Longish story.

Scenario was son had done deal to trade his car in and coming down through Gloucester warning light about low battery came up on dash. 17:00hrs Lashing rain. Has to get to Bristol that night.

Found a Kwik Fit shop (Thank you Google and iPhone). Kwik Fit very helpful. Diagnosed the problem as stemming from the regulator on the alternator. Too late to repair it and anyway car was sold. Popped in new battery. Got to Bristol that evening. (No air.con. No lights. No heater. etc. etc.)

Next morning auto electric shop in Bristol checked to find that alternator was fluctuating in its charge. Would we last a 250 mile journey ? He didn't like to commit himself but said he himself would risk it.

Got 250 miles under belt no problem and battery was placed on charge. Within matter of hours it was up to scratch so next day we finished the last 100 mile leg of the journey.

I guess the alternator was possibly under charging the battery by a small amount.

Anyway. Assuming the alternator wasn't charging at all how many hours does the team think the engine would have run on a new battery alone ?