Ask HN: Can we still run mobile computers off AA batteries? | Hacker News Reader

Ask HN: Can we still run mobile computers off AA batteries?

9 pointsnxobject5 comments

This question came out of a lunchtime conversation with some colleagues, none of us who work in hardware or embedded: there was a period of time, up to the late 90s, where certain mobile computers and PDAs could be run off AAs for a long period of time, with sacrifices of I/O, display fidelity, and storage. Examples at the end.

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

Seems like you can get AA power pack that has a USB output, and use that to power/charge a standard smartphone (maybe one with a removable battery, if you want to be a purist about it)? https://www.coolerguys.com/products/usb-aa-battery-charger-a...

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.

Some thoughts:

- 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.

Yes!

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!).

> Beyond size and aesthetics, is this possible today – or is this no longer possible?

[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…

[1] https://forums.raspberrypi.com/viewtopic.php?t=3261

Yes, mobile computers can still be powered by AA batteries, Like it's less common in modern devices due to rechargeable battery and the long mobile battery life. there are still portable devices, like handheld gaming consoles, portable radios, and other types of computers.

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