I've never quite understood this. Why not have the gas engine simply drive a generator which charges the batteries / drives the electric motors, like a diesel-electric locomotive? Then there's no dual drivetrain issue.

Even for an all-electric car, it'd be nice to have a small gas engine to drive a generator to charge the batteries if you're too far from a socket.

I work at a train museum. Locomotives are fundamentally different. They have to have electric traction motors to grab the rails. Weight is unimportant. 125 tons. That's a quarter million pounds, 113,400 kg. Automobiles need every weight-saving trick the engineers can pull off. Such as combination drives.

Also trains don't change speed super often so they can have their prime mover running in the power band all of the time. A car changes speed at lot so its more inefficient to have the prime mover running in its power band constantly to drive the generator.

This is one of the functions of the Chevy Volt - "...its internal combustion engine powers an electric generator to extend the vehicle's range as needed. When the engine is running it may be periodically mechanically linked (by a clutch) to a planetary gear set, and hence the output drive axle, to improve energy efficiency." -- from wikipedia page on the Volt

Yeah, I'd love to know why this hasn't been an option. Seems like the best of both worlds

It is worth pointing out that the Toyota Prius, despite being a hybrid, is regularly featured as one of the most reliable cars out there, including regular ICE cars.

Meh? I mean I've owned many cars over the last 15 years or so and it's never been the ice/transmission/drivetrain that's failed.

Meanwhile every car I've ever had has suffered from window motor failure.

FWIW, extra complexity and complicated transmissions can be largely avoid with the "range extended EV" approach, where the gas engine is a generator producing electricity and doesn't drive the wheels directly.

That said, the best vehicle in that style that I can think of, the Chevy Volt, does actually allow the engine to drive the wheels and has two planetary gear/clutch systems. On the plus side, the gas engine is expected to need much less maintenance than a regular engine that's used in a much wider power range.

You want the BMW i3 with range extender, the gasoline engine only attaches to a generator.

benefits to who? the best thing for the car buyer is a standard ICE car - every mechanic out there can fix it. the worst thing out there for the consumer is an electric car that can only be fixed by the dealer

That's a great argument against every new technology in a car. For example, only a subset of body shops can do aluminum.

How are you going to get gas, when the rest of us are driving EVs?