Yes you can plug your RV into electric at an RV park and your RV's Converter will take over the job of providing 12 volt power to your RV's 12 volt accessories and of course you will also have 120 Volt AC power since you are plugged in.
One thing you should be aware of is that when you plug your RV into electric your RV's Converter is going to try to charge your House Batteries. Whether your House Batteries are good or not you should make sure that they are full of electrolytes. If your batteries are low on electrolytes, you need to top them off using distilled water only.
I strongly suggest that you get the batteries replaced as soon as possible. Your RV's electrical system is designed to have functioning house batteries and although you can plug your RV in with bad batteries it is not a good practice to do this continually.
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