Here is the rule, that keeps everything working without damage
Connect controller to batteries first
Then connect solar panels to controller
Never disconnect controller from batteries, until you have disconnected the solar panels First
Anytime there is work to be done, batteries changed, cables cleaned etc...
Always disconnect solar panels First
Remember the solar controller is a one way device, power from panels to batteries
It does not work the other way
Connected panels without batteries can and will damage most controllers
You do not need a disconnect on the output side between controller batteries
You do want one on the input side between panels and controller
It's just another battery charger ,
You can have converter (aka shore power charger) , solar, and even the engine running, and extension cord hooked to a portable battery charger
All at the same time, with no harm to anything
