I did it a little differently:
(.gifs above are only 10 of the 20 images each.)
I basically took the label for the charge percentage, stripped the percent sign, and evaluated that into a slider. For the charging symbol, I used the RRStrings plugin to evaluate the length of the label, if it's 8 (Charging) it displays a charge symbol, if it's 11 (Discharging) or anything else, it displays nothing. I did it this way so that I could use one set of images for the battery whether it were charging or not.
A normal indicator would be nice. A simple true/false kind of thing...