I've added a drain rate overlay to the battery applet which can be seen here.

To install you will need to run asui uu; asui dt; asui it; asui da to upgrade the convenience script, install test binary and the statusbar test applet. Then restart statusbar applet.

What do you think of the icons? Have a better idea for them?

Since green is used for the charging icon I combined ASUI's green and gray into a single gray overlay and added an additional transition at 2.0 since maacruz suggested 4 colors. What do you think of these transition points, should the transition to orange be higher than 2.0?