Dual power source

[amgen]

Robert,
Generally for lead acid batteries, the charge ranges from 100% to 0% as the voltage falls from 12.7 down to 10.5......in that range. --see chart--
So from experience, if you charge and maintain the voltage at 13 to 13.5 volts, that's a fully charged battery, and not overcharged...and when you charge up to 14.5 volts, that's kind of stressing the battery over time and will reduce the life of the battery.
So, if you were to set the voltage from the regulator to say 13.8 to 14, the diode drops .3 or .6 volts depending on the diode type, and you will maintain the battery voltage to a fully charged and not overcharged state continuously.

don