solve:

1. Once the voltage is adjusted to a certain value, there is no way to increase it. There are two possibilities: 1) the output voltage limit switch inside the controller is turned on

2. Long press the "knob" for 0.8 seconds to enter the function menu, then turn right to find UL180 (this value may be any value or the highest value we just adjusted the voltage to).

3. Adjust the parameters to UL220. 2. It may be a coding switch fault in the controller. If it is a fault, it needs to be returned to the factory for repair.