Noticed for second time that the battery indicator was down to one purple bar. Car still started but seemed it was the ICE that was doing the work and the motor helping out now and then. Prius is used to drive to/from work (10-15 minutes) and sits rest of time. Most times display is green bars or mostly blue ones. Have noticed the MPG is getting crappier and crappier (35-40MPG) as though the ICE is on line most of time. Is this a concern that I should take it to Toyota for look see? Is this indication of a cell or two becoming reversed charged? Any combination of buttons and/or switches that will "magically" allow me to see on display whats really going on with big battery? I would rather spring for a new rebuild than be stranded "on a dark and stormy night".