I have a couple of lights which don’t support protected cell batteries due to the tube length. The extra length of the cell, caused by the protection PCB prevents the un-anodized end of the tube from making electrical contact with either the tail cap or head, effectively physically locking out the light.
I’ve heard others talk about this but haven’t seen a dedicated post so here’s how I fixed mine. Click on the pics for full size versions.
First, I took a small paperclip and straightened it out as best as I could. Then I took a pair of pliers and did my best to wrap the paperclip around an old dead primary battery. Sort of like making a spring or wire wrapping.
I then cut a section of the coil, less than a 360 degree full coil. Next, I flattened the coil as best as I could, then inserted the coil into the tail cap of my light so that it sat in the corner formed by the flat base and cylinder wall. If your light has a tail switch, you’ll want to avoid touching the spring with your paper clip, as this will effectively bypass your switch, leaving the light constantly on.
The extra thickness of the paperclip closes the gap created by the longer battery. Voila! My Manker T01 and UTorch UT01 now work with protected cell batteries.
A couple of thoughts:
I think it would be better to do this to the tailcap side as opposed to the head. Someone mentioned horror stories about the paperclip coming loose, getting caught in the threads, rendering the light un-openable from that side. I think it’s probably easier and cheaper to get a replacement tube and tail cap than a head and tube. Also, while batteries are typically wrapped in some sort of dielectric (ie. heat shrink), without that wrap, in most batteries, the entire body (except for the tiny positive terminal) is connected to the negative terminal. If the paperclip were to work loose, I could see it puncturing the wrap and shorting the two poles. On the base of the battery, pretty much everything is negative, so less chance for a short.
I’d probably limit the size of my coil section to less than a full coil. It might be possible to stack more coils to allow using longer batteries, however you then run the risk of the coils collapsing in. If your gap is too big, I suggest a thicker paperclip or heavier gauge wire. But even that has issues because if your wire is too thick, the tube could end up pushing it towards the center of the tailcap. Would be nice if I had some square wire…. Oh well.
Considering the low power and relatively large contact area, I’d be curious to know how significant any losses would be. Still, the copper would be a lot easier to form and bend.
Never though of using snap rings, but, sure, why not? These are actually designed to fit into an internal grove in a tube in order to hold something captive, like a cylinder, lens or something else that you don’t want sliding out of your tube. If you had one of the proper size, though, should work. These are generally made of spring steel. I’m not a steel expert, but my understanding is that spring steel is usually pretty brittle and, well, springy. Again, Lexel’s concerns about conductivity should be considered.
Bet you could find those at your local machine shop or hardware store.
The dark color on steel springs is often a thin layer of oxide. Oxides do not conduct electricity. Of course, it’s a very thin layer and I have no idea as to the dielectric strength.
I think if you drill a small hole in a dowel, you can use that to hold the end of the paper clip, then wrap it around the dowel with a pair of pliers. Maybe a copper pipe would work better. For that matter, if you could find a piece of copper pipe or tubing, you could hack saw off a very short piece and use that instead.
Wow…1/2” copper pipe is almost perfect. I’ll upload pics later… Might have to cut the pipe and open it up a bit. Might work out perfect as is. Bummer, my tubing cutter is at home.
What to you think about using sterling silver wire? It’s pretty easy to come by (jewelry supplies), should conduct very well, easily malleable, and resistant to tarnishing. Also would be fairly easy to flatten and not very expensive. I think typical sterling silver is around 92% silver, with the rest being made up of copper and other metals.
