Hello Brian,
I am not familiar withe the MKIV version, but unless it has changed radiacally from earlier models, I echo Ray(C)'s comments.
I would add though that as the output is designed purely as a charger and not a power supply, the voltage will not be stablised or smoothed enough to run most electronoic items (e.g. televison radio etc)and in fact it may damage some items.
The device requires the load of a battery to smooth its output.
I would have thought the box was rather big and clumsy simply to provide power without the battery.
As a reasonable alternative, check maplin.com or ebay for 13.8 power supplies. These are quite cheaply for running automotive devices on a test bench and available with quite large current capacities, and some are suitable for running the 12V systems in a caravan.