I know I'm late to the party, but I haven't seen any threads on this. In ACC mode if you only have the radio on (headlights off w/parking brake, MFD off) everything is just on the 12V. However, if you put on the running lights, the HV battery fan blower kicks in. When you turn on the headlights you can hear the inverter pump turn on. I guess it might be obvious to people. I often wonder after a long drive if it would be beneficial to leave the inv pump or battery fan running. But I guess that thinking like an ICE that still has a lot of heat when you shut it off. Whereas the inverter stops making new heat immediately. I suspect the battery fan should run on a really hot day after you shut it off but I doubt it, they seem to have made everything drain-battery-proof of the Gen 1, even going so far as to remove a trunk light. This is possibly related: Yahoo! Groups
This is interesting indeed. However, I have taken my Prius on many 28-32 hour trips to florida from Canada driving straight, and I can assure you that it takes a long trip as well as any other car. My only wish is these accursed torture devices they call seats could be much more comfortable. The Toyota iQ has thinner seats but is miles more comfortable. At any rate, when I get a chance, I will look into this myself. There could be some benefit, and perhaps if the behaviour is consistent, then you may have helped develop a test parameter for those of us whose battery fan has failed.
At least the 2003 if you are in ACC (ie. radio only) and put on the running lights, you will hear the HV battery fan. I'm pretty sure it always works though I haven't tried in below 50 degree weather.
