Battery Cover stuck on Magic Mouse
Experienced this problem that others have had but could not reply to the thread.
A solution to this problem (when the battery cover will not open to allow for replacement batteries) is to use a pen knife and place it next to the black 'slider strip' near the apple logo. Next press the blade toward the side of the mouse. That action will bow the removable panel up and allow you to pop it off.
My mouse had corroded that had adhered the batteries to the cover. I removed the batteries and scratched away as much corrosion from the cover as possible. Small bit need to the removed from battery posts as well. Mouse back up and working.
Just thought this may help others.