Getting change the batteries error

It's usually dirty battery terminals (usually negative), or battery corrosion when this occurs. In most cases it can be repaired by cleaning the contacts (use a Q-Tip and get the positive ones inside for good measure as well) with something like isopropyl alcohol (99% preferred, but 97% works). That may be enough to fix it, but if that doesn't help then you need to use something like denatured alcohol.

If neither of those works, you need a new battery cover. The issue there is you end up having to find a donor camera due to the high cost of the parts on what is a common commodity P&S camera, which kills the economics of the repair. I had to abandon my SX150IS due to the repair cost to replace a damaged front panel, and donors often have THE SAME PROBLEM!

If that doesn't work, try better batteries. My general recommendation for devices like this is the Panasonic Eleloop Pros. They’re pricey but are designed for this type of application, but are cheaper than primary lithiums. However they aren’t as good with regard to runtime.

EOL WARNING: THE CATCH WITH CANON'S 2X AA BATTERY CAMERAS IS IT TENDS TO POINT TO A BOARD FAILURE AT THE COMPONENT LEVEL WHEN NOTHING ELSE HELPS :-(! Save the "dead" cells, as they will run other devices for a while.

This fix is to get a bit more time out of a dying camera that is confirmed to have a terminal failure which cannot be repaired economically. DO NOT USE IT FOR NE CRITICAL SHOOTS IF THIS IS THE ONLY SOLUTION THAT HELPS! Enjoy the extra time, and say goodbye to the camera when it completely fails. You may want to have a new one alongside the failing camera in case it kicks completely.

The specific issue is the main board in these cameras are beginning to have component level issues with power management, and the time required to properly repair the fault costs more in time and labor then it costs to replace the cameras.

These kinds of problems are why the "AA" battery camera is dead; it's all about 6V Li-On rechargeable batteries today because they don't suddenly have hard failures like this where nothing can be done economically. At least with the modern ones which did away with this fatal failure point found on the 150/160, I can recycle the battery and probably revive the camera with a new battery!