The problem with wiring your pump directly to your van battery, as has been mentioned, is that you will be running it flat out all the time, and therefore much more possibility of running the battery down to a point where you cant start!. I have my pump controller wired to my van battery, and have been using it like this for about 4 years now. Had to replace the van battery about a year ago as it was starting to get a bit tired, but other than that, no problems. I have a couple of streets where i am parked up about 3 hours, cleaning windows, but never any problems starting afterwards. My pump controller has not caused any problems either during that time, other than the dial breaking off (I can still use it fine like this though). It was from cleaning spot, i had ordered a digital one, but they were out of stock, so i got the analogue one instead.