Definition
The Kv number’s useful because it let’s you figure out how many volts you need to achieve a certain RPM, or vice versa. For an example, a 980 Kv motor powered by an 11.1 volt battery would spin at 980 x 11.1 = 10878 RPM with no load. The Kv rating always assumes no load on the motor, so the actual RPM that your achieve will be less than the one you calculate.