Forgot something important in my last post. Powering the CD32 with the laptop-battery should be no problem.
Stedy said this about his expanded CD32-system: "My SX32 Pro, 030/50 MHz + FPU + HDD uses 2.19 Amperes @ 5V and 0.077Amperes @ 12V".
This leads to that the power-requirements of Stedy's CD32-system is: 5 * 2.19 + 12 * 0.077 = 11.9W
To compare these power-requirements with how much juice the battery from a laptop can deliver I asked a friend of mine about the ratings of the battery used in his old P120-laptop (a Digital HiNote Ultra II). The battery was rated at 3.3Ah @ 7.2V and that gives the capacity: 7.2 * 3.3 = 23.8Wh.
If I use the power-requirement calculation I made on Stedy's CD32-system it would be able to last: 23.8 / 11.9 = 2h
These calculations are a bit rounded, but even if your CD32-system would use the double amount of power you would still be able to run it 30min on a similar battery. Worth mentioning are the fact that the this battery was from a very old laptop and a never battery will have much more capacity.