Comment by sam1714
14 hours ago
The Chevy Volt (and it's predecessor the GM 2-mode hybrid, and the Allison power-split hybrid) was a work of art. It is fundamentally a planetary gearbox, with 2 motor-generators.
In ICE mode, under 35 MPH, it worked as a series hybrid. Above 35, the engine mechanically connected to the wheels. One motor-gen extracted power and fed it to the other, acting as a CVT in parallel. This provided the ratio changes needed for the small engine.
It was way too complicated and expensive the two times they tried it (2008, then the Volt). It was successful and lives on to this day in its original application: city buses.
Planetary gear plus 2 motor-generators is 'Toyota Synergy Drive' and also used by Ford and Stellantis in some hybrid models. At least the Ford C-Max and Chrysler Pacifica hybrids use this style drive train. I'm not on top of all the hybrids, but I'd guess if 4 car makers do it, there's others to be found.
It makes a lot of sense, works well, and is very durable... as long as Ford didn't forget to heat treat a bearing or whatever they messed up in early C-Maxes.
I had a 2012 Chevy Volt. It was indeed a delightful car!
But I believe that the series mode was a mistake. The later versions of Volts removed it entirely, improving the fuel economy.
> It was way too complicated and expensive the two times they tried it (2008, then the Volt). It was successful and lives on to this day in its original application: city buses.
I don't think that it was too complicated. Hybrids are using essentially the same system, except that they have a smaller battery and less powerful electric motors.