This looks very much like you want to power a note book computer from a car battery.
If so, do a search for DC/DC converters if you *really* want to build your own. It may be cheaper to buy a ready made one, there are a few on the market for just that purpose :wink: .
Another option is to use an inverter and the notebook's power pack.
Good luck
If the learning experience is what you are looking for, then search for boost converter (or dc/dc convert as mentioned). Otherwise, buy it, it is cheaper.