Whats the drain on the battery?
The Dirtworker runs at between 4 and 5 amps. Typical car batteries are 30 or 40 amp hours. This means you could run a Dirtworker for between 7 and 8 hours on a fully charged battery without having to switch on your engine. However, as it takes just 7 minutes to empty a tank, you would need to refill it 60 times to run it for so long.