I'm with Jonathan - Randy @ Best is the one to talk too - he steered me in the right direction when I replaced the old Univolt...
I recently added the Voltminder that they sell - it has an adjustable low voltage alarm that you can set to warn you when your battery charge level (voltage) is becoming low, so you can 'shut er' down' or go out and fire up the trusty red Honda Genny...
I opted for the 45 amp converter/charger, as we had only the two batteries...I've since added another battery, and now wish I'd gone with the 55 amp unit - However, the 45 amp unit seems up to the job of recharging our batteries in reasonable time when we're out in the boonies...
We've gone to all LED lights in our AS, inside and out, so the 'lighting' load isn't all that bad, and we're really only recharging the batteries for the use of the Sat TV or DVD at night, the fantastic fans when it's warm, and the water pump upon occasion...
I've found a long time ago, that it's best to fire up the Genny for a short period EVERY day when you're off the grid, to insure the batteries don't get to low - it you let em' go too long and get discharged completely, you'll find you need hours and hours to get em' back up to snuff...a little charge a day is best...
Enjoy...
Ray