Every Coach that I've had the lights and some appliance control are power by the coach batteries. The battery charger or like mine charger/inverter keep the batteries charged when the voltage drops to a certain level. The more cycles you do the faster you wear them out. The more batteries you have the more power you have in amp-hours the less cycles you have. My Coach can go almost all weekend without charging the batteries. So you may not need that many but its what manufacturer thought your coach needed with the amount of potential loads on the.
I hope this helps.
