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I have a PowerBook 140 that — apart from a dead screen requiring the inevitable capacitor replacement — seems to work well. It has no battery, though, and any available battery will likely have 25+ year old NiCd cells.

What I'd like to do is build a replacement battery pack with modern cells in a 3D printed case. I'm aware that the Apple originals had some kind of sensors in them, but they look fairly simple. What I can't find, though, are dimensions so that a replacement pack will fit snugly into the battery bay. I guess I could spend some hours with digital calipers, a notepad and much swearing, but drawings and schematics would be ideal. Where might such documents be?

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You might be able to find the precise dimensions in the Developer Note that came out around the time of the release; this is what would also have pinouts and specs for RAM expansion and so on.

You'll need to do a little more than just repackage some modern cells and get the right voltage and wattage, however: The PowerBook will try to charge the battery when plugged in, so you'll need to make sure the PowerBook's charging circuit doesn't actually harm the modern cells, which may have very different expectations with respect to charging especially if they're implemented with a different technology.

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  • Hint: While NiCD cells are being phased out in many places, they are not too uncommon in power tool battery packs...
    – rackandboneman
    Nov 2, 2017 at 12:28

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