Anyone's battery ever go PURPLE?

Keep in mind that there are actually two motor/generators. When you're driving up hills it is common to see both the ICE and the electric motor providing power to the wheels, and no power going to or from the battery. In this balanced state, MG1 is generating power and sending it directly to MG2 to help drive the wheels. This is also a more efficient situation because the inverter is not being used and therefore there are no conversion losses.

 

Thanks, that is something I hadn't thought of. The car is way more sophisticated than I give it credit for.

 

Actually, the inverter is being used. Each motor has its own set of power FET transistors connected to a 500V bidirectional power supply. Each motor is a 3 phase AC syncronous motor. Only if they were operating at the exact same speed and phase would it be possible for the inverter to not be in the picture. In the scenario where MG1 powers MG2 without help from the battery, MG1 maintains 500V charge on the 500V capacitor, and MG2 uses that charge.