IMPORTANT: Fix For Battery Problem
I was having a problem that I thought was due to the poor quality of the batteries, including the Canon battery. After I had used the camera for time it seemed the batteries were not holding their charge, then it got tot he point where when I put in a fully re-charged battery the camera would start, shut off immediately and tell me the batteries need to be charged. However, when I put the battery in the camera the green light came on almost immediately, telling me the battery was already charged.
My problem was that after a period of time using the camera that the batteries seemed to lose much of their charge. Then not even a fully re-charged battery would work. The charger by means of the green light was saying the batteries were charged. However, the camera would start then shut off immediately saying on the screen that the batteries needed to be charged.
Yesterday I contacted Canon service and received a quick response. The fix, they said, was to remove the battery from the camera, CLOSE the battery door, then press and hold the start button for 1 minute. At the end of the minute, I opened the door, put in the battery, one of those the camera had been saying needed to be charged even though the charger said it was charged, and pressed the start button. This time when the camera started I could see on the screen that the camera considered the battery fully charged. What a relief!
Canon said that what happens is that sometimes the camera's capacitor (whatever that is) retains some of the energy, causing the symptoms that I was experiencing. Removing the battery,closing the battery compartment door, and pressing the start button for 1 minute drains all the energy out of the camera and resets the camera.
I asked whether it was possible that I will have to do this again, the reply was "yes", it is very possible because they don't yet know the cause.