Why would the ICE be running at all when the battery is totally charged to point of being green after a long descent and I am continuing down a further gentle slope at about 20-30 mph? This just started this week with the warmer weather. Before, the ICE did not come on. I am driving a new Prius that I purchased at the beginning of March so I am still learning about the vehicle. Is the battery so fully charged that the ICE has to come on to cool it or something? Nothing else is on to draw current from the battery.