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This looks like a great setup.
You are dealing with a lot of solar power here, with 900W. So you’ll need a good quality charge controller.
I would suggest a MPPT controller that can easily handle the maximum amount the solar panels will generate.
Leave another 20% of headroom on the solar panels. So if they suggest 900W output from the panels, get a controller that can handle 1,080W. Mount the controller so that it has lots of air circulation for cooling. Ensure you use cable that is thick enough to avoid voltage drop.
Some info on PWM and MPPT controllers.
“The PWM controller is in essence a switch that connects a solar array to the battery. The result is that
the voltage of the array will be pulled down to near that of the battery.
The MPPT controller is more sophisticated (and more expensive): it will adjust its input voltage to
harvest the maximum power from the solar array and then transform this power to supply the
varying voltage requirement of the battery plus load. Thus, it essentially decouples the array and
battery voltages so that there can be, for example, a 12 volt battery on”
You don’t need to consider the alternator very much.
When the engine is running and the alternator will be generating about 14 volts.
The solar controller will sense this and it will not attempt to charge the batteries as it will consider them full.
Only when the engine stops, and the voltage drops to 12.7 (or so) will the solar controller attempt to top-up the batteries again.