AC Converter switch? What does it do?

[aquadancer]

My routine - AC converter always on when connected to shorepower or running generator at anchor. AC Converter off when engines are running as alternators will charge batteries. Never had issues cooking batteries, either regular flooded lead-cell or AGM.

 

[dpmulvey]

Leave it on. Many Sea Ray's have isolators to preclude overcharging.

 

[comsnark]

If the boat is kept in the water, best to leave it on all the time. Should a hose or clamp fail, or something else begin to leak, your bilge pumps will run the battery down in short order and down she goes...
Lots of boats sink at the dock from nothing more than rainwater because the owner didn't have a charger or it wasn't on.

I have heard the advice to turn off the converter AND the battery switches. It sounds nuts for the exact reasons stated here.

I would rather risk fried batteries than risk sinking the boat.

Once, when picking the boat up after being in the shop for a several days, I asked the shop to turn on the Fridge for me. . as I wanted a cold fridge to put drinks into when I arrived. They *would not*. I pleaded. They simply would not. Geez.

I left the converter off for a few weeks, with light use on the boat, and noted that my house batteries/port engine battery (they are in parrallel) were weak after several weeks. Turning the inverter back on fixed the problem.