Chinook RV

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?

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.