I have a 2009 Prius..when I am stopped for a train I noticed in a little while that my battery indicator goes down to purple area and my ICE starts up to recharge it..it takes a few minutes to go back to blue but it discharges faster with the headlights and a/c on...is that normal? I thought the 12 volt battery helps with accessories and I have replaced it a month ago. When I start driving it will quickly charge up and slowly go down as it is needed. Most of the times in the green area.
12V battery is charged from hybrid battery. So all the energy that you use from 12V system comes from hybrid battery if Prius is in Ready and engine isn't running. AC uses energy from hybrid battery directly so that makes the hybrid battery bars go down even faster. So that's all normal. But if your hybrid battery goes down faster than normal and then charges up faster than normal that probably means it's starting to go bad.
