Autosinger - yes - don't leave the laptop plugged in while the engine is off - you will drain the battery.
I surmise you travel a lot, hence need a way of recharging your laptop between normal visits to a 110 outlet. Otherwise, I wouldn't bother.
My suggestion would be to buy a space battery. All laptops are different, but with some you can remove a peripheral, such as CD-ROM device and put a second battery in its place.
Would need to know more details to be able to advise further.
FWIW, I have several clients would travel overseas, so my area of expertise in mobility and computers is fairly good. I currently dealt with one of my clients who works for the World Bank and was in Bulgaria and in need of the oddest of adapters for a modem connection, but Targus makes anything you can imagine in that area. Anyway, if you need further guidance, let me know more about the laptop and travel habits.