We have an 02 Adventurer and found that since June when everything was working great that our batteries are toast too. FYI, somewhere about 11VDC the panel shuts off the batteries at the disconnect. I would use a good charger and try recharging the batteries before doing anything else. If like mine they just go up in the 12 Volt range and then drain down fairly quick, your out of luck. If they hold in the +13 volt range your ok but watch them as if it happens again it will damage your batteries.
Personally, I would open the battery compartment and lift the cables off the batteries and do the charging. If you have a meter, not test light, after the charge is complete read everything and then after a few hours reconnect the batteries and read them and compare to the meter in the All In One panel, should be in the 13 volt range.
The converter, probably under the fridge, is where the 120 VAC is converted to 12VDC. This is where the cables to charge your batteries while on shore power start.
Charging from the engine alternator is via a devise commonly called a BIRD. Bi Directional Relay Delay. This selects when it is time to charge the chassis and or house batteries. Hopefully you have a diagram of the bird and how it works. It will show where the Bird is connected to the battery disconnect relays. You can Google Intellitec BIRD.
It's all really simple after you look at the drawings and read the directions.
With the house and chassis batteries fully charged, turn on the engine and using either the All In One meter read the voltages being supplied to the batteries. The should read like the users instructions say.