but surely even the most basic van mount will have a split relay so your battery is getting charged all the time!
perfect example today - myself and big g working today - same run as last month, work finished by 3.20pm as opposed to 4.10 last month (when we were using Varistreams) and although we used approx 50ltrs more, we got the same work done so therefore the same money plus home almost an hour earlier than expected.
added bonus is its just nicer to work with a high flow, brush floats better too.
would you use a manual screwdriver or a cordless to screw in, err, umm, lots of screws.