I believe if the traction battery dies, there is no power to available to make MG1 spin and then the gasoline engine cannot be started. Which means, no, the car will not run w/o the hybrid (traction) battery.
No, it won't. No way to start the ICE without the traction battery, as it is spun by MG1 (as others stated before me).
I also believe that without power to MG1 or MG2, the ICE will be in neutral and unable to move the car. It needs to push against something, as it is not directly attached to the wheels. A simulation of Prius's Planetary Gear
Jimbo, Thanks for that planetary gear sim. cool. Regarding the original question, all above is correct and the only thing I would add is the fact that without a traction battery, the system will have DTC's up the yingyang, and will probably disable the car from even moving. You'd be lucky if you would even able to get it out of park in that situation...just my 2c.
My SWAG is that, no, the car will NOT run if the hybrid battery is COMPLETELY DEAD. The system REQUIRES the battery to provide power in even low load situations to provide torque to MG1 while the engine spins. I could be wrong, but the system works by balancing torque, and sometimes MG1 gets driven (generating power) and sometimes it has to push, too.
