Can the black wire of the rectifier be left unconnected?

[LeLyla]

No, the black wire of a six-wire motorcycle rectifier is generally the voltage sensing wire, which should be connected to the ignition switch line that supplies power to the entire vehicle. This means the black wire should be energized when the key is turned on. The rectifier uses this black wire to detect the battery voltage and then determines the charging output voltage. If this black wire is not connected, the rectifier cannot detect the battery voltage and may assume there is no battery in the circuit. In such cases, it might automatically reduce the output voltage to protect electrical appliances from being damaged by excessive voltage (the battery itself is also an important voltage stabilizer). Therefore, not connecting the black wire could result in insufficient charging, leading to battery depletion.