Re: Alternator sizes
Alternator size is determined by the unit output in voltage and amperage. But another factor is to be considered. The charging factor to be considered is the charging time. Most high output alternators are expensive, large and difficult to remove and replace. Usually a 125 amp alternator will do a great job of keeping a battery bank charged and powering a AC unit. In my Crown bus, there is a single prestolite 125 amp alternator and several 12/120 inverters. My battery bank is just a pair of Walmart 950 cca batteries. A charging system with a 125 amp alternator will recharge any battery bank easily and as well as a 200 amp alternator, but takes a little more time. Mostly the time factor is not important. Usually large frame alternators have large bearings and last longer.
The most important factor in any wiring is wire size and good firm connections. I prefer using a 100% duty cycle relay to manipulate electrical power. There are many good relay available. Frank in Idaho