Alternator charging

[A Rooney]

Just curious,on my manual for my 2001premier,I noticed that the coach batteries disconnect switch does not prevent the alternator from charging the coach batteries,If the converter doesn't stop charging a fully charged battery it has a breaker,However what prevents the alternator from overcharging and damaging a battery?The solenoid protects the engine battery,and the lvd,prevents damage due to low voltage,but I am confused as to what stops the alternator?,I noticed on my new fully charged batteries that the alternator was throwing a 13.8 v charge at idle on them?

[Manitou]

Good question. I dint know electrical enough to explain, but wouldn't the same problem exist for the chassis engine battery? Something must control the overcharge.. Not sure how/what.