Quote: Originally Posted by
Shad0wca7 
Not going to work, transient voltages and other nasties will ruin the laptop. Added to that it probably requires more than the ~12v your car will probably supply. Pick up a cheap adaptor on eBay and hard wire it.
Uh...I think that is what he's saying. If I read the OP correctly, he wants to use an automotive laptop brick and just slice off the cig adapter then hardwire it to pos and neg. Just make sure you are careful with polarity!
ShadOwca7 is correct, e-bay is great for those things.
I have run my system like that since installed, no problems. The brick converts the 12v supply to the 18-19v your laptop wants, and I believe the output is regulated. It is on mine at least. So, even if the car is pumping out 12-14v, the brick handles it and sends out a clean 18v or 19v or wharever.
Good luck!