I have just arrived to lead a workshop in Berlin. The journey from Flekke was long and involved many stages. the last stage was a taxi from the airport to the hotel (I'm not good with undergrounds and trains). The taxi was a Toyota Prius, it's the first time I've ridden in a Hybrid and was mesmerised (good job I wasn't driving) by the dashboard display of the energy flow between the engine, battery and electric motor/dynamo. When motoring along energy goes from the battery to the motor then to the wheels and from the engine to the wheels but when braking energy goes from the wheels to the dynamo and back to the battery. I'm planning to make a multiple choice test based on different screen shots of the display. Lots of good physics here. One thing I don't get is why, on the animation shown, is the engine sending energy to the electric motor when the motor is not charging the battery.