Finally had some time to play around with these batteries. This will be a three part post.
1)How to tear down an old battery
2)Recell a battery
3)How to reset the eeprom, if necessary.
Part 1 is tonight. I somehow went from having 1 PowerBook 520c and no batteries for it to 2 PowerBook 520c units, a PowerBook 540c, and lastly a PowerBook 540 as well as EIGHT batteries for these things all in the span of a few months after having owned the first 520c for over a decade.
The eight batteries vary in condition. The absolute best one actually shows up when in the computer, shows a full charge, fails communications, and the charge dies the moment you unplug the cable. Not even 1 full second of power. It will however sustain sleep mode for ~30 minutes. The next best battery doesn't show up, but does have a measurable charge of around 3 volts. The other six batteries are all flat 0 when tested.
One of those 0volt batteries shows substantial signs of corrosion, and actually pulled a few of the battery pins out from the second 520c when I went to remove it (aside from the few missing pins, the second PowerBook 520c seems to operate how a PowerBook with no battery installed would operate, amazingly enough).
So we have our Guinea Pig for the battery rebuild series:
Start by removing the contact cover and the part that holds the battery in the computer. The contact cover will slide off easily. The large part that holds the battery in will have to be rocked a few times and will naturally want to pop off one direction more so than the other.
Remove the Intelligence circuitry cover:
There's no other way of saying this. This part sucks and will be a bit on the difficult side. You really have to muscle the plastic around while at the same time being careful not to let your tool (in my case, a small flat-head screw driver) slip too far in, striking the circuit board. Mine had 8 clips for sure as you can see in the above photos. Surprisingly, the plastic (at least on this one) was not brittle at all. It put up quite the fight. A LOT of patience is needed here. Just try to pop off one section and leave the first tool there, and then get a second tool (another small flat head screw driver) and work the rest of that side off. Eventually it will pop right off when you are down to just a clip or two.
Dremmel the remaining three sides:
The key hear is to run the Dremmel at a slow speed, and just work slowly. You can always go back and make another pass if the cut didn't quite go deep enough through the plastic to see the batteries. Use caution when you are doing the plastic in front of the connection pins. You don't want to cut through the metal.
Don't worry about the built up excess plastic from the Dremmel. In my case, it brushed off easily enough by running my finder over it a few times.
Once you have all three sides cut, using a wide flat head screwdriver, insert into the space of the cut, and turn left and right a few times to finish popping the seal. Move around all three sides you just cut until the casing is nice and loose.
Time to open it:
Facing the battery with the Apple logo downwards and the serial number and/or barcode facing up, very gently open it, treating the circuit board area like a loose hinge. While doing so you may hear a piece of plastic from the "hinge" area breaking. From what I can tell, there is no getting around that. Just take care to not put pressure on the circuit board and be gentle with the area near the connecting pins as the plastic there is thin.
Finally, we have have the actual battery cells exposed:
From here, the battery was an absolute mess. In fact, there was literally battery fluids still in there. I had to wash my hands off after handling it just for peace of mind.
I'm 99% sure that the polarity for the individual cells is going to be positive at the end with the indent wrapped along the side about 1 or 2 mm back, and negative at the smooth end. However, to appease that 1% of me that isn't sure, we will be using the battery that still retains ~3volts for part 2 and 3 of this guide since I can use my voltmeter to verify at the cell which pole is which.