I have a second alternator on the "new Crown". With the Cummins big cam in my bus there were unused V belt pulley positions on the main pulley already used to drive the original alternator. My son modified the alternator mount to provide for side by side mounting of the alternators, with staggered mounting, thus allowing the second alternator to be driven from the next two pulleys. It is easy to get to and get good airflow to keep them cool. The second alternator is rated for 250 amps.
The bus has a 65 amp RV charger and will have solar to also keep up the batteries. The bus electrical is kept separate to assure that RV needs never make the buys batteries dead.