Upgrading The Battery In A Wrist PDA

No, your eyes do not deceive you. That’s a wrist-mounted PDA. Specifically, a Fossil Wrist PDA, also known as an Abacus, that was sold from 2003 to about 2005. Yep, it’s running PalmOS. [mclien] has had this watch/PDA for a while now, and found the original 180mAh battery wasn’t cutting it anymore. He made a little modification to the watch to get a 650mAh battery in this PDA by molding a new back for it.

The original PDA used a round Lithium cell, but being ten years old, the battery technology in this smart watch is showing its years. [mclien] found two batteries (380mAh and 270mAh) that fit almost perfectly inside the battery.

The new batteries were about 3mm too thick for the existing case back, so [mclien] began by taking the old case, adding a few bits of aluminum and resin, and making a positive for a mold. Two or three layers of glass twill cloth were used to form the mold, resined up, and vacuum bagged.

After many, many attempts, [mclien] just about has the case back for this old smartwatch complete. The project build logs are actually a great read, showing exactly what doesn’t work, and are a great example of using hackaday.io as a build log, instead of just project presentation.

22 thoughts on “Upgrading The Battery In A Wrist PDA

  1. I did the same thing with an old Plam TX (with charger) I got for $2 at the Goodwill, replaced the dead battery with a cordless phone battery from the dollar store and it works! Plam OS, Wireless, Bluetooth and as an added bonus is looks like a total piece of s**t!

    1. Need details, my brother just bought a box of T|X palms. 9 of them need new batteries. But if you can say which batteries are $1 as opposed to the $12 ones he found, that would be a great help.

      1. Trust me, you really don’t want to do this, I did it just as a “so could I do this” thing, the battery won’t fit into the case, I cut a hole in the case with an xacto knife and ran the wires through, the battery is stuck on the back with double sided tape for Christ’s sake! Really if your bro wants anything like a workable Palm go with the $12 dollar batteries, seriously.

    1. The screen on that *is* already 160×160, with 4-bit greyscale support. The hardware itself (the LCD controller is integrated with the 68k SoC) won’t support 320×320 color. There are PalmOS handhelds that had 320×320 or even 320×480 screens but they used an external LCD controller for the most part, and the ones that had an integrated color-capable LCD controller were ARM-based PalmOS 5 devices, using an OMAP or PXA2xx-class SoC.

  2. I’m curious why you chose to fabricate a whole new back, rather than just make a 3mm spacer to mount under the original back. Since this would be in compression with no other significant forces, fiber reinforcement shouldn’t be necessary.

    I understand if you were trying to develop skills in creating miniature parts in fiber-reinforced plastic, but otherwise this just seems like it was the hard way.

    1. 2 reasons this won’t work:
      1) the screws are to short (and at least in europe getting the inch sized screws with more length is close to impossible)
      2) the original back is shapes differently (close around the coin battery). but I use the whole foodprint of the back. (Look into the logs of the project, the picture will explain that).

      And yes developing the skills for miniature fiber parts was part of the reason/fun of the project (wan will help out forthe running project)

    1. It helped, that I didn’t know about the amount of fail and retry before I started :-)
      Oh, and I didn#t uploaded the pics of the final parts (have a look on the project logs)
      And in response to some forum questions, I offered a replacement service for those brave enough to send the wristPAD. (I have to count the original back plates at home to estimate the amount of relaced batteries I did..)

  3. I have one of these watches somewhere in a box. I bought one when they had them for about $30 on Amazon and they were getting rid of them. I forget when it was, but it was long after PalmOS was a power house (at least by internet time measurements). Despite that, I looked forward to it because I had a ton of old PalmOS apps from my days with a PalmPilot and later a HandSpring Visor. Many of those apps would still, to this day, be awesome to have in watch form, even if the screen is small. Unfortunately, my unit had a messed up touchscreen/digitizer, and I never got around to getting a replacement before they ran out of stock.

    I’d still love to get it up and running. I’m sure it would need a new battery too (not that they ever held more than a day’s worth of charge), so this is great to see. Even if it’s just to see the old spirit of PalmOS.

  4. OK, time to clear it up a bit, since Brian caught me by surprise.
    This is a rather old project of mine, which is mostly finished, but the documentation isn’t. So I just took the chance to document it, because someone asked me how I plan to make the case for my new project. So just be a bit patient until I finish the docu for this project.
    I will post the log about the final working mold, followed by a detailed instruction how it will work in general to get a working mold. This is manly to prevent someone who has to solve a similar problem making the same/as many problems as I did.
    I used the watch frequently until the screen starts dying. And I like PalmOS for the simplyness and the fact it hasn’t a cell phone connection.

    1. But you are aware that nearly ALL mobile devices use LI based batteries?
      And there are about me and 10 other people using this mod without problems. So what is your point exactly????
      It seams you haven’t understood the LiPoly cells are contained and not worn direcly on your skin (remember: the final version isn’t documented jet!)

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