Portable Macintosh 5120 and 5126

Lead Battery Replacement

So, let's make this quick: you finally got your hands on one of these ultra-cool portable Macintosh laptops (model 5120 or 5126), plug it in, try to boot it up and... nothing! You may see the screen go on for a second or so, you'll see some signs of life but the darn thing just won't boot up. In most cases (personally: 5 out of 6 so far) this is caused by the internal lead battery being dead.

There are various options:

Replacing the dead battery is easy! All you need is some duct tape, two wires with connectors (see below) a screw driver, a soldering iron, some solder and flux, the replacement battery and less than 1h of time!

A perfect replacement battery can be ordered from Allied Electronics Inc., the battery is the "Power Sonic Corp. PSG-650". Go to http://www.alliedelec.com/ and look up Allied stock# "621-5015" in their search. The price of the battery is around $17, keep in mind that Allied Electronics charges you a handling fee for orders totaling less than $25 - you may want to order two of these puppies or other stuff (solder etc.). They typically have this battery in stock and I've always had good experiences with them.

Disclaimer: I take no responsibility for anything here! I've replaced the battery on 5 Macs so far and it's easy. However if you are mechanically inept or like to break things than don't proceed any further! :) In any case: do this at your own risk, I'll take no responsibility, liability, bla bla bla...
Make sure you wear some sort of static grounding device, if you don't have one, perform this operation near a grounded electric device (metal case) etc. water faucet, if you don't know what I'm talking about here then don't proceed :)

When you're ready grab your Mac and turn it so the rear end faces you. Open the Mac by pressing the two rear flaps in and lifting the top half of the case

Once the Mac is open, take a look inside: to the left is the hard-drive, in the middle are some expansion slots and to the right is the battery compartment:

Open the battery compartment by pressing down on the two flaps, take off the lid and take out the battery. Take a look at the dead battery and notice the two golden-colored contacts! I like to re-use these strips since they are totally corrosion resistant! You'll have to convert your new battery to connect to the two tongues inside the battery compartment:

  

I like to take two little wires with female connectors (buy them at an electronic surplus store or make them yourself) that fit the terminals on your new battery:

Carefully break open the old battery without damaging the cells inside! Lift of the lid, take out the golden contact strips and put them aside! Take out the cells and remove the foamy cushion strip and put it aside! Now take one of the wires, it should have the battery connector on one end and just some blank wire on the other. Take the blank wire end and using some flux (if needed) solder it to one end of one of the golden contact strips. Take your new battery, check polarity and line up the strip on the correct side, experiment with the placement and bend it around the top edge of the battery once you've found the right placement. The placement should be right on top of the contact and partially overlapping with the raised middle of the battery. Repeat with the other wire/strip and connect the wires to the battery terminals. If you're not sure than compare the placement of the contact strips on the new battery versus the case of the old battery, they need to be very close! Take the foam pad and put it with the sticky side onto the bottom of the battery, secure the contacts and the pad with duct tape, I typically use two to three layers. The pad will add a bit of size to the new battery to make it a tighter fit in the compartment.

I typically let a little bit of wire stick out from under the duct tape, it makes it easier to remove the battery from the compartment, also notice the foamy cushion:

Final test: make sure the battery contacts line up with the tongues in the compartment:

Insert the battery and do a test run! Everything OK? Great! Close the battery compartment lid, if you feel that the battery has too much play add a little foam strip or something to keep it in place but normally that shouldn't be required.

 

Close the case and you are done!

As an alternative you can also try to fit the new battery into the old shell, however the PSG-650 that I had was too big for that.

Another option is described at http://www.lowendmac.com/pb/portabattery.shtml but that's permanent :(

 

Thanks to http://www.jagshouse.com/batteries.html where I first saw the PSG-650 mentioned!