[saalweachter]

I'm not actually sure how many plug-in hybrids go for an all-electric power train, versus a dual power train.

I know the Chevy Volt had an all-electric power train, and the ICE is purely a generator that dumps power into the electrical system, and the Chrysler Pacifica Hybrid has a dual power train, but I wasn't able to find a concise list of which hybrids have taken what strategy.

[genewitch]

parallel versus series hybrid. Series will have ICE generate and the only thing attached to the wheels is electric motors. Parallel (like the prius) the electric motor and the ICE are connected to the wheels. There are reasons for both, but freight trains in the US are series. In my opinion, series is probably the best, since you can engineer the ICE to be as clean and efficient as possible at exactly 1 RPM setting - making them last longer to boot.

I apologize for forgetting the benefits of parallel hybrid systems, but i know there are some, including needing a smaller ICE, all things equal.