I have a few problems and one of which is getting parts the other is shipping. So I have to design things that I can use much of the local supplies. The part I am lacking is only the motor this way and those little DC motors are the easiest and cheapest to ship.
Well you need a 48v motor (running a 24v at 48v will kill the motor quick)
How fast and far do you want to go?
48v will get you 22mph and 12ah will give you 20miles
No I would just get a 48v motor and run 48 volts to it with smaller 12v batteries Same amp hrs around 100. The limiting factor is going to be weight and room I have about 18" x 18" to work with but I only made that so as to handle two 12v deep cycle batteries. anything over 100# or so is not going to be as good also.
The other reason for going with the sprocket type motor is I can gear it for the speed I want with the sprockets I use. If I run a 24v motor geared to only go 10 mph I will not be drawing that much amps.