Reviving an old Windows CE palmtop with AA batteries

A Windows CE Palmtop

I have an old NEC MobilePro 780. I got it to install Linux or a *BSD on, and achieved some success with that project (about 18 years ago?!), but the machine really didn’t have the horsepower to be a good UNIX portable (168 MHz NEC VR4121 processor, 32MB RAM, whatever storage you had in the CompactFlash spot), nor was/is the Linux desktop experience really optimized for the screen geometry (it has an 8.1" 640x240 DSTN display). But I hung on to it, because it’s got a great keyboard and it’s perfectly usable as a Windows CE machine, and why not? But over time I’ve misplaced the AC adapter, the battery is toast, and, well, yeah. I didn’t see the point in spending $50+ for a dubious quality replacement battery, so it sat.

NEC MobilePro

 

But at  9.6" x 5.2" x 1.1" and 1.7 lbs., it will totally fit in even a LoungeFly, and a moment of distracted Googling led me to learning about the MC-BA10 adapter, which lets the MobilePro run off of (4) AA batteries. Now I don’t have to worry about crappy Chinese cells in a proprietary battery pack, I can worry about crappy Chinese LiIon AAs in a pack designed to be easy to swap in other “cells” (AAs) if one or more go bad... I can work with this!

So this pack puts out 6V and 3.6W (0.6A). EBL rechargeable LiIon AAs claim 900 mWh capacity each. The OEM battery pack is 7.2V 1500 mAh. The AA pack must be running the batteries in series to get 6V out of 1.5V/ea AAs, so we have 900 mWh at 6V so probably just 600 mAh equivalent to play with, so, like, 40% of the battery life (and probably no low battery warning with the LiIons; save early, save often!).  When everything was shiny and new, the stock battery was purportedly good for “over 8 hours of operation,” so realistically I should be able to get at least 3 hours out of a set of AAs with this thing. 

 

Edit: Thinking about it a bit more ... The EBLs are a bit capacity compromised due to including a USB micro B port and charging circuitry in the AA battery itself, which is convenient but maybe not in this instance. The Tenavolts I’ve used elsewhere are 2775 mWh (1850 mAh) at the expense of requiring a (small, USB-fed) external charger. The trade-offs might favor the Tenavolt batteries for this use case. (Doing the math, the OEM battery pack is 10,800 mWh, if I’m mathing right, the 6V 1850 mAh battery pack is good for 11,100 mWh? So should be pretty close to OEM capacity.)

 

Meanwhile, I can probably find a USB C to DC adapter that could power it off of a battery pack with a suitable voltage ... Pondering. Would make a good distraction-free ultra-portable writing tool, especially since the BYOK project is still not shipping to backers. CompactFlash and Pocket Windows should give me something usable in terms of interoperable data formats and ability to get files off of the thing. (And if worse came to absolute worse, it has a modem, I still have some modems and USB to RS232 serial port adapters, and I’ve always wanted to try building one of these circuits ... The adapter is $21.99 on eBay ...

 

Update: The MC-BA10 AA Battery Adapter arrived today, looks like it’s new old stock. I tried it out with (4) Energizer Max AA batteries I had handy. It works! The handheld initially complains it’s running in a low power mode and you probably wouldn’t want to try to run a WiFi PCMCIA card in that configuration, but it works. I was able to get just shy of 2 hours continuous use out of it before the “your main battery is very low” modal dialogs got to be too interfering. Take-away: You could use it as a palmtop for a bit here and there on the AAs, but for an all day writing session, a different solution is necessary. So that’s either spend $35 or so on an unknown quantity LiIon battery pack (example), or go with my usual solution these days: A USB C to DC5521 adapter. Per the MobilePro 780 manual, the AC adapter supplies 9V at 1000 mA (so, 9W). Almost any USB battery pack can deliver that. I’m going to proof of concept it with the Anker Zolo I already have which, according to the manual, will output at least 9V ⎓ 2A, more than enough. (I kinda want to use this as an excuse to pick up a Nano 3-in-1, but I can’t really justify it when I have probably a half-dozen existing battery packs.)

 

I’ve scanned and posted here the “manual” that came with the adapter, as I couldn’t find it online anywhere. The MC-BA10 is marked 6V / 3.6W, which suggests it’s pulling 600 mA.