Head "torch" almost turned into an actual flaming torch.

Blimey! There are many places you don’t want a lithium cell going thermonuclear. The forehead is definitely one of those places!

Reminds me of a watch where the "QC OK" sticker inside was essential insulation of the battery spring. But then there were the IBM har drives where glue from "QC OK" evaporated onto the platters...

The quick escalation in tools used to open this device had me cackling. Vise of knowledge: 1,000 : Hard to repair devices: 0

It’s unfortunate this thing is so poorly isolated because I am sick of eBay headlamps with there never ending strobe features! Great video 👍

Don’t use Efest 18650’s they’re notorious for venting. I own a vape shop & in order for me to get insurance one of the deciding factors was if I carried that company or not. Could’ve been a fine battery, but if the wrap was torn on the positive end.... venting occurs

I'm really surprised that there was no reverse polarity protection considering how lithium cells can be quite outspoken about being made unhappy.

Don’t trust any battery with fire in the name.

I love it how you ramp up the voltage to twice it's normal working voltage, to test where it's shorting out, whilst holding the very thin circuit board between your fingers - with every chance of pressure popping the IC and sizzling your fingertips. A good ounce of bravery that!

Oh man, so many implements of enlightenment were used here!! How exciting!

This manufacturing oversight has enraged me. I shall write a very stern letter to eBay and CC all it's customers.

RIP Big Clive's favorite headtourch

Truly scary... with the incredible popularity of rechargeable devices containing high capacity (high energy) lithium batteries, often with sub-par manufacturing quality control, it is only a matter of time until they become a cause of house fires, even if not in use or being charged. Lithium batteries in the 2020s are going to become the danger 1970s aluminum house wiring became in the 1980s.

I bought a couple solar powered motion sensing lights like you took apart a few months ago. Saw one with a popped out side panel LED so took down the unit it to reattach the LED panel. Turns out the 18650 battery shot out an end cap and a spiral of paper/electrodes, physically damaging the housing! Glad it didn't set my shed on fire.

I have 3 of the same kind. For the price they are very good. I have used them a lot for over a year now, as i work with stuff during night and there is no electricity around its gets very dark early at this time of the year (northern sweden). So far they have worked perfectly, one battery ain't what it used too and the rubber at the charge port fell off on all of them after a few charges, the ring at the led gets loose sometimes. Besides that it's all good. After seeing this I won't have all three charging beside my bed all the time... Great video.

I was really looking forward to seeing what comes after the Dremel tool.

If you manage to non destructively open the other one you could protect the board with plenty of kapton tape which obviously should've been done from the factory

Interesting and alarming at the same time.

Hey clive, the springs are what prevented thermal runaway. because of the heat they compressed/shrank to the point where it couldn't complete the circuit. I've made some "powerful" flashlights which draw way too much current for the little springs (up to 15A with a single cell is the highest so far) and lets just say i've been there before... we flashlight "enthusiasts" get around that issue by using better quality springs and "bypassing" them with a stranded silicon wire connecting to the end of the spring and to the base so that it remains springy but can handle much more current. (also lowers resistance so that a FET or direct drive flashlight can be a bit brighter) If you're looking for a new headlight, Skillhunt is a very well liked budget brand around the enthusiasts. the H03 variants are very popular.

I use a headlamp with three lamps where you can adjust each one individually (only vertically). Really nice thing from Aliexpress for like 15€. Adjusting each lamp individually is really nice, because you usually not turn your head most of the time but just your eyes. So for example I put the smaller lights downwards more, so I get light there. Can highly recommend such a headlamp.

Another interesting video as always Clive :)

That's the reason why i use a protected 18650 in my Alonefire flashlight. A brand with fire in the name indeed but very good! :) Quality looks really nice and there goes also always a extra plastic protection around the 18650 delivered by the torch. You could also use it with 3x AAA in a converter. But also then is protected 18650 a good extra safety feature

I only use LEDlenser torches, because I am convinced that these are the only really good torches. As a head torch, I use a MH3, which takes one AA cell, has 2 brightness settings (when you don't change it for a certain time after pushing the button, you don't have to cycle through it to turn it off), and no more bells and whistles. But it has a really great and bright light, which can even be focused by rotating the lens (I don't need that feature, but it's cool to have).

I'd highly recommend the Nitecore NU25 as a replacement. It's lite, multi-functional, USB rechargeable and very bright.

Likely simple explanation: Raw springs are inherently dangerous around the pos end of an 18650, particularly on a screw cap. There's only around 1-2mm between neg and pos (case and pos cap) at the pos end. It's extremely easy for a spring to displace / unwind and short the cell. Edit: your hypothesis about board shorting to case is also plausible.

On a somewhat related note, it still boggles my mind how the hell those PCB-solderable metal clips that are meant to hold regular batteries are still on sale, legally - those things short out batteries BY DESIGN. In addition to touching the two poles of the battery they also clip onto the cylinder itself - which would be fine except there still are batteries around that have a *lacquered metal* cladding, not a plastic one; and as soon as the super-thin lacquer layer is scratched by insertion on both ends, you have a straight path from one pole through one clip onto the metal cylinder onto the other clip onto the other pole - so you can have a battery start getting warm with nothing but the two clips attached, right in your hand! Which of course actually happened to me with the first battery I tried these accursed things with. Also - the same thing can very much happen with plastic-clad batteries too, it's just somewhat less likely the comparatively thicker plastic cladding will get damaged on both ends. But if it does, same thing...

There was a recall on electrically heated underware that used the very same battery holder. Great balls of fire.

Also note: Lithium cells can randomly short out internally. This can be encouraged with over charging, over discharging or being dropped. That is why every one of the 8,000 or so 18650 cells in a Tesla Model S battery pack is fused. If one cell should go screwy the energy of the 90 or so paralleled cells wont dump into it.

Clive you are an electrician.. you like the light and how it functions.. insulation and modification is the answer :)

Clive. Sorry for your loss, it's horrible loosing a good friend. But you had me thinking, of all the torches I've owned that you stuff the batteries in like that one, they all had the battery going in + first.

Thank you Clive. I enjoy a good autopsy, though you do not come to a certain diagnosis but rather the conclusion that the torch is just garbage, with which I agree. This particular torch seems to be a mere prototype that was rushed to market. At this point in time plastic would be the best material for the case, if we exclude environmental concern from the equation. Machined aluminium for a torch is just archaic and more marketing hype or "steampunk" than anything else. I have owned a couple of Maglites. Great art but absolute nonsense. Negative earth is pretty much the standard for DC systems, since about 1960. The battery compartment cap, if you notice, grounds the battery case to the torch case, so it is a safe bet that the negative end of the battery belongs at the cap. The battery's positive end has a very small dielectric gap to its surrounding case. You are right, if you think that the cap spring shorted the battery's positive pole to the battery's case. They are incompatible. The large negative surface on the other end of the battery could have also shorted to positively charged metal on or around the circuit board. LEDs are diodes, so correct polarity is required for them to emit light; right? This is not to say that the circuit board could be designed to correct for a reversed battery but that could be suicidal in a single-insulated system, with some of the solder so close to the case. I have a far superior head torch that is mass produced by a battery manufacturer, Energizer, which was perfect in all but one way, ironically: wasting batteries. Its big momentary button switch would accidentally get squeezed on, in my backpack, briefcase or pocket. So I always carried spare batteries on desert hikes in the mountains, after having repeatedly discovered fully drained batteries. I remedied this design flaw by making a plastic battery isolater out of a bit of stiff plastic product packaging. It is just a strip, 5/16 inch by 1 1/4 inch which I slide between the positive end of the battery and the terminal. It folds 90 degrees to lie flat on the battery, and I snap the case closed, to store. Batteries seem to last forever now.

Get a Fenix HL55. I've used mine for several years as a mechanic without battery problems or failures. It doesn't have the IR on/off though. No flashing modes either. Just some brightness levels and it remembers what setting you left it on. Nice flood area effect light, no dark rings in the beam. Also, it takes 18650 batteries.

I had the same problem with a night scope I had. It was a Gen1 thing but still a nice thing to play with at night, a bit grainy and limited vision but you could still make out what things where. It had an infra red LED for 'lighting up' the area in front. I must admit the instructions did say to remove the batteries when not in use, but I obviously forgot about it and it was sat on a shelf for ages until I went to use it again and saw the battery cover was warped and the 2 AA Alkalines were utter destroyed and had ruined the contacts and of course the thing wouldn't work any more. I took it apart and those night things are really weird. It has an anode wire and must work like a TV Tube in reverse, gathering light, amplifying it and focusing it onto a phosphor screen. It's a shame and was an expensive lesson to learn and I don't think I would buy one again. I don't know why the batteries shorted out but they clearly did for some benign reason lol :)

I wanna see you make a steampunk polished version with copper and soldering now. The basic geometry really is kinda simple.

Hi Clive, Here is a thought.. I think like the makers of the head torch expected the reverse polarity protection to just short out the cell with a diode and rely on the PTC in the cell to limit the current... except that since the torch was designed 18650s without any PTCs (or ones that trip at many 10's of amps) are now common, such as your Efest... When the fault happened, the battery spring did got very hot, losing its temper so breaking the circuit like a thermal circuit breaker. This unintended (and fortunate) "feature" of the battery spring may have saved you from the "lithium Battery incident". Applying a short to a battery pack can cause battery springs to softened the plastic they are mounted on and , break the circuit that way. This is the fun part of product safety testing :-) The LED looks like Cree XM-L.

The plastic insert centres the battery. You also had the bench power supply connected two different ways, positive on spring on one test and on the outer rim on another test, would that make and difference?

Suggested design improvements within concept and price limitations: 1. Positive contact is just a bare pad on a PCB, optionally pretinned. 2. Non-ground tracks are run mostly on the inside, using the PCB itself as isolation. 3. Pushbutton is replaced by a touch contact on the outside of the bottom PCB. 4. Inside surface of PCB covered by strip of electrical tape. 5. No waving detector.

an so the mystery of more SC becomes apparent.. ty

1 it's a lemon (lomon?) 2 the battery label has flames What did you expect?

7:51 "Oh so it's still working!" Pity you've just done a hatchet job on the case LOL

Lucky that battery has a safety circuit built in or it would have exploded and probably set something on fire. Had a 18650 nearly explode in my hand the other day as i was chucking it out the window after a short circuit occurred and it has began to smoke. You have to be so careful with these batteries. Dont forget the entire outside of the battery is negative and only that small part on the top is positive so its so easy to short them out.

It still works. Cover the board in silicone and slap a protected lithium cell in it . You'll be fine.

Well done, Mr. Holmes "Clive"

The springs make excellent heaters in case of a fault. The scaring has nearly disappeared now. End caps and their springs are - only.🤕

_Clive they'll short out on their own. I've had a couple of unopened, "Trust-Fire" 18650 2-packs from the cheap Chinese Flashlights, have 1 of them get burnt just sitting in the box._ _I've cut the blue outer covering off some of them only to reveal a black heat shrink covering that says "Panasonic"._

I know from experience with cheap powerbanks, those spring terminals really don't like much current. I've had a few glow and one melt.

The housing will be positive when you put the battery in backwards. It looks like the sleeve around the battery was damaged, this exposes the "unsleeved" metal of the battery that is negative. You will get a short circuit if that unprotected metal part of the battery comes into to contact with the positive housing of the lamp, when you put the battery in backwards.

be glad it didn't short out and catch fire when it was on your head also the spring acted like a fuse on the negative terminal it should of had a different insulator and batteries don't like short circuits

Battery guidelines have always stated that batteries should be removed if not using a device for an extended period. Modern advice for lithium powered devices recommend removal of said batteries where the device will not be in use for 7 days or more.

Looks like it had an internal spring clip that retains it. I've used similar clips in my designs when they're not meant to come back apart. Makes assembly convenient, but its pretty much trash if you f up. Also the spring clip itself may also have been the alignment mechanism if the groove in each section doesn't go all the way around.

I was looking at headlamps for a gift and came across one on amazon that had 2x 18650 cells in a plastic pack on the back of your head with the light up front. One of the comments was that it was had a hard wired parallel connection with no reverse polarity protection so if you put one cell in backwards it would be in full short with the other one. Nice. If a UK manufacture wants to make a product they have to meet all kinds of stringent safety regulations but chinese stuff on Amazon is made to whatever standard the chinese manufacturer decides which usually means nothing with the fake CE logo slapped on it.

Dremel, spanner, blowtorch, genteel deconstruction, or what? Clive another fantastic,, informative and entertaining production. Thanks for sharing I have an early gen led lamp (Tesco... Who branded tech! :) that seems to have been the source of my tears of x10 lighting gremlins.read sinetgi g about filtering online but never did anything about it. Also a 13a through adaptor with 2xusb sockets. Never worked. Just send me a sign, it would be a pleasure. Cheers from the fatherland (unwanted relation that is the disfunction uk Gary from England

I think the idea of using a cylindrical O ring sealed sealed aluminium casing for a torch probably began with the American designed Maglight. Many other companies like FENIX and LED Lenser followed the same format. But used a battery casement and switch module. So they do NOT use the case as part of the circuit. However even with that format; I have had problems with some pretty expensive ones. Yet my cheapest LED torch £5 has been very reliable and that DOES use the metal body as part of the circuit.

I guess you could apply some kapton tape to the upper side of the PCB and any other problematic areas which may short and that will "fix" the design problem. It will be effectively insulated and the kapton is thin and sturdy enough to withstand the use and any potential heat.

The cheaply made internals could pull more amps out of that quality cell then the tail spring could handle, then the front spring had the same issue. Solder a piece of solder wick from the tip of the springs to the base of each, then you can suck the juice out of the cell faster without worry.

I've got a headlamp which takes a single AA that comes on in a low power state when the battery gets low, slowly flattening the battery even more.

I'm glad you made the knife safer by going VVVVVVVVV, it makes all the difference

Wtf?! I just had this problem last week and now you make a video about it?!

Remember this applies to DC power, Commonly if there is a spring that is connected to the metal body its the negative, Clive will know this but just putting it out there as reckon its simply a oversight as he is extremely knowledgeable with electronics and i will never say a bad word about him, I dont know a quarter of what he knows and unless the day comes that i know more i will always have faith in these videos Also imagine if it popped like those vaps with dodgy batteries, almost guaranteed blindness as your eyes would be mutilated by the debris and chemical fire

I'm watching this while on the NYC subway controlling myself from screaming at my phone "tighten the vise of knowledge!"

P.S. Also look into the Pelican offering. I love mine and found it for about $25. (It uses 3x AAA batteries.)

Also had a powerbank doing this. It wasn't even plugged in, but randomly it started melting. Cell was shorted.

Hey Clive. Which bench power supply are you using? I’m looking to get one.

Solder joints on the board could be making contact with the metal body, same as with some of those cheap pen light things B&Q sell

Do you think that c clip was locking the cap on? If so maybe it could be removed without damage and properly insulated and reassembled. Looks like a very nice light if not for the lack of insulation.

A very serious design flaw in an otherwise nice light. Lithium cells pack a ton of power and you really don't want all that power released as heat on your forehead ! They could've easily solved the issue with some extra insulation above those solder joints.

Hey Clive, does that head lamp have any protection circuitry built in? Because it would appear when you pulled the wrapper off, the cell did not. If the cell was discharged under 3 volts a few times, that may have caused the electrolyte to crystallize and create a short inside the cell itself. Not saying that is what happened, but it is a possibly.

Hey, it makes the cell go thermonuclear but at least it still works afterwards :D

Clive the cell has vented as it has probably overheated they have an internal pressure relief in the cap. Don't touch the electrolyte!!! It is likely flourinated and will burn you and stain you black. Always wear nitrile gloves when handling questionable Li-pos. Get a viton burns kit as this can neutralise such a burn. Lucky it didn't go up in flames, the newer higher power density ones are not so forgiving.

Believe Olight also makes a headlamp that has simple features and I believe it has a red night vision mode but it’s very pricey over $100 but olight is the Cadillac of the Flashlight world so I don’t think they have any torches that are below 50 bucks.

If you want something to go BANG!!! you could do what I accidentally did 25+ years ago in High School Electronics class... We had to build an Electronics Kit (I choose a huge digital clock) and accidentally wired the Step Down Transformer in backwards... It was supposed to take the 120V mains and drop it to 5V...instead, it took 120V and stepped it UP to 2,880V...1st time I plugged it in there was a BIG BANG and a simultaneous thud above us... The transformer got literally blown off the board and embedded in the drop-ceiling tile above me...Scared the hell out of myself and the Teacher... Surprisingly, after replacing the transformer (and making DAMN sure it was wired in properly), everything worked...still have it in fact, but I need to replace the LED's of the display board...too bad. the think was so bright I didn't need a Night Light... :D

You should insert the battery with the negative end touching the spring. The spring will force its way in between the positive contact point and the negative rim if you insert the battery the wrong way.

Am I correct to assume "skidmark" does not have the same connotation in Glasgow as it does in the US?

I could not see any discolouration at the point where you suspected it to have contacted the casing, shouldn't there be some? Could it have been the solder blobs in the intersection of the boards contacting the end cap, the spring clip or some other part in there?

Clive, the little spring on the round circuit board is correctly off center, but the one on the screw-in cap is not. That one, for obvious reasons, is perfectly centered, so not hitting the center of the battery. Not an issue on the negative. But if you inserted the battery with positive toward the cap, screwing it in might have allowed the spring to get through the insulation and short the cell on the + side directly ... The main source of heat looks to have been there. Could it be that the torch was almost fine, just the plastic liner and the spring suffered a bit from heating because of puncturing and shorting the cell + insulation with the cap's spring?

how to isolate that contact in the other one ? drip feed 'some/alot of' superglue ... can the solution be tested, if not bad luck, or then he has 2 cylindrical cases to make a nice paperweight ...

That’s a cool knife I do not believe you have talked about it before. I like the low profile. Where did you get it?

In my experience, negative usually goes on the spring

Since you have already ordered a new one...check it out...they may have addressed this issue in a newer unit.

This is the best head lamp IMO. Just with they would use a wide lens. I end up taking the lens off of mine to get it wide but the led is exposed that way. Also the IR on/off is the dumbest thing ever if you work in any tight spaces.

Is that a "real" brown skid mark, or is it just dust from the Dremel cutting disc? Seems to be right under the part you cut through. Also, assuming the problem was indeed contact between the board and the casing, can't you insulate the other (ex., with a thin cardboard shim)?

One would think that anyone who's seen a careless vaper with his trousers on fire, would think twice about strapping an 18650 to his forehead.

I purposely reversed mine once because the led was remaining on very low and was once told reversing would " straighten" out the problem. Immediate overheating. I was able to shake out the batteries before ruining it, however the springs had both become "un springy". I stretched them a bit put the batteries in right and it worked fine, albeit with led still low when off. Pretty sure it would have gotten vey nasty if left in, however batteries didn't get hot, just the springs.

I had one of these head torches. It delveloped a fault where the light was flickering so i took it apart to try to fix it. The end cap is just a press fit on the main body and requres a good hit on alternate sides to get it off. The brass coloured ring should be soldered to thd round ciruit board and I beleive is intened to create a contact between the main alumium body and the cirtcit board to complete the negative supply to the board. In the end I couldnt get it to stop flickering and it eventually it failed altogether. Also, it was not at all water resitant, the usb port and holes for the IR transmitter and receiver being the areas that will easliy let water in. I have replaced my old head torch with a different model that again uses an 18650 battery, incorporates usb charging but does not have the IR facility. The USB port on the new one is located under the end cap that partially unscrews to reveal the port and has o rings to provide some water resitance. It is more compact and weighs less than the old head torch, has 5 brighness levels and cost the same. Easily found on ebay from a number of different sellers.

I feel like mag lights do this too! They get warm and also they don’t last very long. And don’t even get me started on the crappy keychain ones! They last a month or two at best with limited use.

Enough of a scare for me, I've just removed the 18650's from my torch and laser pointer. If I want to use them it only takes a sec to pop a cell back in. Also marked polarity on the torch - like yours, mine is unmarked.

I've found that every flashlight, or any other thing requiring batteries... The negative end of the battery always goes toward the spring.

I have a Fenix brand headlight made using the same flashlight body. Must be the same factory. Hopefully mine never experiences the same malfunction.

Would it be worth your time to put kapton tape over the top of the board, using a hole punch for the led's and maybe conformerly coat it. And is there room for a protected battery?? Seems like a good unit with just a slight error they didn't think of..

efest misrepresent their battery specs so that probably doesn't help

I love the flash function on headtorches. It anoyes the out off my co workers when I talk to them.

Have you looked at 265 nm led? Be interesting to see if they increase the power.

I think it has come up before, but where do I get one of those box knives?

efest cells. dont buy anything other than sony, lg, pannasonic, samsung.

Your battery might have spun inside of the case and the spring might have gotten under the insulator at the positive end which is really close to the negative side of the case where it's crimped

did you charge it differently somehow? some of those chargers seem to blow batteries if the input isn't just right.

Hi Clive, I share your passion for finding a pearl in chinese pile of turd, but for such an often needed tool that I put on my forehead in an inch of my eyes I prefer the cheapest PETZL. This model use to be called TIKKA but quick googling showed there is a new generation of the model and there is now an even cheaper model called TIKKINA. It's plastic, it's not particularly bright, it's relativelly expensive, but it's lightweight and the thing that goes south first after intensive use is the very soft and nice to touch elastic band, however it does not degrade ugly, but just stretches and becomes partially loose which is easily compensated. Not a comercial, I'm sure there are many other reliable brands.

Weak link in the design. And I have the same one. So, is changing the battery causing the wear on the anodized layer? I'm trying to think of a reason to keep using mine, but if I do I'll definitely charge it in my explosion resistant cookie tin. I actually charge everything in those now. One of the best ideas I've learned from Big Clive.

If you could get the other end off reasonably, disassemble the other one, and wrap the board in Kapton or maybe sections of shrink to insulate it?

May be the spring turned between the plus pole and the case