It is such a waste if you cant use a cigarette lighter power source for a computer. Car PC Charger/Adapter changes cigarette lighter power source to a laptop power source, so you can use a laptop without worrying about running out of batteries! Of course this charger will let you charge your laptop battery too. So, if you charge your laptop while you are driving, you dont have to bring an AC adaptor with you at the destination. It is a wonderful adaptor that helps you in a car or at the destination. How to use this adaptor: 1. Please check the voltage of your laptop and the AC adaptor first. 2. Set the voltage switch located on the front of Car PC Charger/Adapter to the desired voltage. 3. Select the same size plug as your laptop AC adaptor plug. 4. Attach the plug that you selected to the end of the Car PC Charger/Adapter cable Connect Car PC Charger/Adapter to a cigarette lighter socket first, and then connect AC connecter to your laptop. You can turn the computer on as usual.