IT WORKS!

        Right after posting the brief item about the easy battery test, my mouse battery went dead! I immediately got a new battery and tried the test. It worked!
        The two batteries performed exactly as the video said they would. Don't ask me how it works, but it does! I wish I had known about this years ago.
        Here's the link again: battery test.
        PS It would make a nice parlor trick to show those who don't know it. Eg., "I have three identical AA batteries in my hand. One of theme is dead, and two are good. I bet you I can pick out the dead one without using a tester or inserting them in any kind of gadget."