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Comment by artimaeis | Hacker News Reader

The Chevy Volt and BMW i3 are identical in the regard of the function of their petrol engine. The Volt is using Chevy's Voltec drivetrain, so there's no way for the engine to put power to the wheels except through charging the battery - the same as the i3.

https://en.wikipedia.org/wiki/Chevrolet_Volt

https://en.wikipedia.org/wiki/GM_Voltec_powertrain

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"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."

Yeah not sure how I skipped that part so effectively. I've since looked through what else I can find about that Voltec drivetrain and it's clear that the planetary gear can engage in such a way that the petrol motor can provide assistance to the electric motor.

In case anyone's interested, here's a fairly good and simple explanation of the 3-clutch system which allows the petrol motor to provide some power to the wheels when in the correct scenario: http://www.youtube.com/watch?v=80E1fOp95rA

Yes, this was the explanation I saw when my Girlfriend purchased a used volt last summer. We explain it to most people that the gas engine is there to act as a generator and charge the battery and act as a generator. Not to directly power the car. She loves her car.

This is not correct, also from the Wikipedia link above, describing the Volt driving modes: "Dual motor extended – The electric motors are used again in dual configuration with increased efficiency at higher speeds. Additionally the gasoline engine contributes propulsion power via the planetary gear. While power is drained from the battery the amount is less than in mode 2 for the same propulsion power, thus extending the range."

Emphasis my own.

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