Keeping retrocomputers going can be tricky enough, but when you’re talking retro laptops, the battery packs add an extra challenge. While one could simply live without the battery, that’s not going to give you the full retro experience. Replacement batteries are long out of stock, so what can one do? Well, one can check out this excellent tutorial by [lazd] on rebuilding an iBook G3 Clamshell battery.
Even if you don’t have this particular laptop, the general process is likely to be similar for PC laptops of similar vintage. (Which we still can’t believe is a whole quarter-century ago.) Luckily for retrocomputer enthusiasts, even Apple used standard 18650 cells in those bygone, halcyon days when computers were allowed to be more than a few atoms thick. They do need to be unprotected, flat-top cells, but that’s easy enough to source.
So it’s really a matter of carefully prying apart the casing (apparently it needs to be Apple-branded; aftermarket cases can’t survive being opened), removing the old batteries, and welding nickel tabs onto the new cells in the proper configuration. One thing that surprised us is that, apparently, Apple did not go in for balancing in those days — so make sure your cells are all in perfect condition and all equally charged before you start, or things won’t end nicely.
Assuming you can pull it off (and your battery pack’s control chip has lasted the 300 moons since its manufacture), you’ll get a not-insignificant 5-hour battery run out of what’s sure to be the cutest clamshell computer at the cafe.
If you are repairing an iBook, while you’re at it, why not upgrade the RAM? You might even be able to fix the screen if it’s succumbing to the sadly-too-common vinegar syndrome.
Probably wise to hack a balance connection into the battery, even in the form of probe holes in the shell.
Or fit a small active balancing board inside?
Christ, unbalanced? That’s horrifying.
Luckily it will be used a grand total of less than an hour anyway, so the risk is minimal
If that board doesn’t do balancing, why are all the cells connected to it?
There’s a datasheet for the “gas gauge” IC on the board at the end of the article. Looks like it keeps track of the charge level, battery age, and things like that. The lack of balancing seemed really weird to me, too.
And that BQ2040 doesn’y monitor individual cell voltages: only the total battery voltage.
So the question remains: why are the intermediate cell voltages connected to that PCB, if not for balancing?
In the forum link on the bottom of the article there seems to be mention of a Mitsumi MM1414 battery protection IC, it can monitor multiple cell voltages in a 3S/4S pack for over/under voltage.
Tried to search for a schematic to see if any balancing is present but can’t seem to find anything.
I’m in the middle of a G3 iBook conversion and one of the hardest parts so far has been sourcing a battery. These are insanely expensive, and I don’t even want to use the onboard battery management.
If you aren’t using the onboard battery management, why not just put your own batteries where the original went? The Clamshell should have a lid on the battery bay, so no one would ever know what you were doing in there. (Not that I’d advise just stuffing it with pouch cells, but… you could.)
Also, once you’re far enough along with that project to want to show it off, please let us know! It sounds like something we’d write about.