a short time] had a hum to it.......that unit had to be giving off more [??] than the cellular waves folks were worried about years ago.


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## iamlucky13 (Nov 29, 2018)

Personally, no, but I don't have a large number of lithium ion batteries, and I follow the recommendations for them.

The cases of lithium ion batteries experiencing thermal runaways that I have heard of mostly related to a few fairly specific problems:

1.) Cheap cells from unknown brands, especially when used in high drain applications (I've heard a few stories of e-cigarette batteries cooking off in purses and pockets, and know of at least one video of it happening).

2.) Manufacturing defects, such as assembly damage that was implicated in Samsung Galaxy Note fires that were happening not to long ago.

3.) Cells physically damaged in use, such as the occasional crushed mobile phone, or Tesla that has been in a serious accident.

4.) Cells that have been electrically abused (eg - over-discharged, over-charged, etc).

These are reasons why I don't personally recommend lithium ion battery powered lights to people who don't seem interested in learning the basics of caring for lithium ion batteries, but I don't see the basics as difficult to learn and follow for anybody who is interested in doing so.


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## patricio2626 (Dec 3, 2018)

You just had to go and put this doubt into my head, didn't you?  I hike with 18650 headlamps and really haven't thought much about this. Now, I stepped up to the big boy and bought an Acebeam H30 with the 21700 battery yesterday. I guess that monster's a real hand grenade if it runs away! Regardless, I'm going to use it anyways. As previously stated, you only hear bad stories occasionally and we have tons of Li-ion devices.


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## LogansRun (Dec 18, 2018)

To the OP, you've raised a really good question. I have only had one incident (since 2008) where I had an 18650 short out due to ingress of water, in what was supposed to have been a water resistant light... I had given my light to a friend at a bar and I guess he had spilled some beer on the light. Luckily for me, there was no thermal runaway, just smoke.

Now, I have been using a Zebralight 18650 headlamp for a few years with no issues but I try to be aware of any adverse weather conditions and remain vigilant that I keep moisture away and o-ring seals lubed up to prevent ingress of water.

As others have pointed out, our mobile devices all use li-ion batteries and, the best we can due is just maintain our vigilance. Also, iamllucky13 pointed out some good recommendations on reducing risk and of any issues.

I liken this to any other potentially hazardous items in our homes... whether it be gas stoves, propane tanks for BBQ's, etc.


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## Szemhazai (Dec 19, 2018)

LogansRun said:


> I had given my light to a friend at a bar and I guess he had spilled some beer on the light. Luckily for me, there was no thermal runaway, just smoke...



I'd rather say that he was checking it's beerproffnes inside the mug .


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## LogansRun (Dec 19, 2018)

Szemhazai said:


> I'd rather say that he was checking it's beerproffnes inside the mug .


LOL! Nice shot! Sadly, the light I had suffered a worse fate than the image above, i.e. besides the battery, the LED was ruined. Hmm... I wonder if beer has a way around o-ring seals or if the light just had terrible waterproofing.


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