Got my q8 plus with flat tops. Sofirn confirmed the button tops were replaced earlier this month. Implying if you order the q8 plus and select 21700s going forward you will receive flat top 5000mah sofirn cells. They arent the Lishen lr2170sd’s 5000mahs though, with the triangular positive terminal. At least not in my case. These ones handle higher current better than the other 5000mah 21700s and they look the same and weigh the same and have the same dimensions as the 4000mah sofirn 21700s. But I haven’t capacity tested them.
These do work in the Q8. The flattop does sit slightly proud like a Molicel, but not quite as proud. The wrap holding down the insulator ring, on mine anyways, drags around the brass contact when screwing the head down. I’ve already had to rewrap a cell after assembling the light only twice. The insulator ring is solid though, and the damage was just superficial, just a quick rewrap.
Pictures of the cell unwrapped here and the cells in the light as shipped below.
Talking with sofirn about this now. They’ve said not to worry. And again the light DOES work with these. But I’m concerned the terminal isn’t quite as raised as it needs to be for this application and repeated assembly and disassembly could cause a short. Voiced those concerns and waiting to hear back.
Thoughts? I’m all for better performing cells, and these were perfectly matched up when they arrived btw, I just don’t think the top is raised high enough.
They might be the BAK N21700CG, a 5000mAh 15A battery that’s been used by Sofirn before, though the edges of the positive-terminal posts are slightly different.
Another alternative could be EVE, they have a 5000mAh 15A model as well but I haven’t found photos.
The claimed “50A” current rating is very interesting, doubt they’ll actually be anywhere close to it but I have to wonder what is actually inside them; if it lives up to capacity and has a decent max current (between 15-20A) they could be a good way to get a bit more power into a 1x21700 light without the cost of 50S or P45B.
Oh ya that 50a rating is just a number I’d hope that nobody believes that.
Markings like print? No I’ve never seen print on any sofirn battery. Did have these weird white lines on the bottom 1/3 of the case tho. One ring and 4 lines going down from it. I assume just something from manufacturing. Never seen it before, don’t think it means anything. I’m assuming that’s not what you meant but I took a picture of it so here ya go
Looks like a sub optimal combination there, although I’m surprised you had to re-wrap the cell. Why did you have to re-wrap the cell? What was the extent of the damage caused by the wrapper dragging on the brass?
I fail to see how a short could be caused by the situation though, even if the wrapper were removed. Did you test for continuity between the can of the cell and the top rim of the cell? When I’ve tested this on other cells, I found that the top rim was still battery negative. (cathode) I’ve seen it claimed countless times to the contrary, that the top rim will short to the can, but that doesn’t make it true.
I would like to see the unwrapped cell picture but imgur is trash and won’t load the photo for me on any of three different browsers and without any add-ons enabled. I recommend imgbox for image hosting, you just have to link to the image directly rather than the landing page. Or use BLF to host the photo. Edit: I think you just uploaded the picture in the previous post. Thanks.
Sofirn is presumably presenting… “optimistic” numbers for this cell. Even the P45B doesn’t produce 50A and 5000mAh, and P45B isn’t just some freebie cell included with every Sofirn light.
I should’ve taken a picture. It was a sharp cut like somebody nicked it an xacto knife across the wrap at the top where it closes over the insulator ring. Probably from the edge of that brass ring. You can see on the tops of the cells lines from where it’s making contact with that brass ring as the head is being twisted down. So the ring and the wrap above it is being pushed against that brass ring with some decent pressure while the head is still screwing down. I didn’t expect anything to happen so quickly, I was thinking more like, do that 100 times and eventually it would cut through.
Yes, this will always be negative.
Its not that. It’s how the positive connection on these sofirn soda can lights work that would cause it. It’s a unique set up if you haven’t seen it before.
See the brass ring on the right, above the battery? That’s the positive contact for all 3 cells. A solid continuous ring. If the insulator was damaged, and it’s a flat top, the negative rim at the top of the cell could contact that brass ring at the same time as the positive. It’s a piece of brass going straight across the terminals. That’s mostly why these used to come with button tops. But people found they can work fine with raised flat top like a Molicel or a Sanyo 18650. That’s what sofirn is trying to do here. My concern is these don’t have a positive terminal that’s raised high enough.
Edit: here’s the other pictures that were on imgur
So for the short to occur, there would need to be no wrapper OR paper insulator, and because the positive contact does protrude quite a bit beyond the cell casing, the positive contact would also need to be crushed to a significant degree before the short could possibly occur.
Well no, not no wrapper or insulator, just one that’s worn down from being dragged around the brass ring a bunch of times.
So those two pieces don’t push together, you screw them together. And it’s takes two hands, it’s a decent amount of pressure pushing that ring down on the tops of the cells. And it takes a few turns. So while that brass ring is pushing down on the cells, it’s rotating. And it is making contact with the casing, you can see it on the wrap (not in those pictures, those were taken before the flashlight had been assembled) and that’s presumably how the one got cut. So that brass ring is pushing down on the cells while it twists on and off. You can imagine how if you do that 100 times, metal sliding against metal with a piece of paper in between them, that its possible it could slice through.
Just to add- yes, if there was enough distance between the top of that positive terminal and the rim of the case there’s no issue. On this particular battery there’s really not much distance. And at certain angles there isn’t any, it’s not that uniform. If you look at my thumb there holding the battery, how much does that flat top stick out? I can’t measure it. Half a mm? When the wrap is on it looks flush.
Seeing how there is a physical gap of .5mm or whatever between the casing and the positive contact in the axial direction, a short seems unlikely unless the positive contact were significantly crushed.
Ok. I understand your point. That’s fair. I was just trying to give you all the information.
Half a mm is cutting it kinda close for me. Flashlights do get bumped around from time to time. Terminals do get dented. Wear might be overlooked. Maybe someone not aware of any risk, maybe they keeps this light in a backpack or maybe assumes the negative is all the way on the opposite end of the battery and aren’t checking for or concerned about wear might get into some trouble. It’s certainly plausible. There’s a reason afterall that these soda can lights typically require either button tops or some sort of adapter or cell holder.
For years sofirn said not to use flat tops with this flashlight and now they’re packaging it with some. Just something to be aware of if you get one. It actually still says on their website that button tops need to be used with this light so
Yea I wouldn’t want to use a cell without any barrier on the can. I’d probably make one out of Kapton tape or cut one out of adhesive backed paper like shipping label printer paper, then re-wrap.
Thanks for sharing and explaining the situation in detail.
I have found THE biggest issue with lights bearing that brass donut positive contact is a user that doesn’t pay attention and drops one cell in backwards.
Snug the battery tube down, don’t crank it til it simply won’t tighten anymore. I’ve seen a user put a wrong length cell in and destroy it cranking down on the threads insisting it will fit.
While it seems pretty straightforward a certain amount of common sense is a must. Or magic smoke…
As far as everyday banging around… that’s what springs are for.
I’m just saying a gentle snug is sufficient. No need to torque the tube down. On occasion a long cell can compress a spring and turn it into a solid, cranking the tube down uses threads as leverage and crushes a cell which could possibly cause the short you were worried about. A wire bypass in a spring, done wrong, could stack a spring and cause the scenario where the cell gets crushed.
So, just saying, overtightening the tube is unnecessary and potentially dangerous.
I’ve had the positive terminal on a LiitoKala 21700 battery flattened considerably from swapping it from flashlights to a charger. It probably didn’t help that 21700’s are a tight fit in that charger (but other brands of 21700’s haven’t had the same happen.)
Perhaps Sofirn aren’t concerned as they think people will leave them fitted in the flashlight and use the built in charging?
Oh ya I don’t go further than when the circuit is completed and the light flashes. I don’t think I could if I wanted to anyways. Not without a vise and a pipe wrench…could maybe get an big impact socket around it actually with the way the cooling fins are spaced out…
I don’t have any liitokala 21700s but if it’s anything like the 5000mah sofirn/wurkoss lr2170sd rewraps with the triangular positive terminal, every single one of those I have is at least slightly dented. The flat top on those just seems really thin and weak, and the cell is a couple mm too tall. Also theyre always packaged in lights with a brass button on the driver. Theyre dented right out of the box sometimes. I wonder if that intentional. Make the positive cap weaker so the vent at at the other end doesnt get crushed instead
Does anyone know if the single 21700 adapters would work with the Q8 Plus battery tube or does the cell molding not go up high enough to prevent these from sliding around?
