Thanks for the explanation,folks!
Didn't mean to hijack the thread but have a similar situation in our Shadow Cruiser pop top slide in camper-dorm fridge that runs off inverter during transit and is physically unplugged from inverter and into an extension cord when on shore power. In my case the onboard converter is bad and dosent charge the battery. Charging is accomplished with either a portable charger or heavy duty alternator wiring.
That leaves me either dealing with the charger or an extension cord for the fridge.
Usually there is no need of the charger as the alt keeps us charged till we stop.
Thanks,Mike