battery warning in gauge above steering wheel? what does this mean. is it related to the car battery or key battery? has been happening for 2 weeks, no problems with car at all so far. sensor on actual battery is green.

 

its in the shop now. 2007 MCS with 23,000 miles and it looks like the alternator has failed. is this common?

 

Not common, but also not unheard of. Electrical parts can go any time. It could have lasted longer than the car, or it could have died the day you drove it off the lot.