Quick Power Supply for a Macbook G4

A macbook that was shredded to pieces was recovered over the summer. 

Before pouring time into it, i made a quick powersupply to see how damaged it was.
This documents making a quick power adapter for a Macbook G4.
(i'm not a mac person, i did this for the sake of bringing hardware back from the dead)

This is also useful if your stuck in the congo, and need to power a macbook g4 off of 2 jeep batteries and hack apart a mini cell phone ear piece for power. Jack Bauer approved.

Build & Test Conclusion Image Directory
Component Purpose Image
Simple 3/32nd in audio jack About the same size as an apple legit power jack internal plug
only moderately over priced at your local radio shack

Probably the most ridiculous use for the 3/32nd size, 2A over a mini headphone size cable, If apple ever goes into power engineering i'm leaving.
Here is another image of the connector, next to a small battery for scale
Multmeters ammeter / voltmeters are very useful, but not necessary
Crufty Power Supply 24v, ~2A power supply. i found this crufting years ago, it was for a childs scooter, probably a charger. After scoping the outputs, i found that with the addition of 100uf of output capacitance it was clean enough for me to try it out on the macbook. As the current output is less than optimal, i let the macbook charge before attempting to boot. if the macbook attempted to charge quickly while booting it would possibly brown out the power supply.
Even if you only  have a 24V 1A supply, use it to charge the laptop batts, (leave it pluged in with the laptop off), you could boot from the internal batts later on
If youve got access to a varable power supply that can do 2 A use it (like this one)

Build &Test:
Action Purpose Image
Solder solder wires as shown. check for high impedance state between wires before applying power (there shouldnt be any resistance at all between the two wires, if there is (and its a low value) youve got a solder bridge. fix it.
Test before booting the machine, have an ammeter in series with the supply, check the amperage consumed. ~1 A (while the mac is off, but charging) is appropriate. if its pulling far more than this, something is wrong. if you dont have an interna battery, but its not pulling crazy amounts of current, attempt a boot.
Here is an image of the adapter plugged into the G4 macbook,

(Black USB drive has Ubuntu Kernel on it, for loading legitimate OS)
Hurray it works!  
Macbook running from 2 lead acid gel cells, thru an ammeter and a fuse.  Macbook Battery also charges!

fuse was necessary to prevent large amounts of damage if incorrectly wired.
macbook consumes 1.2A at 24V (while not charging internal battery) and upwards of 2.2 A while charging internal lithium cell


People who worked on this project:
Dane Kouttron
(EE/ soldering / OS stuff)
Emily Krupczak
Found the mac, helped out alligator-clipping / finding screws / generating ideas

Special Thanks:

Rensselaer Polytechnic Institute 
Electrical & Electrical Power