Originally Posted by mondofromredondo
I've installed new AGM batteries as well as a Xantrex Smart charger.
I'm concerned that the voltage regulator on my 1988 35 hp Yanmar is not suitable for the AGM's.
Could this be true? Should I be replacing this older regulator with a smart regulator? Sometimes I motor 6 or 7 hours so I'd be concerned that I am overcharging my batteries.
What are the voltages you are seeing at the batteries:
Battery voltage just after start up?
Battery voltage after 30 minutes under loaded charging?
Battery voltage after one hour under loaded charging?
Battery voltage after two hours under loaded charging?
Battery voltage when the bank is known 100% full?
Most of the Hitachi alts temp compensate and reduce voltage as they heat up. This tends to lead to chronic under charging, not over charging. Monitor your voltage at the batteries under the situations above and let us know what you find.
Any factory alt where the voltage regulator reduces the voltage based on alternator temperature, such as many of the Hitachi alternators found on Yanmar engines, is one that is not doing you much good trying to charge a large or demanding bank like AGM batteries.