Some lights use magnets in their caps. If they don’t, there are sometimes replacement caps with magnets available. I wonder if somebody attempted just adding a magnet to the cap?
For 18650/18350 lights I imagine that could be a cylindrical 18×3 (or 2) mm glued to a bottom? Would the spring hold with it? Would this be strong enough? Leave enough room for battery? Have any other issue?
I think the rating is the most important thing.
I wonder, all other things such as shape/distance being equal, how much practical difference in ‘sticking force’ the differences in the grades represent?
It appears that all other things being equal (geometry, size, air gap, surface, material that the magnet is attached to etc.), the following may be a good approximation:
Convoy sells them for select models. N52 magnet ring D20*16*5mm - Convoy flashlight
I have added magnets under the spring on several lights, I use the N52 grade magnets. They usually work fine.
You need to do some measuring to make sure the magnet will fit inside the spring and there is still enough clearance for the spring travel so it will not damage the driver or cell. Of course you need to make sure the magnet is strong enough through the tail cap to hold it the way you need it held. But it is doable with a bit of experimentation.
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If the light has a spring at the head, you can simply replace the tail end spring with the magnet, if both won’t fit, or you cant get contacts to work. Just have to make sure of good contact from cell to cap to body tube, or cell to body tube directly.
On my lights with custom 3D printed plastic tail caps I have a 2mmx6mm magnet on the cell, sitting on a metal disk(USA penny or nickel) that contacts the body tube, and a Big 4x16 or similar magnet in the tail cap behind the copper. On some I have plastic shims between metal disc and big magnet to take up play, and/or insulate the rear magnet from current.
Same can be done with aluminum caps, leave out the metal disc or stack it up to take up slack.
Care must be taken to not over compress the springs, or have too thick of stack at the tail etc, you CAN hurt drivers and crush in the end of cells.
This Can be done with no springs, but I really advise against it… half a mm difference in cells or the shims/magnets can crush things, or make the light sporadically not opperate. Usecl at least one spring if at all possible!!
Strong grade magnets , N52 if possible are a must, and thin as possible between magnetic and the outside of the cap. 1.5mm of plastic at the tail works good, but 2mm can start to interfere…
Shouldn’t matter as much with aluminum caps, they’re all pretty Thin at the back, but a cap not designed for a magnet will probably be thicker than one for it…
If at all possible putting the magnet outside the light is the best, no strength interference. But then some lower quality magnets are brittle too, depending what you do they could be chipped or shattered if dropped.
I’ll second the recommendation of kjmagnetics.com, I’ve been using them for close to 20 years( that sound wrong but probably isn’t… 15 years at least), always been quality, and good prices/ service, and selection.
Oh yeah, forgot, I have also seen guys cut and shorten springs too, but that was too fiddly for me, and I wanted everything reversible if I needed the stock setup to work.
Heck, you can even buy different (maybe even shorter )springs too if you dig around (aliexpress if you want to take the chance) even taller if you ever needed it… I’ve seen guys stack/nest 2 springs to take up space in a cell.
Guess I should note that technically any spring change or like I do replacement does change electrical resistance in the circuit… I’ve yet to notice any problems with that. But it is possible.
