A power generation device is provided. The power generation device can include a magnetic coupler. The magnetic coupler can be associated with a maximum torque output. The maximum torque output of the magnetic coupler can be based on a size of the magnetic coupler. The power generation device can also include an alternator coupled to the magnetic coupling device. The alternator can convert kinetic energy received from the magnetic coupling device into a current. The kinetic energy can be generated by the magnetic coupler using a rotational force transferred across the magnetic coupling device. The power generation device can also include a power converter device coupled to the alternator to shape the current from the alternator such that the maximum torque output is sufficient to cause the power converter to output a threshold current sufficient for operating a well tool powered using the power generation device.