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Duty Cycle

Duty Cycle is the ratio between the effective motor voltage and the battery voltage, expressed as a percentage.

A duty cycle of:

  • 0% means no voltage is applied to the motor
  • 50% means the motor receives approximately half of the available battery voltage
  • 100% means the motor receives nearly the full battery voltage

Duty cycle is one of the most important parameters affecting motor speed. As the motor accelerates, the duty cycle generally increases. Once the controller reaches 100% duty cycle, it can no longer increase the motor voltage. Further increases in motor speed typically require field weakening, a battery with a higher voltage, or a motor with a higher KV.

⚠️ Duty Cycle is not the same as throttle position. A throttle may be at 100%, but the duty cycle can be significantly lower if the motor is operating under load, accelerating, or limited by current settings.

⚠️ Duty Cycle is not the same as power. A motor operating at a high duty cycle is not necessarily producing high power. Power depends on both voltage and current.

Duty cycle is commonly used on VESC controllers for features such as:

  • Duty Cycle control mode
  • Duty Cycle current limits
  • Field weakening
  • Maximum ERPM protection
  • Telemetry and data logging

Example

A motor controller connected to a 50V battery and operating at a 50% duty cycle is applying approximately 25V to the motor.

As the motor accelerates, the duty cycle may increase from 20% to 95% as the controller increases the voltage supplied to the motor.

In simple terms: duty cycle represents how much of the available battery voltage is being applied to the motor.