the battery indicator is constantly on and the camera just shuts down. what can i do?

changed the batteries dont know what else to try.

Chances are, you're either not using recommended batteries or the batteries you're using are simply underpowered. You don't have to use Canon brand batteries, mind you, just the type of batteries Canon recommends. And the mAh needs to be at least 2500.

Also, I'd clean your battery contacts. They can get dirty over time and that dirt can cause connectivity issues with the batteries. A good cleaning with a pencil eraser should do the trick.

Lastly, you should get into the habit of checking the Canon website every so often for firmware updates. The firmware is only as up to date as the day the camera was built and chances are, a firmware update has been released which addresses issues which may have cropped up since then.

Hope that helps.