there can be
it can damage the controller, depending on the controller
you are not supposed to disconnect the batteries from the controller and leave the solar connected feeding the controller
there is NO reason to disconnect the batteries from solar, except to change/service the batteries or cables
no reason or need to disconnect in storage
IF you live in SNOW country and think your panels will covered to the point of NO output and want to disconnect the batteries and bring them inside for storage
then you should cover the panels, disconnect panels from controller, then disconnect batteries
most people don't go thru all that trouble, they just leave everything connected so the solar can maintain the batteries
