Vehicle charging systems have a complicated job even before connecting RV batteries, solar panels and generators. For starters, how can the computer know the state of charge of the engine battery; without that it cannot set an appropriate alternator voltage and must default to a too low but safe voltage. There ought to be an amp-hour counter on the battery to inform the computer of its state of charge. Then my vehicle that mostly does a km or two between starts could enjoy intensive charging to make up the loss of charge to frequent starting.
With all the potential RV sources, batteries and loads the best policy might be for all sources to attempt to provide a fixed high voltage and for loads and batteries to take what they need via voltage regulation and battery charge controllers.
Maybe the whole system design will be refreshed when vehicles move to 24 volts or higher.
