ALL batteries read as "empty" (flashing icon on top LCD).
Testo:
I can't find anyone with a solid solution online.
Batteries that and confirmed to be good and charged will read as empty and my 5D mk II will not operate. Nothing on the rear LCD screen. Only a blinking empty battery on the top LCD. The top LCD comes to life and responds to settings changes (wheel to change aperture or shutter speed) for a second before becoming unresponsive and blinking the empty battery icon. I've replaced the internal "watch" battery.