I was pleasantly surprised yesterday when there was a message on the screen that the battery in the key fob was low; I didn't know that the car was going to alert me. So, I got out my backup key fob today and drove to the battery store to have them replace the battery in the first unit. When I turned off the car it warned me again that the battery was low in key fob I hadn't been using. Seems like the key fobs are identically programmed and so the car couldn't detect that I was carrying two...? Just wondering...