Thank you @ton618, your answer was the most relevant and informative that I've found on this topic. I had a similar issue but the cause was different, so I'll explain here so others can benefit. My Canon 7D fell about two feet onto pavement. After that the camera would do nothing except show the blinking battery symbol on the top LCD. If a fully charged battery was left in overnight it would be dead by morning. I also have a 5Dii and a charger which shows charge level that I could use to verify the state of the battery. The cause was one of two (or both) things. First the power board (as described by @ton618 ) has a metal shield over it, top and bottom, presumably to shield the rest of the camera from the EMI that switching regulators will generate. Three edges of the top shield are held in place by very small clips on the PCB. That shield had escaped its clips from the shock of the drop and could have been shorting some components on the power board. Second, the power board is held in place by two screws...