That's how I have it set up- the run power is coming directly off of the battery and into a relay. I still see the ammeter quite a bit higher when it's on than when it's off. I would say it runs 3/4 of the gauge on the 'charging' side when the fan is on, just a bit to the 'charging' side when off....I just don't know what current this wiring is made to carry for extended periods.