One thing that always puzzled me was how the gas engines in hybrids were so efficient. Technology Connections has a great video explainer: <a href="https://www.youtube.com/watch?v=KnUFH5GX_fI" rel="nofollow">https://www.youtube.com/watch?v=KnUFH5GX_fI
tl;dw: constant RPM and a weird stroke geometry where the power stroke is longer than the other strokes to extract more energy from the expanding gasses.
I'm surprised there isn't more effort to create hybrids in reverse--an electric car with optional gas generator. The gas generator could run at constant speed, never changing RMP, while the battery handles constant changes in acceleration. The idea is not mine. I've heard about it in China
There were several of them: the first and second generations of Chevy Volt, Fisker Karma, BMW i3, and a couple of Chinese brands.
They're less efficient than parallel hybrids at high speeds (on a freeway). And you also need a fairly sizeable engine to keep up with the consumption at freeway speed, so at this point you might as well just throw in a planetary gearbox.
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.
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.
gcanyon · · focus · HN ↗
tl;dw: constant RPM and a weird stroke geometry where the power stroke is longer than the other strokes to extract more energy from the expanding gasses.
jostmey · · focus · HN ↗
cyberax · · focus · HN ↗
They're less efficient than parallel hybrids at high speeds (on a freeway). And you also need a fairly sizeable engine to keep up with the consumption at freeway speed, so at this point you might as well just throw in a planetary gearbox.
sam1714 · · focus · HN ↗
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.
cyberax · · focus · HN ↗
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.