Making the voltage higher or lower may change the brightness of the headlight, depending on the headlight circuit design. Generally speaking, headlights have a working voltage range, and the power of headlights will not vary greatly with the voltage, and there may be small changes. Beyond the working range of the headlights, the headlights may not work. Of course, if the circuit is poorly designed, it may happen that the voltage changes, the power changes, and the lumens of the headlights also change accordingly.
