For as long as I’ve EDC’d 18650 lights, I’ve actually used them everyday as well. This means I’ve dropped them dozens - maybe hundreds - of times. Besides the inconvenience of retrieving a light, and the slightly worse side effect of it acquiring battle scars, there’s actually a real safety and reliability concern which is indenting the cell. Over the years I’ve retired many of not-cheap 18650s after such falls/impacts that leave anything but the most minor of deformations, especially on the “-” end of the can. As the years went on, our quest for ever lower resistance and crowded, double-sided drivers have yielded stiffer, narrower, and less forgiving springs and lights that only accept unprotected flat-top cells, exacerbating the issue.
One solution: Install snug-fitting o-rings inside both ends of the battery tube . Right now, my EDC is usually the FW1A. I’ve acquired 14mm ID x 2.5mm thick metric o-rings (McMaster Carr) for this application which minimized axial movement of the cell. The tail o-ring is never removed, but the other has to be handled every time a battery change is needed. I’ve considered gluing a few to the front of some cells, and modding a charger bay to accommodate, but this seemed like an over-complication.
I did some drop testing with these installed from a height of up to ~1m onto plywood in both worst-case orientations with a dead (0 Volts) HG2 … No dents on either end. Light functions 100% normally with them installed, and assembly is not much of a fuss IMO.
Very simple mod that I will probably do to every light from now on, especially with larger cells e.g. 21700/26650/etc. Also something that could be given consideration in future BLF designs.
Really, did not know that. Is there a link to teach us what damage is acceptable and what prescribes replacement? Today, I would discard any battery with a significant dent, especially if I carry the light in my front pocket. What’s five dollars compared to an accident of some sort…oh my, oh my.
Grab a C clamp, and stick a BB on the positive end. Squeeze it, and smash the positive end in to see if anything happens. Let us know what you find out.
I’ve got 2 flat tops that are rotated in and out of the FW1A and one of them is dented on both ends. I wasn’t too sure how it happened but I have dropped it a few times. I wasn’t overly concerned with the minor dents but I may experiment with o-rings.
My Sc600 MK3 Hi dents up the positive end of the cell if I drop it. The pogo pins aren’t forgiving like springs are. My older Zebralight’s , with springs, have never damaged a cell.
I have two Sanyo GA’s that can’t be used anymore, because they are effectively too short to
maintain contact, on both ends if the light is bumped or moved quickly. The light turns off with any kind of quick movement. This is because the positive
end of the cell is pushed in too far.
Anyone know of a good way to remedy this on a light with pogo pins, and a one piece body?
Or a way to pull the positive end back into place?
Magnets can shift and cause a short which would be a bad thing. Solder blobs only take a minute or so to add and I’ve never had any issues with them coming off.
First off I’m going to say that I’m not a safety freak or in general paranoid about potentially dangerous things in my environment. I do however eliminate or avoid unnecessary risk, and while not cheap at 5-10USD/cell, this is still trivial compared to the cost of an incident. It’s also relevant to note that I’m not a newb when it comes to electrochemistry, mechanics, and the safety considerations in the design of a modern cylindrical cell. In fact, I’ve worked as a researcher and engineer in secondary (rechargeable) batteries for most of my career.
As for the at home abuse testing of a charged 18650, I would generally recommend not to try it without more appropriate equipment, but to each their own. I’ve had cells do unexpected things in the lab before, and have heard of many stories from respected colleagues; enough to respect them at least. Glad to see your test ended without any drama.
I think the larger picture of this design consideration is being overshadowed with the debate of the intensity of the risk that it nearly eliminates. For next to zero cost, we could avoid any cell damage - which by the way, can cause contact issues in lights and especially on some chargers.
As for repair of dented cells with solder… I’ve done it successfully before on both ends of cells. Getting the negative end hot enough though for the solder to wet out is something to be careful with. A powerful and hot iron should be used with good flux. I also quench the bottom of the cell on a wet sponge immediately afterwards. This is another thing that I won’t advocate the practice of to an audience of varying skill levels and comprehension of risks, but it surely is an option.
I wouldn’t do it without any hand and eye protection….but it’s an interesting vid, thank you. It seems cells can handle quite a lot of abuse and that denting is unwanted damage but not a safety risk, at least with a good cell.
I did a follow-up video, with some more “aggressive denting” (i.e., with a sledge hammer).
In summary, it’s really difficult to get a Samsung 30Q to explode or catch fire, even with serious physical abuse. I think you have to puncture the cells to cause them to flame.
