I got curious after @licryco commented. If the whole thickness is supposed to be 15mm, we have to reduce from that the back plate and screen, which would take about 3-5mm. (edit: not Circumference) Diameter of an AA is 14.5mm while AAA is only 10.5mm - so I accidentally got that right the first time. I think you can get that size in lithium also. A 18650 [which btw. is in the dev board, so @licryco wasn’t that far off] is whopping 18mm and would require a Nokia Pureview level hump on the back (not necessarily a dealbraker - some of us are planing to add a protective case on top of it). CR123a is 16mm. And an 3LR12 is 22x62x67mm. There also unfortunately isn’t space for this power source:
Maybe a hand crank for emergencies? And while we’re hoping for stuff, I wish it’d have 3 usb-ports, so for convenience I could use one of them for a QI adapter (which also would add to thickness), one for display/hub(keyboard+mouse) and one for other peripherals. Maybe I need to glue a hub on the end of the phone… Btw. wouldn’t Qi be an added security feature, as no possible data connection via malicious cable or powersource/comp?