So, there are a lot of questions about my battery choice. ZeroPhone is known to work with LiIon batteries that have 3V-4.2V voltage range, so both 18650 cells and pouch cells will work (though some chemistries, such as LiFePO4, are not yet supported). So, why not decrease the thickness of the phone by using some kind of pouch cell by default, as opposed to bulky 18650 cells?

The main problem is - I don't actually have control over which batteries others will use, I can only suggest. Lately, lithium batteries are really hard to ship, so when I send ZeroPhones, best I can do is include a holder of some sorts. So, the kind of holder that I include (and assembly instructions which I include by default) is going to the way I can make I suggestion. Currently, I include a holder for 18650 batteries, and instructions are also tailored to these. It's done for multiple reasons:

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18650 are the easiest to source. Sourcing is an important thing here - even if I send out a fully assembled ZeroPhone, the recipient still has to source batteries (since, again, I can't ship those without getting the shipping cost up). With pouch cells, you'd need to source one that fits into 4x10cm dimension (so that it doesn't stick out the ZeroPhone outline), has enough capacity and the right connector. Do I want to subject somebody to this sourcing process when it's all that stands between a working and a non-working ZeroPhone? No way. 18650 cells are easy to get from vape shops, regular online shops, and even harvest from laptop batteries - the latter is where I got all my 18650 cells from. 18650 standard size and resulting capacity average. With 18650 cells, you know you're getting about 2000mAh of capacity in one in the medium-to-worst case, you know the length is 65-67mm, the diameter is 18mm + 1mm for isolation, and these things won't change significantly, so you don't have to mod a ZeroPhone case for your battery before printing it, you don't have to worry about finding the right one among many because even the worst ones will likely still fit the requirements. Price. 18650 cells are ubiquitous, and they're cheap. Especially compared to pouch cells - I can get 18650 batteries in my hometown for 3.5EUR/one, and pouch cells start from 10EUR/piece (those are not even quite suitable ones). And then, there's harvesting! Safety. It's much harder to pierce a 18650 battery, they have venting mechanisms built-in and they're really unlikely to burst in flames - unlike the pouch cells, which are much easier to pierce inadvertently, and they will react violently, and they don't quite have a venting mechanism - they'll just inflate, until they crack the case they're in, or, worst case, get pierced by something.

Having said that, I know that thickness of ZeroPhone has to be reduced, and there are safety precautions that can be taken. So, I welcome everybody that'd like to mod their ZeroPhone to accept a pouch cell instead of a 18650 bank, and I'll eventually provide both instructions and materials for such a mod (namely, JST pigtails and something that could be inserted between back board and the battery to prevent damage.

[TODO: insert a photo of experimental ZeroPhone with a pouch cell here, just need to take it]