🔋 Kv
A brushless motor's RPM per volt with no load.
A 3500Kv motor on a 2S (7.4V) pack spins ~25,900 rpm unloaded. Higher Kv = more top-end but more heat; lower Kv = more torque and cooler running.
What it actually does
Kv is the motor's RPM per volt with no load on it. A 3300Kv motor on a fully charged 2S pack spins far faster than a 2000Kv motor on the same pack. It is the single number people reach for when comparing motors, and the single number most often misread.
In practice
Kv describes speed, not power. A low-Kv motor is not a weak motor — it typically has more torque and is what you want for a heavy truck or a crawler, while high Kv suits light, fast, on-road cars. Kv only tells you the whole story once you also know cell count, gearing and vehicle weight.
Worth knowing
Raising Kv and keeping the same gearing is how motors and ESCs get cooked. If you go up in Kv or cell count, gear down to compensate and check temperatures after a short run.
Related terms
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