This is a unit of measurement for battery capacity, obtained by multiplying a current flow in amperes by the time in hours of discharge. (Example: A battery which delivers 5 amperes for 20 hours, 5 amperes times 20 hours, or 100 ampere-hours.)

Very simply if you have (2) 500W motors at 24V that is about 42Amps max draw (1000/24) If you have (2) 12V 35Ah SLA batteries in series (24V at 35Ah) then 35Ah/42= .8h or 50min of run time. This is in a perfect world with no losses. As the motors get hot and the batteries get hot there are losses so the actual run time would be less.