the only type of battery I can think of that has power output issues would be a small number of conventional lithium-ion cells.
So, why does Fisker require you to start the ICE to get full power output from the eMotor?
Tesla is talking about Whitestar having even more eMotor power than the Roadster, yet they are talking about a REEV version with a much smaller (and less expensive) battery pack. I do think that battery power output capability could be an issue here.
Tesla is trying to use inexpensive commodity laptop cells (in large quantities). Sure you could get expensive cells with higher "power density", but they are trying to find solutions that use more "run of the mill" batteries.
I don't think my idea of running the ICE while the pack still has a lot of charge left is unfounded. I think we might see more applications designed to work that way. Letting the pack run to near empty before starting the ICE sounds good from a marketing standpoint, and works in an "ideal world" situation where people don't ever drive more than 40 miles between plugs, but I don't think that will work for everyone.
Does the mainstream want a "mock EV" that lugs around a big ICE generator for those days when you go over your BEV limit, or do they want a well engineered Hybrid that does use some gas, but with significant battery assist, and plug in capability they get effectively over 100 MPG?
I guess we will see which wins... The series PHEV Volt or the next gen PHEV Prius. If people only ever drive short distances, and always plug in long enough then the Volt may be the winner. If people do drive more than 40 miles frequently, or neglect to plug in sometimes then the Prius approach may end up with the higher effective MPG numbers.