This is a multifunctional controller that charges the battery more efficiently than the cheaper PWM controller. For my AGM 35 Ah battery it worked straight away without any changes. The display is very nice, it has icons that show what's going on. I connected my 12 to 110 volt inverter load directly to the battery and didn't use the two panel load connections because the controller can sometimes turn off the load, which I never wanted. The instructions are written in Chinese-English and it was confusing when I had to remove two screws to install. This meant loosening the screws for the wires rather than removing the cover from the panel.