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When you are plugged into power the power converter or inverter will charge the batteries. The first thing I would do is go to the batteries and follow the cables, look for a tripped breaker, below is a picture, some are thermal and self reset and others have a small tab on them that pops out when they trip. As a general rule they like to stick them 18" from the battery, could be on the frame OR in a battery control box with other fuses and breakers. IF you see any you can check voltage. You would check each post to chassis ground. The voltage should be the same across the posts. If one side has low voltage and the other high voltage then it is the issue.
Fleetwoods can be difficult, many will have both a power converter and inverter, the inverter would allow you to have AC power when you are not plugged in, a power converter will not do that. A power converter takes the AC voltage and makes the DC voltage it also charges the batteries, I am fairly certain on the units that have both an inverter and converter the converter will do the charging, most likely the converter will stand alone and plug into an outlet near the breaker panel, sometimes they are under the fridge, stove or behind the breaker panel. IF you know the make and model of the converter I might be able to help you some more. Please feel free to follow up if needed, IF you are satisfied with my efforts please feel free to select a rating, it is the only way I get credit... Robert