Beyond size and aesthetics, is this possible today – or is this no longer possible?
(For example, do modern displays hoover up too much energy? Do 5G, Bluetooh and WiFi radios constantly suck power?)
Here were some examples of late-era portables that ran off AAs that we came up with:
- the Psion palmtop series used a couple of AAs, plus a coin cell battery for memory; and ran for a week [1]
– the Apple eMate, a Newton (ARM) in clamshell laptop form, which ran off 6 AA rechargable cells that could be swapped for off-the-shelf AAs, and ran for a week as well;
– similarly, the AlphaSmart Dana (Palm platform on 68k/ColdFire) and HP 200LX palmtops (PC-compatible) could be run off two AA batteries for around 30-50ish hours.
[1] https://news.ycombinator.com/item?id=40438434
You can do some rough back-of-the-envelope math for this. A typical smartphone might last about a day with a battery about 4500 mAh @ 3.7V nominal = about 16 Wh. That battery pack of 4 AAs is about 48 Wh, so it should run the phone for 3 days or so (with some losses). But depending on the phone, it may or may not be able to run off a standard USB outlet anymore (USB-A is usually limited to around 10W, some newer phones need ~18W to properly charge while on). But anyway that should give you an idea. With batteries and some electronics, you should be able to make a modern smartphone run off AAs. Here's a youtuber showing something like that: https://www.youtube.com/watch?v=-qObYrj1Foc&t=633s (or a DIY version: https://www.youtube.com/watch?v=TaoCPv0GTSg)
The question then is if you consider a "phone" a "computer". If not, probably you can find some Raspberry Pis, Beaglebones, etc. with a similarly low power draw. Or an Apple Watch, for that matter. From there it's just an issue of having enough AA batteries in series and some voltage converting electronics/USB ports to connect them to the smartphone.
There is nothing inherently impossible about this. Low-power electronics exist (in everything) these days. We just don't use AA batteries because li-ion is more energy dense (capacity per volume) than most AA chemistries, and if you're going to use li-ion anyway, a flat form factor is typically easier to carry around in a pocket than cylindrical cells.
- The banal answer is yes we can use the same components and build the same style of machines.
- A slightly more nuanced answer is that we have much more efficient components these days, from CPUs to displays. So we could do better now for the same functionality.
- Adding a nice display, wifi, bluetooth, etc should be possible for a small display. For reference, the apple watch has a battery capacity between 250mAh and 550mAh. A single alkaline AA battery has over 3000mAh.
- Eink displays have some tradeoffs but are very low power and are getting better at display update times.
- OLED displays can be quite power efficient. Especially the monochrome ones.
But of course there isn't really a market for this style of device anymore with smartphones dominating.
Take a Raspberry Pi Zero and connect it to these:
https://www.amazon.co.uk/Battery-Holder-150mm-Wires-Leads/dp...
https://www.amazon.co.uk/voltage-converter-Raspberry-batteri...
Allows you to run a Raspberry Pi Zero from 8 AA batteries!
I can't remember where I'm getting this figure from, but I think it accommodates for about 3 days of runtime (obviously dependant on what you're doing with your Pi!).
[Non-serious answer] yes, you just need a lot of AA batteries!
[serious answer] yes. For example the raspberry pi uses a “fully featured” Linux OS and it looks like it could run for a few hours according to this [1] forum discussion.
But probably would need specific hardware to run for a long time, and sacrifices in OS features…