13.6 sounds about right. That's what I see when I check the voltage while plugged into shore power. My Shamrock comes with a WFCO 3-stage converter and the three modes/stages of operation include (
shamelessly copied from the manual):
Absorption Mode: During this mode, the converter output is in the
13.6 Vdc range. This is the normal operation mode. This mode
provides the 12 Vdc and current required by the 12 Vdc RV appliances,
as well as slow charging the battery.
Bulk Mode: When the converter senses that the RV system voltage is
less than 13.2 Vdc (equivalent to less than 50% of battery charge) the
converter will automatically go into the “Bulk mode.” In this mode, the
output voltage of the converter will switch to 14.4 Vdc for a maximum
of four hours.
Float Mode: If the RV is not being used for approximately 48 hours,
with a “no load” condition and the shore power is plugged in, the
converter will automatically go in to the “Float mode.” In this mode,
the converter is charging the battery with a trickle voltage of 13.2 Vdc.
When the converter senses a demand (by turning on lights), the
converter automatically returns to the “Absorption mode” 13.6 Vdc.
By the way, the 14.4volt limit is why I also use a battery charger occasionally. The two Trojans I have need 14.8 volts.