what do I need to do to disconnect a solar panel from a battery to protect the panel?
Know that solar panels almost always incorporate a blocking diode to prevent a battery from back-feeding through an un-illuminated panel. Know that solar panels are usually connected to a battery via an electronic switching charge controller, not directly connected. Know that when a solar panel is open-circuited (disconnected from everything) it's terminal voltage will rise to almost twice it's nominal voltage. (22V is common for a 2V panel), unless it is stored in total darkness.
