I thought I'd post this in case anyone was interested in a generic solution for powering their Apple laptops off 12V deep cycle batteries.
MacBooks, and any other laptops that support being run off airline power ports (EmPower)
just need a 15V DC input that is capable of supplying up to 75W.
Here's what I did to hook up my MacBook:
* Bought a 12-22V Laptop Power Supply
adapter from Jaycar - $70
* Set the voltage output switch to 15V.
* Wired a connector from the power supply to a female cigarette lighter receptacle.
* Bought an Apple MagSafe Airline Adapter
with the necessary MagSafe connector (includes an EmPower -> cigarette lighter adapter) - $55.
* Hooked up the lot and checked the polarity at the MagSafe connector
- very important!
* Plugged the new connector into my MacBook - voila.
This simply runs the laptop off the power supply without consuming internal laptop battery power - but it won't charge the MacBook battery (I don't want it to). There are people online who have managed to figure out the correct voltages for it to charge the battery - have a look at your own risk
I'm a bit wary of having a 15V cigarette lighter adapter floating about in the dark, so I've securely gaffer-taped all the bits together for now. Ideally, I'd like to solder/heatshrink a proper EmPower ARINC 628 plug
to the power supply, and superglue the voltage selector to 15V.
Any other laptop that supports running off airline power would work with this (you'd just need a female airline power plug).