Oh, I didn't realize that after you install a widget, it does nothing. The N7 guide doesn't say what a widget is -- it is a word with no meaning to me. The guide says how to put a widget on your home page, but after installation I thought that the battery widget *was* on my home page. Sigh, ir did nothing. Now I got it working -- only took three days.
With my phone, when it is turned off and is charging, I can touch the screen and see if it is finished charging, so I thought the N7 might have something similar. But I guess it doesn't