Buzzing sound from solar controller??

[JCB80]

My travel trailer has solar panels with a switch energy SWE 12-30 controller connected to 2 x 6V batteries. I disconnected and removed the batteries (stored indoors) for the winter. I just went into the trailer for the 1st time in weeks and noticed a very obvious buzzing sound. As mentioned, it is not connected to any power, the batteries are removed and the cables are not touching each other, not touching any metal, not wet... The buzzing sound is coming from the controller box and the screen is illuminated but nothing displaying on it (the usual numbers).

Any ideas what is causing this? Must mean electricity is coming from somewhere, but where?

The trailer is covered with a Adco cover but obviously the solar panel on the roof can still get some sun. But as I said the wires are not touching anything.

Thanks in advance!

[GaryUT]

You need to disconnect the solar panels or cover them to stop any light from reaching them.


Most solar controllers have a warning in the manual to not connect the panels if the controller is not connected to the batteries. I added a switch between the panels and the controller.


Gary