All electric motors have a constant called kV. It's a direct relationship between volts and rpm. When you change from 36v (10S) to 48v (13S), the motor will spin 30% faster. How fast it goes depends on the kV. A 36v that spins to 250 rpm has a kV of 250/36, so at 48v, it'll spin to 48x250/36 =...