Traingle means

Got a red triangle on dash. 12 volt was dead. AAA recharged it red triangle still on. Why?

I had written a much better explanation but it took me 1/2 hour to write slow typist. I then went to submit it and pop up box tells me I need a title which I put in. Another pop up gives suggestions to look at but none match mine. When I went back to mine all my 1/2 hour work was gone. It left me very angry that the board software doesn't leave your original alone. Thus my opening terse sentence above. I am not spending another half hour of my life retyping.

So what does a red triangle with exclamation mean? Is it a fatal problem?