Sorry, my mistake. The holding battery charge is 12.7V, not 12.4. The 12.7V is the holding voltage about 3 hours after the daily top-up charge has been completed.
One battery is a lead acid deep cycle (for the auxiliary items and lighting) Century 12V 102Ah Deep Cycle Flooded Battery(N70T)and the other is a SuperCharge SeaMaster Gold Marine MF(MFM70) lead acid cranking battery used for nothing other than motor cranking. The deep cycle is charged from the cranking battery through a Voltage Sensitive relay. I plug on a Repco 12V 4.3 A battery charger, which has a full charge cut-out, to the cranking battery.