Depends on what your laptop needs. Most laptop bricks supply 15VDC +/- 3V. My Dell's brick outputs 17VDC but looking at the specs, it only needs 14.5V; the extra is for the charging circuitry.

So, it's probably easier/cheaper to find/build a DC controller to step-up your 12V cig. lighter to whatever your laptop needs.

>--------------< --Chemguru 99 CSVT Frost /Mid. Blue 00 Suzuki SV650 Red, Naked