Sounds to me that there may be another battery inside the camera that is going bad.
Everytime I power on the camera the Date / Time needs to be set.
Replacing the Date Battery for the PowerShot A480.
Replacing the Date Battery.
If the Date/Time menu appears when the camera power is turned on, the date battery charge is low and the date and time settings have been lost. Please purchase a lithium coin battery (CR1220) and replace it as follows.
Please note that the first date battery may appear to expire relatively quickly after you purchase the camera. This is because it is installed in the camera at the point of manufacture, not when you make the purchase.
Be particularly careful to keep the date batteries out of the reach of children. Seek medical assistance immediately if a child swallows a battery since corrosive battery fluids can damage the stomach or intestinal walls.
1. Confirm that the camera power is turned off.
2. Open up the battery door / cover and remove the AA Batteries.
3. Remove the date/time battery holder.
4. Grasp the battery and slide it in the direction of the arrow.
5. Insert a new battery with the (+) side facing up.
6. Replace the battery holder and battery cover.
7. When the Date/Time menu appears set the date and time.
After purchasing the camera and turning on the power for the first time, although the Date/Time menu will appear, you do not need to replace the date battery.
If you ever dispose of your camera, first remove the date battery for recycling according to the recycling system of your area.