I have four UniSolar panels on the roof of my RV. Do I need a blocking diode?

I wouldn't think so. The charge controller should have them built in. Besides i have never lost power from my batteries back to my solar panels without them, even without a charge controller.

Thank you for the info. I took out the blocking diode and found no back feed at night. Also, there is a lot less heat in the RV compartment.