Should batteries be disconnected when on shore power?

06Fargo wrote:
My rvs have Intellipower something or other converter chargers with fancy battery charging...

Or do the batteries provide a "cushion" for starting 12v furnace motors etc.?

Details are important. "Something or other" just won't cut it for a question like this.

And I don't understand that second question. Typically things like furnace motors run off 12 V which comes ONLY from the batteries when shore power is not connected.