That's what they are, status indicators for the WS (indoor console/display), T (thermo/hygro sensor outside), R (rain gauge), and WI (anemometer). They display full until the batteries get down to a low level then they display a couple bars. That is, they don't follow the batteries draining by removing a single bar every now and then, just stay full until the batteries will need replacement soon. I did not find any documentation with regard to these icons anywhere, just learned about them from experience.