What will happen to my VRLA DRY CELL AGM or GEL battery's life if the charge voltage is not controlled?

You will reduce the life of your battery by between 5% and 7% for every 1/10th of a volt above the recommended charge voltage. For example, suppose you continually charge your battery at a temperature-compensated value of 14.60 volts when it should be at 14.20 volts (4-tenths over). In that case, you can expect to reduce the life expectancy of your battery by 20% to 30%.

As mentioned, VRLA DRY CELL AGM and GEL batteries are voltage sensitive. All batteries are voltage sensitive. If you continually charge your VRLA DRY CELL AGM or GEL battery over the recommended voltage levels, you will shorten the life of your battery.