BF,
Both of my previous Interstate AGMs (built by C&D Technologies) said on their labels to use 14.X volts for Cycle Service recharging and my current Fullriver AGMs recommend the same for Cycle Service recharging.
NOWHERE, have I found in writing - electro chemically - an explanation of how AGM batteries are ruined by using less than 14.X volts for recharging. They MUST be periodically fully recharged however - which I use a built-in ammeter and a lot of time at 13.8 volts and a little time at alternator voltages to do.
Liquid lead acid batteries are of course another story. Stirring of their liquid (bubbling during charging due to using high enough voltage) makes a lot of sense in order to periodically restore uniformity of their liquid's chemical makeup. Plus, probably other chemical reactions at their plate-liquid interfaces are needed to restore plate surfaces eroded by the battery liquid over time ... and periodic higher recharge voltage may drive these reactions.
