You've got two things that are controlled by the panel:
1. Convertor: this turns A/C (shore power or the Generator) into 12v, and charges your batteries.
2. Inverter: This turns your 12v batteries into 110v A/C to power your tv, or other standard "house-plug" items from your batteries. You can turn this on and off at the control panel, but be aware that it only powers some of the outlets....not all of them. It also won't provide enough power to run your roof air conditioners or microwave.
When you are plugged into shore power, your batteries will be charging no matter if the Inverter is on or off. In fact, if you plug in, and use the electronic battery disconnect by the inside door light switches, or even turn the manual battery disconnect in your battery bay, the batteries will still charge.
That is, if you have good batteries. If they've not been taken care of, batteries will go bad, and not take or hold a charge.
On your control panel you should see at least three different charging status: bulk, float, and absorb. Check the Magnum manual, or give magnum a call for a deeper explanation...they've been very helpful!