Not enough information. I wonder why kids write is a telegraphic way assuming we can figure out the rest. I went to one of my cars and read the car manual. The red battery shaped light in the dash means the battery is THE only source of power to the car. By turning the key to ON, many lights self test and go out. Several stay ON and one of them is the battery icon. When the alternator is running, courtesy of the engine running, it powers the car and recharges the battery. This light DOES NOT mean that there is anything wrong with the battery. DOES NOT. There is ONLY ONE purpose. To indicate the battery is powering the electrical system. That points to the alternator not doing its job. I suggest you contact a mechanic.

When the battery light comes,the battery cables are loose or corroded at the battery,engine block,or starter.OR the battery is low on charge.OR the alternater isn't working properly.The battery should have 12.6volts or higher when its fully charged.If it has 9.6volts or less,it doesn't have enough capacity to start the vehicle so get it tested at Autozone.It might just be low on charge or it might have a dead cell.Here's a good article to read through about the alternater.

http://auto.howstuffworks.com/alternator...

Either your belt that drives the alternator broke or slipped off, or your battery or alternator (or both) have crapped out.

It is most likely cause by a bad battery or a bad alternator. Here is how to test your alternator yourself (really easy):