Well first off let me welcome you to the Forums. It's always nice to have a new member. Next, when posting a problem it is imperative that you give some vital information. In this case knowing that you have a 2005, Minnie Winnie 26A, I was able to look on winnebagoind.com and find the Operators Manual for your rig. If you don't have the manual, you too can find it on the Winnebago web site and download it in a PDF format. If you do have it, I think you need to sit down and read all of it but you should pay particular attention to Section 9, Electrical. Not only will it tell you that you have a Battery Disconnect switch, it will show you a picture of it and it's location. You'll find that on page 9/7. It's called a Aux. Battery Switch.
The next thing you need is a DMM. That is a Digital Multi-Meter. They are available at HFT, Norther Tool, Lowes, Home Depot... Many under $20.
With the Aux, Sw. turned on and the engine running, touch the meter probes to the battery terminals. Red is positive and Black in negative. You should get a reading of 13.8 to 14.4 volts DC. Turn the engine off and the voltage will drop to about 12.7 VDC. That will tell you that your engine alternator is charging both the chassis and house batteries.
On shore power or generator power, the charge rate will be given in the manual for your Converter.
When your done reading the owners manual, search for The 12 Volt Side Of Life 1 & 2. Read them.
At that time you should be well on your way to being an knowledgeable RVer. Good luck and Happy Camping.