Still not sure what a converter rating is based on. Is it the total DC load in an RV, recharge time or total battery capacity, or all?
The rating is a fixed output because of the design of the charger. I think you may be referring to choice of size.
Ideally, the converter should charge the battery(s) in a short amount of time to 90% of capacity. It may be that a user also has large amperage loads that are drawn while the battery is charging. Sizing would take into consideration those loads, especially if battery capacity is also increased to address the loads. For example: while running the V;air compressor for an hour and using other devices in the trailer, simultaneously, that hour of usage could maybe draw 40 AH from your battery. That might be close to 50% of a 100AH AGM battery. At that point, you would wish to recharge your battery to 90%. A 55 amp charger would get you there in 2-3Hrs, most likely. If you were a user that needs to power the converter on a generator, you might wish to upsize your converter rating to chop some generator run time. FWIW, I've found that most AGM batteries will suck up those amps from the charger quickly. You may get by with less charging time with AGM's.
