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PowerBook 500 series Battery Rebuild


Well-known member
...Any chance those of you with refilled batteries would want to crack them open and see what batteries they used? Also (if they did use different batteries than the original ones), dump the battery settings to see if they changed anything?
Only do this to a rebuilt one that is dead (again).  Getting into these things is a bit of a pain.  My post of cracking open the bad one to follow in a bit.



Well-known member
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:

01 battery front.jpeg

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:

02 intellect board 2.jpeg

03 intellect board 4.jpeg

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:

04 dremmel front.jpeg

06 dremmel rear.jpeg

05 dremmel side.jpeg

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:

07 liftoff 3.jpeg

08 liftoff 5.jpeg

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.

12 liftoff 6.jpeg

Finally, we have have the actual battery cells exposed:

09 battery layout 1.jpeg

10 battery layout 4.jpeg

11 battery layout 5.jpeg

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.

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Well-known member
I've been following along as you do this-- using one of my 540C batteries. I used an X-Acto knife and slowly / carefully cut it along the seams and inside the compartment for the circuit board until it popped open. The plastic is pretty soft and I was able to work my way through.  It took about an hour to open it up.

I'll be placing an order for some of the cells on Amazon.



Well-known member
Oh cool :) I'm a bit behind because work has been insane busy the past month.

That battery I opened in the first part of this series is absolutely done. The corrosion was extensive, as I expected.

On the next battery I open I will give your method of using an exacto knife a try. The cleaner the cut the nicer it will seal back up, and I imagine that will result in a cleaner cut than the Dremel.

If I don't get dragged into work Saturday I should be able to do part two then.



Well-known member
Work has been absolutely insane busy lately.  This project is not forgotten, just on hold for an extra week or two until I have enough time to tackle it in one sitting.



Well-known member
I successfully rebuilt my PB500 battery.  I glued it back together with Epoxy. Once I got it back together, I used the Intelligent Battery Recondition and another utility from Lund and reset the battery.  Once charged, I get a little more than two hours life from it.

I opened up my second battery with an XActo knife and have new cells on order.



Well-known member
I used battery recondition and one came back to life without recelling! 1-1:15 hrs of battery life.

Also, both my batteries only showed around 100mv.

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New member
Hello, new to the forum tonight. Was trying to figure out how to open this battery. Have changed my mind. So.... I have one battery and several very good parts of a 520c. If you are interested. Please drop me a line. 



Hello just started trying to rework the two dead battery packs I got with my shiny new to me 540c.  In reading a bit and looking at the battery pack recommendation I am curious if anyone tried a hobby/RC battery pack like https://www.amazon.com/Tenergy-Capacity-Rechargeable-Standard-Connector/dp/B001BA292A ?  It sure looks like it would be the same Tenergy tabbed cells I was planning to buy but these are already pre-assembled.  This pack is 2000mAh and I think the original was 2200mAh so this would look more like a slightly worn battery pack?  Well wish me luck - hoping to keep this 540c running a while longer.



Was able to separate the plastic side top and bottom using this thread instructions and some of the links (thanks everybody).  The battery does fit in the shell pretty nicely.  Cleaned up the board and adapter side.  I could solder it up but am cautious and wanted to poll the group.  If I do this I won't have the thermistor or the fuse that were in the original battery pack.  But the pack is built for RC and capable for fast charge, etc and was built by a battery company rather than yours truly.

Any thoughts about the circuit and whether it will work before I solder it up and give it a shot ?

Anybody know what the function of the blue capacitor looking components do ? 

540 Battery Rebuild.jpg