Whats the deal with thrunite's (protected?) 26650?

New to 26650s. Never seen a cell like this. So it’s some kind of special CID built inside the battery? Is that the extent of the added protection? What’s the deal with “thrunite stamped onto the negative end? Is that right on the battery casing? Why would they do that.

Can you charge this normally outside the flashlight in a charger big enough for protected 26650s or is it gonna do something weird?

I’d probably recommend a 26650 from Vapcell or Keeppower instead…Thrunite seems to spec ok cells but hard to say what this one is. Protection circuits are just tacked on to the base cell. Looks like this one is all on the top but many are on the bottom only, or on both ends. Little circuit board that cuts current in various scenarios - most do overcharge, over-discharge (heat), and low voltage. That logo may be the bottom of the protection circuit if there are two on this light, or it may just be laser etched onto the can itself…marketing. That’s a pretty long cell, so unless a light was designed for it specifically it’d be wise to put it only in lights that use two springs (rather than a spring and post/contact)…otherwise the positive end may crush inward a little or it could crack the driver board or solder points.

I have doubts that their cell can really do 25A continuous, but if the cell can…will the protection circuit allow it? Last I heard protection circuits had bumped up from 6-8 amps to about 10 amps max…not sure if there’s anything higher available now but maybe so. Not many lights will eat up that much anyway.

Have you seen teardown photos of protection circuits? HKJ did one years ago…different designs through the years but same gist.

He’s got several “general articles” that are great.

Anatomy of a protected cell

General protection info

Added USB charging

I bought a few lights from a member with a few thrunite 26650’s that stopped working within a few charges. I checked the batteries by skirting around the protection circuit and they were good. I removed the protection circuit, rewrapped them and they’re still going strong, though he’ll never buy thrunite again. I understand their circuits weren’t the best on those batteries

Ya I’ve done a few literal protected circuit tear downs myself hah. This looked different. But I think you’re right. It’s just up top. Threw me at first. Still kinda does.

Theres no board at the bottom I don’t think, but its clearly got something underneath the slightly raised flat top. Some kind of black plastic mesh? Really thin. Not like an obvious round board tacked on the end. Idk where they put everything. I think you’re right about the negative plate being tacked on too. It’s just very well fitted. I was expecting a board to be down there. And I think I see where the nickel strip might be. Maybe. It’s subtle. Really blended in. Or maybe its just easier to hide on a bigger cell, or it’s a thicker wrap. Idk. Measures 67-68mm long. It’s definitely not high drain. Or it’s just really overstating it’s capacity. Doesn’t last very long at all at the couple amps I use the light at. It’s like it’s an 18650. It does charge in my vapcell but barely. Not a great fit. Contacts barelyyy reach over the wrap.

I would just unwrap it but I’m probably going to return it and the light it came with. Not a bad light. Not worth the money though.