Truck says battery need charged but it's fine?

I drive an avalanche and we have this little screen that say your mileage, how many miles you have and buckle seatbeat, etc. But my check engine light recently came up, I don't know if it has anything to do with it but While backing out of my drive way I realized something wasn't right. I cranked it before I backed out and as soon as I got out i couldnt hear my exhaust. I look at the little screen and it says battery not charging. Im retarded when it comes to these things. what could be the possibilities.