Although we all know solar charge controller is important, some people may don't understand how it works.

Now we presume we have 12v DC solar panels and 12v DC device.First let's consider what happened if we do 

not have solar controller.

Solar panels will be effected by the light intensity at different time. In the daytime, the strong light strengthen

the voltage ,so the battery will be heated. When the temperature is too high , the baterry will be damaged. At

night there's nearly no sunshine,the baterry voltage will be high than the panel's.We all know the voltage will f

-low from high to low,so it will reduce the efficiency of devices 

While we have the solar controller,it will control the voltage at the rated level and ensure the flow in certain direction

which will improve the efficiency of devices.