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Comment by eqvinox | Hacker News Reader

I'm confused that noone is pointing out most protected 18650 cells won't even fit in those holders, since protected cells are generally in the 18690…18700 pseudo size range. That's too long to get into those holders.

Source: the holders are likely Keystone 1042 [https://www.keyelco.com/product.cfm/product_id/918], which I've worked with before. For a protected cell, cf. for example https://imrbatteries.com/products/panasonic-ncr18650b-3350ma... - note 69.41mm length.

[ed.: it's the China equivalent of a Keystone 1042, https://www.lcsc.com/product-detail/C2988620.html - I can't confirm but am 95% confident a protected cell won't fit; if it would, the hold on an unprotected 18650 cell would be quite loose.]

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That is mentioned in the article, although could perhaps be more emphasized since it does mean the "obvious" fix is not possible:

Commonly available protected 18650 cells don't fit in the badge's cell holders because they are slightly longer.

I did indeed totally miss that, thanks for pointing it out!

FWIW, I have battery holders that deathgrip unprotected cells, so even finding a proper holder for those is a crapshoot.

I’ve worked with the Keystone holders and can confirm that those will hold protected cells, at least some I got from nkon.nl

That's a good tip for safety conscious visitors because the webshop is in the same country. Probably a good idea to put it on the event wiki. Is the event still going on?

The last day will be this Tuesday.

Can you please specify the exact type of these cells.

A friend found a 68.8mm cell that fits; the Keystone holder caps out at 68.88mm. Most protected cells are 69.2mm…69.8mm.

The Keystone holders are nice but expensive, but they do not fit most protected 18650 cells, and I don't like the PCB mounting options.

I designed my own 3D printed 18650 holder for my project, including a positive battery tab cut-out to prevent reverse battery insertion. I get to decide how big the battery can be, and protected cells are 100% the way to go.

I've never had a problem with a short with the protected cells, and my circuit also cuts off power to the load using a mosfet, if a short ever occurs. It's been working great for years.

Funny, I'm also going with a 3D printed 18650 battery module... for a lepton (FLIR) project.

Sure, that means the idea of using unprotected cells was already there when the holders were selected :)

Yeah, I'm just saying, you can't even buy regular protected cells and put them in, because they won't fucking fit. I do think "actual" 18650 protected cells exist, but they would be rare and expensive because you can't build them out of mass manufactured bare 18650 cells (for obvious reasons of where do you put the damn protection circuit.)

Ah yea then I misunderstood. That's right you can't easily switch out the cells for protected cells yourself :(

The nomenclature, as commonly used isn't precise enough.

18650 means 18x65mm, but "protected 18650" usually means that cell with electronics stuck on the end, which ends up at 68-70mm long. Nobody calls the result "18680" even though that describes it more precisely.

There isn't a common cell slightly shorter than 18650 to produce protected cells that fit in every holder designed for 18650. The AA-size (but not AA-voltage!) 14500 often does come in protected versions that are exactly 50mm long, based on 14430 cells.

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