One of the things that I monitor with my OBDII ScanGauge is charging voltage. On my coach, both the house and chassis batteries are charged by the alternator when the engine is running. As I drive down the road, my charging voltage can get as high as 14.6 volts during normal operation. This has not hurt my flooded wet cell chassis battery or my four 6 volt gel cell house batteries which are all going on 6 years old.
When parked, my Xantrex has been configured for the gel cells to keep them charged and my chassis battery is hooked up to a DelTran Battery Tender to maintain a full charge.