Skip,
What you need to do is find the unit's converter/charger and get the manufacturer, model and number off it. Then, look it up on line and see if it is a three or four stage job. If it is a modern smart charger, they batteries will actually last longer because of the conditioning that they will get.
If you can't fine it on line, comeback here and someone is likely to know it. The we can give you a solid answer.
When you come back, tell us what the house bank is or what you want it to be. You don't want a number that has the potential to over heat the bank when recovering it from a deep discharge.
Matt