Navigon- Can't hear radio with USB connected

Hello Everyone! I am new here.

I recently splurged for Navigon for my new Iphone 4S. Only problem, I like to listen to the XM radio, AND hear the voice turn-by-turn directions. I can hear them fine, IF the phone is NOT connected to my USB charger cable in the glovebox. However, once I attach cable, I only have access to what is streaming through my iPhone. However, I need to charge my phone while using the nav, as it eats up the battery like crazy!

If I purchase a "cigarette" adapter charger, would I be still able to hear the voice prompts, through my iPHONE SPEAKERS, while still using my radio??? (I have a 2011 Honda Odyssey with Bluetooth.) In other words, I want the Navigon app to be completely separate from my car's sound system. I have used the Waze app, and it manages what I need! However, I like to have a Nav app that doesn't use data if possible.

Thanks so much,
Joan

Thank you for your answer.

I was thinking the same thing. I've confirmed that it will work with the home charger attached. I was trying to avoid buying another charger- as the USB has been working well for me in that capacity.

I will test this out & report back. I'm just curious if most folks avoid the "radio," or are they charging with a "cigarette" power adapter/ not USB.

Good idea, but I am trying to avoid "data" charges, as I'm on the 200mb AT&T plan!

This is the reason I chose Navigon, since it doesn't need the data connection.

Mystery Solved!

I bought a power adapter charger for the car, and now everything works perfectly.

Thank you to everyone that got me on the right track.