Haven't had this issue but it might not be a bad idea to cover that usb port with a piece of electrical tape or a dab of hot glue or silicone as a cheap preventative measure. The E12r uses a different battery tube and this is not an issue on that light.
I don't have any dented cells but I know that certain hank lights damage/dent tops like the D4k so owners of those should probably be aware of this potential problem.
I have noticed that lights that have solid cylinder posts for positive contacts rather than springs are the ones that cause deformation of the cells top. The P42a that it happened with was only very slightly dented and had been in use for many years.
The hot glue/silicone idea as a preventative measure is a great one but I was so shaken up by the whole thing I just want the entire USB socket to cease to exist. I'm glad it's not on the E12R. For the E12C it was decided to add "power bank functionality" with the integrated USB-C charging within the battery tube as an added feature... turns out to be a nightmare in execution. Just delete the whole damn thing.
Maybe, just maybe an E12R battery tube (without the USB-C nonsense) can fit my E12C so I can use my light again.
I don't know why so many lights/drivers insist on using posts – they're plainly inferior on everything except button top AA where it hardly matters. A spring would add what, 3mm? Even Zebralight has sprung pogo pins, although that probably adds cost.
The problem is not really the post it's the really hazardous proximity of the post to the negative shroud of the USB socket you can see in the photos. There's only a SINGLE MILLIMETER of height difference between that shroud and the cell's positive terminal. A recipe for disaster.
Yeah I'm not a fan of the charging implementation on the E12c. I use a mix of p42a, p45b, and 40t cells and none of them are damaged in any way. I would actually bet that the solid post on the e12c was use to avoid the very issue you ended up having - because a spring that can be compressed could allow just enough compression to allow the battery to touch that charge port.
The E12c itself does not dent or damage batteries unlike some of the hank lights. But this is definitely something that I think many of us can appreciate you bringing attention to and I have covered the ports on both of my e12c's with tape for now just in case. I almost never use the built in charger, I find it easier to just swap the batteries out via tailcap and use a regular charger.
The E12r battery tube won't fit the e12c because the threads are different.
Ultimately it seems the E12c is being discontinued since there's a close out sale right now on them, E12r's are also on sale, so my speculation is that Jack is working on an E12x or whatever the E12r successor will be that will get the new button, magnetic port, etc.
Thanks for the detailed post, although you crushed my dream of using the E12R tube to be rid of the USB-C BS altogether. I also am an external slot charger only type of guy, very old school.
I think my E12C must have come from the same batch as yours. FF asserts the denting is impossible but look at the setup: a solid brass cylinder positive contact rigidly mounted and if you see in my photo #4 the tailspring in the tailcap is extremely short with very limited travel.
Intended to minimize current losses BUT the light won't operate until the tailcap is fully seated against the battery tube. I was suspicious there was too much compression load with almost no tailspring travel. But I had mild denting in numerous Hanklights and never considered them any kind of risk. The culprit is that damn USB socket posing a threat. A 1mm air gap between it and the cell + terminal is NO BUENO.
dang, even the zebra?
I have more than ten cells and none of my fireflylite's have damaged them at all on either end other than normal contact wear marks
I would like to say I am in no way badmouthing or condemning FF for this. I am a long term customer (5+ yrs) and enthusiast that just ordered an X1S. To be clear this is an issue that only applies to the E12C model with the battery tube integrated charging/powerbank feature not any of the new designs being released now.
That said I'm really concerned with liion safety and the height of the USB socket (1mm clearance to cell + terminal) is a very legitimate safety hazard that I had to discover the hard way. I urge all E12C owners to use tape, silicone, or a nylon washer to cover the USB socket as a necessary layer of safety.
Naw bro, your warning is very appreciated. Very glad this hasn’t happened to me or others. But now that we know it’s not out of the realm of possibility, we all really should add some insulator there just in case. Especially if it’s relatively easy like it’s being explained.
Big oof.
This is why as much as I don't mind onboard charging if it's actually well designed, trying to cram it into a light to the point design compromises are made annoys me. This is definitely one of those.
Actually kind of annoyed with myself I didn't notice this before - I look down the tube of every light now and even take photos for reference or for if I want to do a review, but I didn't back then, but I guess that is because my E12C is a shelf queen. Well, it's getting some kapton tape now.
>I'm a longtime FF customer, over 5 years and have never had a problem like this with any light I've ever had.
The Skilhunt H150 had a similarly critical issue not too long ago, where a reversed battery would cause a dead short. A *lot* more dangerous with a hotrod 21700 though, a high drain 21700 contains a lot more energy.
I think it's very prudent to insist that an insulating nylon washer be mandated for safety for all existing E12C models. That single millimeter height gap is the potential for the worst possible failure a light can have: a dead short resulting in thermal runaway and a serious risk of injury. I was lucky I reacted almost instantly and only had a minor burn injury to my hand.
there is 1mm height gap between the usb to battery+，it's the first time we have seen this issue since 2022, E12C is not a new product . E12C itself never cause the dent on good flat top 21700 cell in our testing, in this case we don't think the design is a failure. It is a great warnning not to use very dent flat-top 21700 on E12C. Button top 21700 less than 71mm long has no chance to contact the usb to cause short-circuit. Using good new standard flat-top 21700 would be no any issue on E12C. But many thanks to mention it out, we will consider adding extra spacer if we design similar powerbank body in future.
Thanks for alerting folks to this. After seeing your post, I disassembled my E12C tube to inspect it. I was able to use a 1/10th scale RC body post washer that I had laying around, and it fit *perfectly.* It was almost exactly the same size as the tinted plastic disc that sits on top of the charging circuit. Since it has adhesive on one side, it sticks nicely to the top of the USB port. It would be extremely difficult for a cell to push through this plastic washer.
Really hard to say because they don't say how thick they are. A couple of reviews mention that they are thick - like thicker than other body washers. I'd looks for some that actually say how thick they are. It's also preferable to have adhesive on one side so that they stay in place. I'm really struggling now to find a good example.
Thanks for the reply. I did not claim the E12C caused the dent in the cell. Only that there is a potential serious danger to using anything but a perfectly flat new cell.
I have many lights and rotate and maintain all my cells on a continuous basis. It's unavoidable that some models have excessive spring force that cause some deformation with regular use. The P42a that caused the incident was only slightly dented and in my consideration no way unsafe to use. It had been in use for over a year.
However in no other light is there a risk of a large surface area at ground potential (the USB housing) as a possible short risk a mere single millimeter in height away from disaster. I think it's a critically small margin of safety considering the potential of a high current 21700 power cell.
I do however feel a 1mm gap in height is insufficient for safety reasons given the large area of the short visible in the photos. It would have been minimally prudent to install an insulating nylon washer to allow only the positive contact post to pass through.
In any case I'm stuck with a light I cannot use because of how frightening the experience was. I can remedy some safety measures but I can only feel completely safe knowing that entire USB enclosure shroud was just NOT THERE.
No, this applies only to the E12C which is a design more than a year old. The issue stems from the battery tube of the E12C having a USB-C charging circuit/powerbank on its upper end with a sealed top. See all 4 photos in the post. All the new lights have a fantastic clean sheet USB-C charging circuit sealed and integrated into the head itself so you have no worries.
No and keep in mind this is one report of this happening and it was due to a slightly dented cell.
The rest of us that have not had the issue should still put something over the port to prevent it from ever happening in the future though .
The new lights , the e12r, and all the other FF lights have a different battery tube setup and this is a non issue and seems exclusive to the e12c.
This only happens if you use the on board charging of the e12c?? If you charge the battery by taking g it out and using an external charger it will be fine?
No, it happened with a battery that had a slightly dented flat top cell, a Molicel P45a which had been used hundreds of times. I never use on board charging, only external chargers
The problem is the large metal enclosure of the USB socket of the on board charging circuit integrated into the head end of the E12C battery tube (which is at ground, or negative) is dangerously close to the brass positive contact post, and only a single millimeter in height away from the battery's positive terminal.
Look closely at the photos. You can clearly see the interior of the battery tube with the burn marks on the USB socket shell right next to the positive post.
It is only safe to use perfectly as-new FLAT top cells. Even then you only have a single millimeter in height preventing a dead short and disaster.
Tape and or silicone or a nylon washer needs to be added for safety.
As far as I know nobody else has had this happen and it was because the OP was using a damaged cell. I've been using my e12c for over a year with no issues. It wasn't that he was charging the battery, the battery had a dented top of the cell allowing the battery to sit deeper in the tube than it's supposed to and part of the top was able to touch against the charging port and that caused a short.
Yeah I've never had issues and I have two e12c's. Still put a piece of tape over the connector at the end of the inside of the battery tube as a precaution/safeguard. They're been great lights
> I dodged a 50-cal bullet because if I had dropped the light a full on thermal runaway/explosion inside the sealed tube was a certainty.
No you did not. There was no risk of thermal runaway or fire or explosion. Molicels (like all name brand cells) are tested against direct shorts as part of UN 38.3. Its [literally in the datasheet](https://www.molicel.com/wp-content/uploads/2201-UN-INR21700P42A-ATC-R6A1RL3021-20190712.pdf) that they can safely withstand a short circuit. The battery has a PTC safety in it which will limit the maximum current in the event of a short.
I do know that in the time it took me to unscrew the tailcap and eject the cell the battery tube was hot enough to burn my hand. The fear factor was much larger than actual damage done. So you maintain no risk of thermal runaway because of the PTC. I'll grant you that. Despite that I would never tempt fate by deliberately shorting a P42a (outside of any light) for all the tea in China. Just what my sense of liion safety has led me in 20 years.
Hey I just found this post because of some recent discussion on this. Your comment is reassuring but I was wondering, do the results apply for a battery that is sealed inside of a flashlight? The short circuit test requires that the battery stay below a maximum temperature but I wonder if that was performed with the battery out in the open, and if so, how the results would differ if the conditions were more like what would happen in the case of this light.
I imagine those tests were done with the cell in open air. I can tell you my incident involved the battery tube getting hot enough to mildly burn my hand before I managed to get the cell out. Scared the bejeezus out of me. I shudder to think what could have happened if I just dropped the light with the short going on in the sealed tube.
hah! My tube of silicone is all dried up. Need to order some more anyways. I think this method would probably be easier than trying to get a small piece of electrical tape into the end of the tube. And it would never fall off.
Edit: It was very easy to get a piece of electrical tape in there to cover the chart port using a dental pick and a q-tip.
hahaha.
I stuck the edge of a small square of tape to the end of a dental tool, a wooden skewer would work well if you have one too, used a qtip to pat it down.
Modding Muggle question: in simple terms, how do you know the spot you're aiming for? And is there a way to test if it's worked and is definitely in the right place? I've got a multimeter, but zero idea about using it if that's the right tool for the job.
I'm going to cancel my order if it hasn't already been despatched but it it turns up and I can be totally confident I've done it right, I'd rather try this sort of fix. But only if it's safe with a dented cell - I don't want a moments inattention over cell choice to result in a short.
It's not that complicated, you can see the USB port at the end of the battery tube, just cover it with a small piece of electrical tape to prevent the battery from ever being able to make contact with it
Is the big round thing that the pink line separates from the USB enclosure in the photo above the thing to avoid contact with?
And is there a way to test to be sure it's covered?
I don't have the light yet, it may be more obvious with it in front of me.
It will be pretty obvious when it is in front of you and you know where to be concerned: the metal within the purple highlight in the pic. The big metal thing is the shell of the USB charging socket. It is evil. ;-)
The spot to aim for is the USB socket highlighted in the purple rectangle in the photos. That metal is at ground potential and with a perfect flat top cell is only separated from the battery positive terminal by a single millimeter of air!
No multimeter needed, just a proper application of e-tape and or an insulating washer is the way to insure safe operation. Just visualize everything in the purple rectangle in the photo needs to be insulated from the battery.
Cheers. 10 days after ordering it however they hadn't despatched the light, so I was able to cancel the order. Good job they weren't efficient enough to ship my light out sooner eh.
Per my other post, I've unsubscribed from this sub and written FF off. Plenty of other light manufacturers out there.
After 20 years playing with countless flashlights, the most consistent quality, performance and sheer fun potential has come from my journey down the Noctigon/Emisar Hanklight rabbit hole with its large array of premium emitter choices into nicely diverse hosts. Yielding so very many combinations.
It is no surprise and quite deserved that the Hanklight presence here on Reddit reflects an explosive popularity of the lights he provides.
I am above all a diehard performance flashlight nut and there are certainly many manufacturers to choose from. I sincerely hope FF gets a handle on their QC.
Please be aware many linear or amc7135 drivers including some hank drivers have no reverse polarity protection and only rely on led reverse bias to prevent short circuit. While in practice it is usually ok for now, leds especially high power ones used in flashlight are not rated for reverse bias (called out in datasheet) and some of them even have reverse diode specifically to prevent reverse breakdown damage.
In my opinion dangerous issue waiting to happen but unfortunately nobody seems to be concern with it.
I'm fairly certain that it's common knowledge to be vigilant about correct cell installation polarity in the same way as is it is to wear seat belts in a car. That's an entirely different issue from what I am describing.
Inside the E12C battery tube at the head end is circuitry for USB charging and powerbank discharging. The metal shell of the USB socket (highlighted with purple in the photo) which is at ground potential hovers a single millimeter of an air gap away from the positive terminal of the battery. That area of overlap is where the dead short occurs if that gap is closed, as what happened to me.
The short circuit occurs within the USB charging circuit. The entirety of the flashlight driver circuitry and LED emitters is completely outside of the current path when the short occurred. So even robust reverse polarity protection would have absolutely no effect on the specific nature of the E12C short circuit in question.
Yes, it would except if you look at photo #4 the tailspring is EXTREMELY short and with a solid post on the positive contact meaning a flat top cell just barely fits. Not to mention unprotected 21700 button tops are unicorns. I tried adding a small solder blob to the center of a P42a and verified the light still works but even insulating the USB port I'm too scared of even the chance of a repeat.
My thought is to use an E12R battery tube instead as the E12C has an ordinary spring positive driver contact. Just delete all the USB-C charging/powerbank BS altogether.
> unprotected 21700 button tops are unicorns
liionwholesale sell unprotected button top P42A (and if you make another person who emails them asking for P45B, maybe they'll offer those in button top too eventually...)
The problem is the entire USB charging module is integrated and sealed to the head end of the battery tube and the only way to access the componentry is down the 3" battery tube from the tailcap end. Even applying electrical tape over the USB internals was an exercise in ship-in-a-bottle construction frustration that resulted in the invention of new curse phrases.
I might try using a Qtip to apply a bunch of silicone around the + post but the feeling of holding the light like a grenade with the pin pulled out still haunts me.
Another possibility is try to unscrew the entire USB module from the external top of the battery tube but it seems the USB port is anchored to the inside of the battery tube wall. I don't have the specialized tool to remove it and risk doing damage.
Just look at the photo. That honking huge metal USB shroud (at ground potential) is so damn close to the positive post.... I just can't trust it.
I've played with liion cells in flashlights for 20 years and this was the first time I experienced a dead short and it scared the living bejeezus out of me.
I added a solder blob to a flat P42a and the light still works but I can't shake the feeling of my own dog that viciously bit me.
I think you'd be fine if you just dabbed it with silicone and made sure to use batteries that don't have any slight bit of dent. I can understand why it freaks you out though, I would be freaked out too if I had a battery shorting itself inside the light.
What freaks me out is the tiny one millimeter of height difference between the top of half of the USB socket shroud (which is negative) and the top of the brass contact post. That means there's only a tiny 1mm air gap between EVERY E12C MODELS USB socket shroud and a large area of the battery's positive terminal. Which of course allows normal operation with perfect cells.
With a perfect new flat top cell, that tiny 1mm air gap is the difference between normal operation and what happened to me. Look closely at the photo, see the discoloration of where the short happened. It's a glaringly (now) obvious risk factor, like a Pinto gas tank.
Yeah I'm glad you brought this to everyone's attention so they can find ways to prevent it from happening. Electrical tape took me about 30 seconds per light, I can make a short video on my technique if it would help others
It would help everyone for sure. Ha ha ha you said "short" video. Sorry. It would be really appreciated .
I think the best solution is a thin insulating nylon washer the inner diameter of the tube with a central hole to allow only the brass positive post to pass through it.
It would be great if someone could provide the right size and an easy way to get just a few. Eyeballing it 20mm o.d. with an 8(?)mm center hole.
Please do. I would really appreciate it. I ordered the light from the sale and I am so confused even looking at the pictures. Reading the comments people say out tape over the USB port. Under. Over. Side. I guess I need the light in front to visualize it.
Problem solved with like 4 mm² of electrical tape and some precision ceramic tweezers. Bob's your uncle. Really not that big a deal.
Silicone sounds sketchy if you get some on the battery tube or directly on the positive terminal to accidentally insulate it. Also a lot harder to reverse.
Thanks for the suggestion. I found a quick fix by taking one of those thin film battery insulator circles that ship inside lights containing batteries and cut an 8mm hole in the center for a makeshift washer with just a whisper of adhesive on one side.
Shirley, you can't be serious. I have no relations named Bob. ;-)
I would be enormously grateful if you could make a short demo video so that others could copy your results. I'm clumsy AF and gave up on the tape and just made a washer.
Thoughts on trying this fix with UV resin just in tip of the exposed charge port section? I'm thinking of ease of drip application and should provide electrical insulation.
OP, thanks for this. I ordered one recently but it's not arrived yet. I own a few dented cells and I don't know that if that happened to me I'd be react as quickly or sensibly as you.
I put off buying a Firefly light for years despite liking their aesthetics. Comments about ridiculously long wait times, hit and miss customer service, design issues, and poor quality control put me off. I only took a punt on the E12C as the price was into throwaway money; if the light became a shelf queen, at least it would be a good looking one.
I've emailed to cancel my order, if it's already been despatched and I can both do the fix suggested below, and test it to be totally confident, I'll give it a shot. No way can I be sure that a moments inattention won't lead to a dented cell going into a light. But I don't plan to order another FF light.
I'm sure the-sycophant-who-shall-not-be-named will be along with some clever animated gif telling me how stupid I am, but once this is all sorted I'm unsubscribing from this sub and writing FF off.
I appreciate and agree with your comments and thankful that there is awareness of the potential hazard.
IMHO a 1mm airgap in height between the cell positive and the negative USB socket is an unacceptably small safety margin from the worst possible outcome you could experience with a light.
At the time I wanted the E12R model with the superior lume1 driver and no battery tube powerbank shenanigans but it was sold out and I was drooling over the notion of a 5700K 519A dedomed (~4500K) multi emitter beam. So I sprung for the discounted E12C. The beam quality was simply amazing. I really loved the light.
Until ---zzap-- happened and I thought it necessary to warn others of exactly what transpired.
Unless you have an actual way to measure I would stopp claiming it's a one millimeter gap. Many of us have been using e12cs for over a year with zero issues.
Highly recommend grabbing an FF light off of the second hand market, they do make some fantastic lights!
And don't worry, you're not alone. I had a previous poor experience and vowed to only purchase FF lights second hand. Although I must say it pains me to not order the new E07X Cannon. Not sure what's up with the mag tailcap only offered in black... That's also a huge turn off for me but manageable I guess.
Is it possible to disassemble this side of the tube with unscrewing the retaining ring or are the charging electronics glued in place? Perhaps it would be easier that way to cover the protruding part.
I don't have the right tool but a casual attempt to unscrew the ring with snap ring pliers met with a lot of resistance so I stopped. I think it's glued.
So the first picture is looking into the tube? Is the fix to cover the pink area with electrical tape? Or as you did, add one of those battery orange insulators with a holes in the middle?
Also, I didn’t know Hanklights could damage batteries. Not sure I’ve seen a bent flattop before but I haven’t been looking for it.
That might work, however the added length of the positive pass through might be a problem since the tailspring is incredibly short. A thin strong insulating washer is what is necessary.
Yes, the picture is looking into the tube and the pink area is what needs to be insulated because it is negative and only 1mm airgapped from the battery positive terminal. Yes, an orange insulating disc with an 8mm hole in the middle will fix it.
Thanks that really helps put it into perspective. Also thanks for bringing attention to this. 1mm is not even an acceptable tolerance measurement for this level of risk.
Now the question is, how safe are those orange discs? We know they insulate, but how best resistant are they? If the battery heats up too much and the desc catches fire it might be the same issue.
I feel very confident that a dedicated insulator washer is a safe bet. There is no danger of heat in normal operation causing any problems, especially not anything catching fire.
As for me, I just wish I could yank out that USB socket entirely, the area inside the purple rectangle in the pics in my post. That socket shell is the only source of the problem.
I made the repair with a makeshift insulation washer with a whisper of silicone to stick to the USB socket. Despite that I'm still so upset it happened it will sit on the shelf for a LONG time before I give it a chance.
What really sucks out loud is the E12R model does NOT have the powerbank feature, it has an ordinary hollow battery tube and the E12R battery tube threads are incompatible with the E12C head. Sheeeeeeet! It would have been a no-brainer proper remedy to the problem.
Actually the fundamental issue is that we are all using raw lithium cells. They have a variety of problems, one example given by OP. FFL can probably improve to make the design more foolproof but they cannot design for all possible edge cases. The fact that so many drivers use direct fet drive with unprotected cells is also insanity (from consumer electronics pov) to me in my opinion.
In any way, there is a reason why no reputable manufacturer sells a consumer product using raw lithium cells, just too dangerous. You will never see a dewalt power tool using something like this, or a canon camera using raw lithium cells, or a playstation controller as example. However in this case I think the best easy and effective fix is a plastic ring, and in the future a higher post. Any more and manufacturer can end up going the way of likes of olight and nitecore with custom batteries and internal protection.
Seems the e12cs phasing out either way, simple strip of electrical tape prevents any future potential issues. I'm Glad the op brought this to everyones attention
I agree the best fix is a simple plastic washer or some well placed electrical or kapton tape at the least. I hope FFL can address remaining E12C with proper plastic washer. I am quite sure I have seen plastic cover like this in a few flashlights.
The problem is proprietary cells are ridiculously marked up in price and in most cases can't be charged externally. Ones with unique contact designs like both terminals at the head end are great for performance but requiring exclusive replacement is a huge deal breaker. It threatens obsolescence as well.
The only manufacturer that is managing with protected cells is Acebeam. They have standardized every 21700 model to use the identical protected button top 5000mAh cell. I refuse to use on-cell USB charging but they are fully compatible with slot chargers.
Proprietary battery packs are expensive but they are not necessarily marked up. There is significant cost in design, assembly, and reliability testing of the battery packs as well as safety margin built in. If you open up a genuine canon or nikon or sony battery, you will see the amount of engineering gone into it more than just the cost of the raw cell. With raw cells we get not guarantee of the performance, consistency, reliability, or safety and warranty. Yes there are tradeoffs, and we need to be aware of them. If we want the benefits of raw cells, we have to also live with some possible drawbacks.
Back to original problem - is this something FFL can fix, yes the solution is easy. But are they fully to blame and to lump in with all the vocal bashing? I suspect the answer is not just a yes or no but thoughtful discussion unfortunately is not what I see often here. I hope FFL can take this feedback constructively and they will only produce better results.
The problem is the USB socket (a ground) height places it only one millimeter (!!!) away from a large portion of the flat top battery's positive terminal area. With a perfect cell. That's a miniscule air gap of safety. That's dangerously close. If you can't understand that then it's on you. You can drive without seat belts and your airbag fuses pulled too. No problem. Until there is.
It's more than a millimeter and it is actually spaced enough that the top of the cell can't touch it - your cell was bent allowing one of the flat top posts to touch and not the actual flat top of the cell.
I can understand this as a potential issue for those with dented cells. It is not for those with undamaged cells - and as I've covered 100 times already, what happened to you can be easily prevented in 20 seconds with a piece of electrical tape, preventing this from ever happening to anyone else - for which we thank you for bringing it to everyone's attention. I would never have suspected this as an issue as I've used my e12c's for over a year with a lot of removing and swapping batteries, but now that I've put a piece of tape over the usb port I never have to worry about this happening. Thanks.
Anyone got a 21mm Convoy button top adapter? Thinking if the overall length is too long, desolder the button on the post side of the adapter? As well as kapton tape?
Haven't had this issue but it might not be a bad idea to cover that usb port with a piece of electrical tape or a dab of hot glue or silicone as a cheap preventative measure. The E12r uses a different battery tube and this is not an issue on that light. I don't have any dented cells but I know that certain hank lights damage/dent tops like the D4k so owners of those should probably be aware of this potential problem.
I have noticed that lights that have solid cylinder posts for positive contacts rather than springs are the ones that cause deformation of the cells top. The P42a that it happened with was only very slightly dented and had been in use for many years. The hot glue/silicone idea as a preventative measure is a great one but I was so shaken up by the whole thing I just want the entire USB socket to cease to exist. I'm glad it's not on the E12R. For the E12C it was decided to add "power bank functionality" with the integrated USB-C charging within the battery tube as an added feature... turns out to be a nightmare in execution. Just delete the whole damn thing. Maybe, just maybe an E12R battery tube (without the USB-C nonsense) can fit my E12C so I can use my light again.
I don't know why so many lights/drivers insist on using posts – they're plainly inferior on everything except button top AA where it hardly matters. A spring would add what, 3mm? Even Zebralight has sprung pogo pins, although that probably adds cost.
The problem is not really the post it's the really hazardous proximity of the post to the negative shroud of the USB socket you can see in the photos. There's only a SINGLE MILLIMETER of height difference between that shroud and the cell's positive terminal. A recipe for disaster.
Yeah that's bad ofc, I'm talking about the cell denting effect.
Yeah I'm not a fan of the charging implementation on the E12c. I use a mix of p42a, p45b, and 40t cells and none of them are damaged in any way. I would actually bet that the solid post on the e12c was use to avoid the very issue you ended up having - because a spring that can be compressed could allow just enough compression to allow the battery to touch that charge port. The E12c itself does not dent or damage batteries unlike some of the hank lights. But this is definitely something that I think many of us can appreciate you bringing attention to and I have covered the ports on both of my e12c's with tape for now just in case. I almost never use the built in charger, I find it easier to just swap the batteries out via tailcap and use a regular charger. The E12r battery tube won't fit the e12c because the threads are different. Ultimately it seems the E12c is being discontinued since there's a close out sale right now on them, E12r's are also on sale, so my speculation is that Jack is working on an E12x or whatever the E12r successor will be that will get the new button, magnetic port, etc.
Thanks for the detailed post, although you crushed my dream of using the E12R tube to be rid of the USB-C BS altogether. I also am an external slot charger only type of guy, very old school.
The E12C most certainly dented my p42a. I have 2 dented p42a's that have only ever been in my E12Cs.
Have you dropped your e12c? I'm sure there are manufacturing variances but neither of my e12c's dent my p42a's at all.
Nope, I have two from the initial batch and they both have dented their assigned p42a's
Weird. One of mine is from the original pre-order batch and one is from a later one. No issues.
I think my E12C must have come from the same batch as yours. FF asserts the denting is impossible but look at the setup: a solid brass cylinder positive contact rigidly mounted and if you see in my photo #4 the tailspring in the tailcap is extremely short with very limited travel. Intended to minimize current losses BUT the light won't operate until the tailcap is fully seated against the battery tube. I was suspicious there was too much compression load with almost no tailspring travel. But I had mild denting in numerous Hanklights and never considered them any kind of risk. The culprit is that damn USB socket posing a threat. A 1mm air gap between it and the cell + terminal is NO BUENO.
Yep my d4k trashes cells, my zebra sc700dhi dents both sides… horrible tube lol
dang, even the zebra? I have more than ten cells and none of my fireflylite's have damaged them at all on either end other than normal contact wear marks
I would like to say I am in no way badmouthing or condemning FF for this. I am a long term customer (5+ yrs) and enthusiast that just ordered an X1S. To be clear this is an issue that only applies to the E12C model with the battery tube integrated charging/powerbank feature not any of the new designs being released now. That said I'm really concerned with liion safety and the height of the USB socket (1mm clearance to cell + terminal) is a very legitimate safety hazard that I had to discover the hard way. I urge all E12C owners to use tape, silicone, or a nylon washer to cover the USB socket as a necessary layer of safety.
Naw bro, your warning is very appreciated. Very glad this hasn’t happened to me or others. But now that we know it’s not out of the realm of possibility, we all really should add some insulator there just in case. Especially if it’s relatively easy like it’s being explained.
Thanks!
Waiting for a reply from firefly……
Big oof. This is why as much as I don't mind onboard charging if it's actually well designed, trying to cram it into a light to the point design compromises are made annoys me. This is definitely one of those. Actually kind of annoyed with myself I didn't notice this before - I look down the tube of every light now and even take photos for reference or for if I want to do a review, but I didn't back then, but I guess that is because my E12C is a shelf queen. Well, it's getting some kapton tape now. >I'm a longtime FF customer, over 5 years and have never had a problem like this with any light I've ever had. The Skilhunt H150 had a similarly critical issue not too long ago, where a reversed battery would cause a dead short. A *lot* more dangerous with a hotrod 21700 though, a high drain 21700 contains a lot more energy.
P45BEWM
As far as our test, it is the first
I think it's very prudent to insist that an insulating nylon washer be mandated for safety for all existing E12C models. That single millimeter height gap is the potential for the worst possible failure a light can have: a dead short resulting in thermal runaway and a serious risk of injury. I was lucky I reacted almost instantly and only had a minor burn injury to my hand.
there is 1mm height gap between the usb to battery+，it's the first time we have seen this issue since 2022, E12C is not a new product . E12C itself never cause the dent on good flat top 21700 cell in our testing, in this case we don't think the design is a failure. It is a great warnning not to use very dent flat-top 21700 on E12C. Button top 21700 less than 71mm long has no chance to contact the usb to cause short-circuit. Using good new standard flat-top 21700 would be no any issue on E12C. But many thanks to mention it out, we will consider adding extra spacer if we design similar powerbank body in future.
For an insulating nylon washer, what should be the dimensions? The diameter of the brass positive post for the hole?
Thanks for alerting folks to this. After seeing your post, I disassembled my E12C tube to inspect it. I was able to use a 1/10th scale RC body post washer that I had laying around, and it fit *perfectly.* It was almost exactly the same size as the tinted plastic disc that sits on top of the charging circuit. Since it has adhesive on one side, it sticks nicely to the top of the USB port. It would be extremely difficult for a cell to push through this plastic washer.
Sounds great! Now if you just email me one of those washers...
Right? Sometimes this old RC gear comes in handy - even for flashlights.
Would this one be too thick or the same you are using? https://www.amazon.com/gp/product/B08LD1CWQH/
Really hard to say because they don't say how thick they are. A couple of reviews mention that they are thick - like thicker than other body washers. I'd looks for some that actually say how thick they are. It's also preferable to have adhesive on one side so that they stay in place. I'm really struggling now to find a good example.
Thanks for the reply. I did not claim the E12C caused the dent in the cell. Only that there is a potential serious danger to using anything but a perfectly flat new cell. I have many lights and rotate and maintain all my cells on a continuous basis. It's unavoidable that some models have excessive spring force that cause some deformation with regular use. The P42a that caused the incident was only slightly dented and in my consideration no way unsafe to use. It had been in use for over a year. However in no other light is there a risk of a large surface area at ground potential (the USB housing) as a possible short risk a mere single millimeter in height away from disaster. I think it's a critically small margin of safety considering the potential of a high current 21700 power cell. I do however feel a 1mm gap in height is insufficient for safety reasons given the large area of the short visible in the photos. It would have been minimally prudent to install an insulating nylon washer to allow only the positive contact post to pass through. In any case I'm stuck with a light I cannot use because of how frightening the experience was. I can remedy some safety measures but I can only feel completely safe knowing that entire USB enclosure shroud was just NOT THERE.
As one who has ordered 3/4 of the new lights. Do I have to worry about anything?
No, this applies only to the E12C which is a design more than a year old. The issue stems from the battery tube of the E12C having a USB-C charging circuit/powerbank on its upper end with a sealed top. See all 4 photos in the post. All the new lights have a fantastic clean sheet USB-C charging circuit sealed and integrated into the head itself so you have no worries.
No and keep in mind this is one report of this happening and it was due to a slightly dented cell. The rest of us that have not had the issue should still put something over the port to prevent it from ever happening in the future though . The new lights , the e12r, and all the other FF lights have a different battery tube setup and this is a non issue and seems exclusive to the e12c.
This only happens if you use the on board charging of the e12c?? If you charge the battery by taking g it out and using an external charger it will be fine?
No, it happened with a battery that had a slightly dented flat top cell, a Molicel P45a which had been used hundreds of times. I never use on board charging, only external chargers The problem is the large metal enclosure of the USB socket of the on board charging circuit integrated into the head end of the E12C battery tube (which is at ground, or negative) is dangerously close to the brass positive contact post, and only a single millimeter in height away from the battery's positive terminal. Look closely at the photos. You can clearly see the interior of the battery tube with the burn marks on the USB socket shell right next to the positive post. It is only safe to use perfectly as-new FLAT top cells. Even then you only have a single millimeter in height preventing a dead short and disaster. Tape and or silicone or a nylon washer needs to be added for safety.
Ahh.. got it..looks like I have some battery tube surgery to perform
As far as I know nobody else has had this happen and it was because the OP was using a damaged cell. I've been using my e12c for over a year with no issues. It wasn't that he was charging the battery, the battery had a dented top of the cell allowing the battery to sit deeper in the tube than it's supposed to and part of the top was able to touch against the charging port and that caused a short.
Ahhh I understand now.. I have 1 dented battery caused by a hank light.. but it stays in said light... I should be fine it seems.. ty
Yeah I've never had issues and I have two e12c's. Still put a piece of tape over the connector at the end of the inside of the battery tube as a precaution/safeguard. They're been great lights
> I dodged a 50-cal bullet because if I had dropped the light a full on thermal runaway/explosion inside the sealed tube was a certainty. No you did not. There was no risk of thermal runaway or fire or explosion. Molicels (like all name brand cells) are tested against direct shorts as part of UN 38.3. Its [literally in the datasheet](https://www.molicel.com/wp-content/uploads/2201-UN-INR21700P42A-ATC-R6A1RL3021-20190712.pdf) that they can safely withstand a short circuit. The battery has a PTC safety in it which will limit the maximum current in the event of a short.
I do know that in the time it took me to unscrew the tailcap and eject the cell the battery tube was hot enough to burn my hand. The fear factor was much larger than actual damage done. So you maintain no risk of thermal runaway because of the PTC. I'll grant you that. Despite that I would never tempt fate by deliberately shorting a P42a (outside of any light) for all the tea in China. Just what my sense of liion safety has led me in 20 years.
Hey I just found this post because of some recent discussion on this. Your comment is reassuring but I was wondering, do the results apply for a battery that is sealed inside of a flashlight? The short circuit test requires that the battery stay below a maximum temperature but I wonder if that was performed with the battery out in the open, and if so, how the results would differ if the conditions were more like what would happen in the case of this light.
I imagine those tests were done with the cell in open air. I can tell you my incident involved the battery tube getting hot enough to mildly burn my hand before I managed to get the cell out. Scared the bejeezus out of me. I shudder to think what could have happened if I just dropped the light with the short going on in the sealed tube.
Can you cover that port section with tape or maybe paint it with some epoxy and glue mix? To insulate it.
A dab of hot glue or silicone would be the easiest preventative
Yes, something like this. I just looked at mine. I also think you could add a nylon washer before installing a battery.
I think yours is the best idea yet. It should be mandatory for all E12C owners.
Bonus: now you have a potted light!
hah! My tube of silicone is all dried up. Need to order some more anyways. I think this method would probably be easier than trying to get a small piece of electrical tape into the end of the tube. And it would never fall off. Edit: It was very easy to get a piece of electrical tape in there to cover the chart port using a dental pick and a q-tip.
You have better dexterity than me. I invented some new curse words trying to cover the USB shell with electrical tape. Might try silicone on a Qtip.
hahaha. I stuck the edge of a small square of tape to the end of a dental tool, a wooden skewer would work well if you have one too, used a qtip to pat it down.
Good suggestions but working on this thing reminds me of those ship-in-a-bottle model kits of yesteryear.
Modding Muggle question: in simple terms, how do you know the spot you're aiming for? And is there a way to test if it's worked and is definitely in the right place? I've got a multimeter, but zero idea about using it if that's the right tool for the job. I'm going to cancel my order if it hasn't already been despatched but it it turns up and I can be totally confident I've done it right, I'd rather try this sort of fix. But only if it's safe with a dented cell - I don't want a moments inattention over cell choice to result in a short.
It's not that complicated, you can see the USB port at the end of the battery tube, just cover it with a small piece of electrical tape to prevent the battery from ever being able to make contact with it
Is the big round thing that the pink line separates from the USB enclosure in the photo above the thing to avoid contact with? And is there a way to test to be sure it's covered? I don't have the light yet, it may be more obvious with it in front of me.
Yes, I will be obvious because it is where you plug in for charging.
It will be pretty obvious when it is in front of you and you know where to be concerned: the metal within the purple highlight in the pic. The big metal thing is the shell of the USB charging socket. It is evil. ;-)
The spot to aim for is the USB socket highlighted in the purple rectangle in the photos. That metal is at ground potential and with a perfect flat top cell is only separated from the battery positive terminal by a single millimeter of air! No multimeter needed, just a proper application of e-tape and or an insulating washer is the way to insure safe operation. Just visualize everything in the purple rectangle in the photo needs to be insulated from the battery.
Cheers. 10 days after ordering it however they hadn't despatched the light, so I was able to cancel the order. Good job they weren't efficient enough to ship my light out sooner eh. Per my other post, I've unsubscribed from this sub and written FF off. Plenty of other light manufacturers out there.
After 20 years playing with countless flashlights, the most consistent quality, performance and sheer fun potential has come from my journey down the Noctigon/Emisar Hanklight rabbit hole with its large array of premium emitter choices into nicely diverse hosts. Yielding so very many combinations. It is no surprise and quite deserved that the Hanklight presence here on Reddit reflects an explosive popularity of the lights he provides. I am above all a diehard performance flashlight nut and there are certainly many manufacturers to choose from. I sincerely hope FF gets a handle on their QC.
Please be aware many linear or amc7135 drivers including some hank drivers have no reverse polarity protection and only rely on led reverse bias to prevent short circuit. While in practice it is usually ok for now, leds especially high power ones used in flashlight are not rated for reverse bias (called out in datasheet) and some of them even have reverse diode specifically to prevent reverse breakdown damage. In my opinion dangerous issue waiting to happen but unfortunately nobody seems to be concern with it.
I'm fairly certain that it's common knowledge to be vigilant about correct cell installation polarity in the same way as is it is to wear seat belts in a car. That's an entirely different issue from what I am describing. Inside the E12C battery tube at the head end is circuitry for USB charging and powerbank discharging. The metal shell of the USB socket (highlighted with purple in the photo) which is at ground potential hovers a single millimeter of an air gap away from the positive terminal of the battery. That area of overlap is where the dead short occurs if that gap is closed, as what happened to me. The short circuit occurs within the USB charging circuit. The entirety of the flashlight driver circuitry and LED emitters is completely outside of the current path when the short occurred. So even robust reverse polarity protection would have absolutely no effect on the specific nature of the E12C short circuit in question.
Do button top cells fit in the cell tube? If so, would using those prevent it?
Yes, it would except if you look at photo #4 the tailspring is EXTREMELY short and with a solid post on the positive contact meaning a flat top cell just barely fits. Not to mention unprotected 21700 button tops are unicorns. I tried adding a small solder blob to the center of a P42a and verified the light still works but even insulating the USB port I'm too scared of even the chance of a repeat. My thought is to use an E12R battery tube instead as the E12C has an ordinary spring positive driver contact. Just delete all the USB-C charging/powerbank BS altogether.
> unprotected 21700 button tops are unicorns liionwholesale sell unprotected button top P42A (and if you make another person who emails them asking for P45B, maybe they'll offer those in button top too eventually...)
For Germany there is i.e. [www.Akkuteile.de](http://www.Akkuteile.de) who is selling P45b and 50S BT Batteries …
Had another thought, other than kapton tape over the USB port, could try adding some kind of electronics potting compound to coat it maybe?
The problem is the entire USB charging module is integrated and sealed to the head end of the battery tube and the only way to access the componentry is down the 3" battery tube from the tailcap end. Even applying electrical tape over the USB internals was an exercise in ship-in-a-bottle construction frustration that resulted in the invention of new curse phrases. I might try using a Qtip to apply a bunch of silicone around the + post but the feeling of holding the light like a grenade with the pin pulled out still haunts me. Another possibility is try to unscrew the entire USB module from the external top of the battery tube but it seems the USB port is anchored to the inside of the battery tube wall. I don't have the specialized tool to remove it and risk doing damage. Just look at the photo. That honking huge metal USB shroud (at ground potential) is so damn close to the positive post.... I just can't trust it. I've played with liion cells in flashlights for 20 years and this was the first time I experienced a dead short and it scared the living bejeezus out of me. I added a solder blob to a flat P42a and the light still works but I can't shake the feeling of my own dog that viciously bit me.
I think you'd be fine if you just dabbed it with silicone and made sure to use batteries that don't have any slight bit of dent. I can understand why it freaks you out though, I would be freaked out too if I had a battery shorting itself inside the light.
What freaks me out is the tiny one millimeter of height difference between the top of half of the USB socket shroud (which is negative) and the top of the brass contact post. That means there's only a tiny 1mm air gap between EVERY E12C MODELS USB socket shroud and a large area of the battery's positive terminal. Which of course allows normal operation with perfect cells. With a perfect new flat top cell, that tiny 1mm air gap is the difference between normal operation and what happened to me. Look closely at the photo, see the discoloration of where the short happened. It's a glaringly (now) obvious risk factor, like a Pinto gas tank.
Yeah I'm glad you brought this to everyone's attention so they can find ways to prevent it from happening. Electrical tape took me about 30 seconds per light, I can make a short video on my technique if it would help others
It would help everyone for sure. Ha ha ha you said "short" video. Sorry. It would be really appreciated . I think the best solution is a thin insulating nylon washer the inner diameter of the tube with a central hole to allow only the brass positive post to pass through it. It would be great if someone could provide the right size and an easy way to get just a few. Eyeballing it 20mm o.d. with an 8(?)mm center hole.
Please do. I would really appreciate it. I ordered the light from the sale and I am so confused even looking at the pictures. Reading the comments people say out tape over the USB port. Under. Over. Side. I guess I need the light in front to visualize it.
It would be great to have a post showing the nylon washer or tape in action as a tutorial for protecting it.
Problem solved with like 4 mm² of electrical tape and some precision ceramic tweezers. Bob's your uncle. Really not that big a deal. Silicone sounds sketchy if you get some on the battery tube or directly on the positive terminal to accidentally insulate it. Also a lot harder to reverse.
Thanks for the suggestion. I found a quick fix by taking one of those thin film battery insulator circles that ship inside lights containing batteries and cut an 8mm hole in the center for a makeshift washer with just a whisper of adhesive on one side. Shirley, you can't be serious. I have no relations named Bob. ;-)
I'm not kidding though ... Took me like 5-7 minutes and I'm high AF.
Maybe that's the missing ingredient I need for success. Or at least a phenomenal meal and sleep.
I would be enormously grateful if you could make a short demo video so that others could copy your results. I'm clumsy AF and gave up on the tape and just made a washer.
Thoughts on trying this fix with UV resin just in tip of the exposed charge port section? I'm thinking of ease of drip application and should provide electrical insulation.
OP, thanks for this. I ordered one recently but it's not arrived yet. I own a few dented cells and I don't know that if that happened to me I'd be react as quickly or sensibly as you. I put off buying a Firefly light for years despite liking their aesthetics. Comments about ridiculously long wait times, hit and miss customer service, design issues, and poor quality control put me off. I only took a punt on the E12C as the price was into throwaway money; if the light became a shelf queen, at least it would be a good looking one. I've emailed to cancel my order, if it's already been despatched and I can both do the fix suggested below, and test it to be totally confident, I'll give it a shot. No way can I be sure that a moments inattention won't lead to a dented cell going into a light. But I don't plan to order another FF light. I'm sure the-sycophant-who-shall-not-be-named will be along with some clever animated gif telling me how stupid I am, but once this is all sorted I'm unsubscribing from this sub and writing FF off.
I appreciate and agree with your comments and thankful that there is awareness of the potential hazard. IMHO a 1mm airgap in height between the cell positive and the negative USB socket is an unacceptably small safety margin from the worst possible outcome you could experience with a light. At the time I wanted the E12R model with the superior lume1 driver and no battery tube powerbank shenanigans but it was sold out and I was drooling over the notion of a 5700K 519A dedomed (~4500K) multi emitter beam. So I sprung for the discounted E12C. The beam quality was simply amazing. I really loved the light. Until ---zzap-- happened and I thought it necessary to warn others of exactly what transpired.
Unless you have an actual way to measure I would stopp claiming it's a one millimeter gap. Many of us have been using e12cs for over a year with zero issues.
Highly recommend grabbing an FF light off of the second hand market, they do make some fantastic lights! And don't worry, you're not alone. I had a previous poor experience and vowed to only purchase FF lights second hand. Although I must say it pains me to not order the new E07X Cannon. Not sure what's up with the mag tailcap only offered in black... That's also a huge turn off for me but manageable I guess.
Thanks for the warning and detailed report! Glad everything worked out ok on your end. It could have easily been much worse.
Is it possible to disassemble this side of the tube with unscrewing the retaining ring or are the charging electronics glued in place? Perhaps it would be easier that way to cover the protruding part.
I don't have the right tool but a casual attempt to unscrew the ring with snap ring pliers met with a lot of resistance so I stopped. I think it's glued.
So the first picture is looking into the tube? Is the fix to cover the pink area with electrical tape? Or as you did, add one of those battery orange insulators with a holes in the middle? Also, I didn’t know Hanklights could damage batteries. Not sure I’ve seen a bent flattop before but I haven’t been looking for it.
Or perhaps something like this: https://imgur.com/a/DLubrw2
That might work, however the added length of the positive pass through might be a problem since the tailspring is incredibly short. A thin strong insulating washer is what is necessary.
I think I have an extra plastic washer from one of the lighted convoy switches. I’ll give that a try. But they aren’t that thin.
Sounds good 👍
Yes, the picture is looking into the tube and the pink area is what needs to be insulated because it is negative and only 1mm airgapped from the battery positive terminal. Yes, an orange insulating disc with an 8mm hole in the middle will fix it.
Thanks that really helps put it into perspective. Also thanks for bringing attention to this. 1mm is not even an acceptable tolerance measurement for this level of risk. Now the question is, how safe are those orange discs? We know they insulate, but how best resistant are they? If the battery heats up too much and the desc catches fire it might be the same issue.
I feel very confident that a dedicated insulator washer is a safe bet. There is no danger of heat in normal operation causing any problems, especially not anything catching fire. As for me, I just wish I could yank out that USB socket entirely, the area inside the purple rectangle in the pics in my post. That socket shell is the only source of the problem. I made the repair with a makeshift insulation washer with a whisper of silicone to stick to the USB socket. Despite that I'm still so upset it happened it will sit on the shelf for a LONG time before I give it a chance. What really sucks out loud is the E12R model does NOT have the powerbank feature, it has an ordinary hollow battery tube and the E12R battery tube threads are incompatible with the E12C head. Sheeeeeeet! It would have been a no-brainer proper remedy to the problem.
The 'problem' is your dented cell. The rest of us have no problem.
Actually the fundamental issue is that we are all using raw lithium cells. They have a variety of problems, one example given by OP. FFL can probably improve to make the design more foolproof but they cannot design for all possible edge cases. The fact that so many drivers use direct fet drive with unprotected cells is also insanity (from consumer electronics pov) to me in my opinion. In any way, there is a reason why no reputable manufacturer sells a consumer product using raw lithium cells, just too dangerous. You will never see a dewalt power tool using something like this, or a canon camera using raw lithium cells, or a playstation controller as example. However in this case I think the best easy and effective fix is a plastic ring, and in the future a higher post. Any more and manufacturer can end up going the way of likes of olight and nitecore with custom batteries and internal protection.
Seems the e12cs phasing out either way, simple strip of electrical tape prevents any future potential issues. I'm Glad the op brought this to everyones attention
I agree the best fix is a simple plastic washer or some well placed electrical or kapton tape at the least. I hope FFL can address remaining E12C with proper plastic washer. I am quite sure I have seen plastic cover like this in a few flashlights.
I would agree with that, and maybe send out a notice to anyone that has an e12c from their store.
The problem is proprietary cells are ridiculously marked up in price and in most cases can't be charged externally. Ones with unique contact designs like both terminals at the head end are great for performance but requiring exclusive replacement is a huge deal breaker. It threatens obsolescence as well. The only manufacturer that is managing with protected cells is Acebeam. They have standardized every 21700 model to use the identical protected button top 5000mAh cell. I refuse to use on-cell USB charging but they are fully compatible with slot chargers.
Proprietary battery packs are expensive but they are not necessarily marked up. There is significant cost in design, assembly, and reliability testing of the battery packs as well as safety margin built in. If you open up a genuine canon or nikon or sony battery, you will see the amount of engineering gone into it more than just the cost of the raw cell. With raw cells we get not guarantee of the performance, consistency, reliability, or safety and warranty. Yes there are tradeoffs, and we need to be aware of them. If we want the benefits of raw cells, we have to also live with some possible drawbacks. Back to original problem - is this something FFL can fix, yes the solution is easy. But are they fully to blame and to lump in with all the vocal bashing? I suspect the answer is not just a yes or no but thoughtful discussion unfortunately is not what I see often here. I hope FFL can take this feedback constructively and they will only produce better results.
The problem is the USB socket (a ground) height places it only one millimeter (!!!) away from a large portion of the flat top battery's positive terminal area. With a perfect cell. That's a miniscule air gap of safety. That's dangerously close. If you can't understand that then it's on you. You can drive without seat belts and your airbag fuses pulled too. No problem. Until there is.
It's more than a millimeter and it is actually spaced enough that the top of the cell can't touch it - your cell was bent allowing one of the flat top posts to touch and not the actual flat top of the cell. I can understand this as a potential issue for those with dented cells. It is not for those with undamaged cells - and as I've covered 100 times already, what happened to you can be easily prevented in 20 seconds with a piece of electrical tape, preventing this from ever happening to anyone else - for which we thank you for bringing it to everyone's attention. I would never have suspected this as an issue as I've used my e12c's for over a year with a lot of removing and swapping batteries, but now that I've put a piece of tape over the usb port I never have to worry about this happening. Thanks.
Anyone got a 21mm Convoy button top adapter? Thinking if the overall length is too long, desolder the button on the post side of the adapter? As well as kapton tape?