Step-up volt convertor - Laptop charger

I ordered this step up convertor from china to charge my laptop from my camper battery
http://www.banggood.com/DCDC-Adjustable-Digital-Converter-Step-Up-Boost-Module-USB-335V-p-931237.html

and added a case with place for a standard 10A switch as well.
I use it for charging my latop from my camper battey, and it seems like the cheapest solution and most energy efficient, with a switch for the display that switches between current, volt input and output.

The case is made of two attached