Tidying the garage and came across this simple 3 cell 18650 holder I made last autumn for a commuter light. Thought it might inspire others to take the concept and improve it.
It's made from a length of 22mm plastic plumbing pipe from B&Q, which has an ID of 19mm, perfect for 18650's. The end caps are (I think) from domestic radiator lockshield valves. Anyway, they are a snug fit over the pipe and, with a generous amount of pvc solvent weld, I can't see them coming off.
The -ve terminal is a spring cut from an AA cell holder, glued to the bottom of the end cap and soldered to a wire that runs outside the tube, back up to the +ve. The +ve terminal is just a copper 'button' soldered to the wire and glued in place.
The only thing that needs care is cutting the access hole in the right place, so that the first cell goes up the tube to the +ve terminal, the second drops to the bottom and you can then push it down against the spring tension to pop the third cell in the middle. If you get it right, everything sits as snug as a bug in a rug.
The 'door' is another piece of plastic pipe cut and sprung over the main tube. I warmed it with a hot air gun to stretch it a bit so it wasn't too tight. The ugly black tape is only there to keep the external wire against the tube and to provide some degree of strain relief. Bit crude and I always intended to tidy it up before sharing here.
Here's the complete thing:
Mounting to the bike couldn't be easier. I just bolted a pair of 22mm plastic pipe clips to the bottle bosses on the frame.
And in situ:
As I said, this was just a 'proof of concept' and rather cruder than I would have liked. For example I made no attempt at waterproofing and I'm not convinced the strain relief is adequate. I didn't like the 'loose' external cable either.
I did make a start on MK2 which was to have been a 4 cell version but I have yet to finish it. My plan for Mk2 was to use a 22mm copper end cap to which I soldered a spring (extracted from the battery holder of a defunct radio) and a length of solid copper cable (the earth wire from a length of 3-core mains cable). I planned to stick the end cap in place with silicone.
I grooved the plastic tube with the trusty Dremmel for the wire to run up, and bought some white insulating tape to hold it down more neatly.
As a battery holder it works very well and I hope this provides inspiration for someone to come up with an improved version.
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Thread: Quick and easy DIY 18650 holder