Safe to charge battery while connected to shore power

In my old fiver, if we were boondocking and needed to get a quick charge to the battery, I'd use the battery disconnect switch to isolate the battery from the onboard converter, then directly attach my Sears intelligent battery charger running off the genny. Would move that Group 31 from 40% to 90% in less than an hour. Got a smarter charger in our current rig, so haven't had to go that direction since.