10-12 batteries, if you dont want to charge any while your running (my charger connects to my truck battery). But the actual run time of batteries varies far too much do to all the variables. Battery itself plays a huge part. Then there's the vehicle, driving style, terrain, and so on. How long a battery takes to charge is also just as diverse, some high end chargers have claimed 5 minute charge times, something absurd like 12C. You charging for 12 hours vs me charging a grip of batteries in the same time or less are still pretty close. There are pros and cons no matter how you look at it.