You didn't say what exactly you have, so I will tell you what I did.
You can apply it to your circumstances.
My coach has 120v outlets supplied by 4 8D batteries and an inverter/charger.
It is configured so that shore current or generator run through the inverter/charger or battery, whichever power source is called upon/required.
I pondered your question and initially thought of hooking directly to the battery.
The downside of that was that the batteries were not conveniently close to the radio installation point, so I added a 35 amp power supply to an 120v outlet found in the radio install location.
Until I tried the my setup I had no idea if it would be "quiet or noisy" with some luck I find it very quiet and am happy with the results.
What ever you do be sure to fuse both leads .
JIM