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Not an electrical engineer, just a hobbyist. But thought this might be the best place to come with my question.

I bought a bike light that uses a single 18650 cell for power, thinking it would work with standard cells. Little did I know, they use a different 18650 configuration than I'm used to. It has concentric positive and negative terminals on the one end, with a non-conductive material on the other side of the wrap. Other than that, it seems like a basic protected Samsung 2600 mAh cell (according to the documentation). Of course, the company way overcharges (no pun intended) for their own replacement batteries.

Just trying to figure out if there's anywhere I can buy 18650s with these same-side terminals, or even just by the terminal connectors and re-wrap some cells myself. I've looked in the usual places (Mouser, battery space, etc.), but it would help if I knew what these are called so I can search for them.

enter image description here enter image description here

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  • \$\begingroup\$ Questions seeking recommendations of products to purchase, and questions on the usage of products are both off topic here. Given your cell shows a clear contact on the negative end its worth wondering if there's actually a path from there you are missing. But again, usage and sourcing questions are off topic; this site is reserved only for questions of original design, supporting theory, and those offering design-equivalent detail, exclusive of sourcing questions. \$\endgroup\$
    – Chris Stratton
    Commented Nov 25, 2020 at 18:42
  • \$\begingroup\$ It looks like a custom-made end by the manufacturer, possibly a custom cell also. Who knows if they have some exotic circuitry in it - perhaps even serializing the battery to the light. Anything is possible these days. You're probably stuck with them. The good news is, there can't be any fakes. \$\endgroup\$
    – rdtsc
    Commented Nov 25, 2020 at 18:47

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The end is a double-sided PCB which contains the protection circuitry on the other side.

Typically this would protect against some combination of over-charge, over-discharge and over-current.

Here is a typical circuit from a Chinese source:

enter image description here

This is in contrast to unprotected 18650 cells as one might 'harvest' from a laptop battery pack, which rely on circuitry outside the cells for protection.

So your PCB is designed with the terminals on one end, which is not that big a deal if you pick the right end, to make the product more convenient (and lock you into one supplier).

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These 'one-sided' concentric-terminal batteries do exist. I have a couple of devices that use them, all by different manufacturers.

Sadly, I don't know how to order these specific 18650 batteries other than by visual inspection. My local electronics place, which has everything else, doesn't carry these. They do know about them, but I guess they decided it wasn't worth stocking them. :(

Sorry I couldn't be more helpful.

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