How long would you get on your car battery before it went flat ?
Hi Mike, the simple answer is "How long is a piece of string?"! It depends on the car - small petrol or big diesel, and condition of battery - if 5 yrs old and knackered - not long, if like my 405TD, an almost new, very HD 096 battery, probably 12 hours before needing to start and give the battery a boost. I would suggest, give it 2-3 hours, start up and run for 10 mins, if sluggish to start cut time back - if it spins up well, try extending time by an hour at a time.