In 2016, I purchased 8 protected KeepPower 3500mAh P1835J 18650 batteries. All fit in my Zebralight H600Fc Mk III at the time of purchase.
Over years of periodic (and sometimes frequent) use, all but one has swollen to the point that they no longer fit into this light — girth-wise. Another only just fits after I removed the label. One cell did this over the span of about three months and lodged itself firmly inside the Zebralight — meaning I had to epoxy a piece of wire to the bottom of the cell to extract it.
What would you do with these cells? Two are still usable in the Zebralight (which is the light I use daily at this point), but I’m not sure how much I trust them anymore. Surprisingly, all cells still charge to 3375mAh+.
Strangely enough, four protected Sanyo NCR18650GA that I purchased around the same time have none of these issues. I believe these two products use the same base cell, so the issue appears to be either with KeepPower’s protection circuit or that they were using lower quality cells.
Has anyone also experienced this? Needless to say these will be the last KeepPower products I purchase.
Thanks for the replies. I figured that’d be the response, it just seems like a shame to get rid of them – especially since their relative price and reviews made them seem like a premium option. Regardless, I’ll drop them off at a recycling place tomorrow.
The concerning thing is that, even after unwrapping them, there are no obvious signs they’re swollen and the cells look entirely uniform. They also still fit every other light perfectly fine, so if I didn’t have the ZL I’d have no idea there was any issue.
I have never heard of swelling cylindrical cells, this is very strange. Try measuring diameter with calipers, so you can see if it is uniform or not, if it is stronger in the center, or if maybe they have been slightly deformed to be elliptical instead of circular in cross-section.
They are defective and dangerous and maybe the next time you charge them they could go up in flames and burn down your flat/house and kill you in your sleep. Really not worth saving a few bucks.
Discharge them in a flashlight at a low to medium setting and discard.
Swelling == pressure build up. Keep charging them to the brim and it will rupture, vent with nasty chemicals or even flame. 8 years old cell is old enough to be disposed of.
A battery/cell is all about chemical reactions. And even if you don’t use it (al lot) there will be some deteriorating over time. Some deteriorate faster, some slower, but all batteries “die” eventually.
This one is so nice to warn you about what is going to happen. Don’t ignore it. Don’t even try to revive it. Dispose of it a.s.a.p.
A faulty alkaleak may ruin your light and your day, a faulty lithium cell may ruin your light and your life.
Good point. I checked and you’re right about them being slightly elliptical; they vary by about 0.6mm (with labels removed). However, the unwrapped cell seems to be close to completely circular and the widest point on each cell is at the nickel belt that connects the PCB to the positive terminal, which is contributing to the asymmetry at least somewhat. It’s difficult to tell if it’s the only cause considering the very minimal margins. Each cross section is also at least 18.6mm so I’m not certain they’d fit comfortably if they were perfectly round.
Not about the money, they’re of little use to me anyway (and I’ve switched to unprotected cells) so I would’ve just put them up for free in case someone else could put them to use if they were safe. It more just seems like a waste of resources. But in any case, I already said I’d recycle them.
Possible, but the ZL is able to use cells up to 69mm and the spec sheet for these cells show 68mm, so I’d expect to hear more cases if the light caused this. It doesn’t feel like a lot of torque’s required to screw down the tailcap either (and nothing in comparison to my Emisar DW4). It also wouldn’t explain why one of the cells is completely fine (which has probably seen the most use by this point) and why the Sanyos aren’t affected.
They were charged with an Xtar VC4, usually at 500mAh. I also stored them at 3.7V except for the cell in the light.
Well yes, obviously they’re wide. But that isn’t the issue since they all fit when new; there’s been a change over time. Also the protected Sanyo NCR18650GAs are double wrapped and look to have the same nickel strip yet fit without issue.
There’s no corrosion on the cell I stripped. I’m wondering if the adhesive on the black wrap has absorbed moisture and expanded over time.
Bingo. What matters is the Delta thing - the change over time, not the absolute measurements at any given point. Your light is essentially a ‘go / no-go’ gauge in this case, and if the cells used to pass that test and later do not, it’s the change that matters, and the possible reason for it. Whether the overall package is perfectly cylindrical may be interesting, but not particularly relevant - unless perhaps the cell housing has a seam, and that has exposed the pressure induced(?)‘swelling’ more at that point. I can’t think of a reason for swelling that I wouldn’t consider to be bad.
You also have a control’ in your experiment, which in this case is several other comparable cells which have not evidenced the problem. This suggests that the variable is the specific (type of) cells.
I’m not sure you’re getting closer to ‘root cause’ on this, and I’m not sure you can, but I don’t discount the significance of it, and would certainly like to know the root cause; I just don’t know how to get there.
