[1Old Pro]

the combustion engine doesn’t drive the wheels but instead serves solely as a generator to recharge the battery on the go. This setup allows the engine to run at optimal speeds for maximum efficiency. Examples include the BMW i3 REX, the Ramcharger, Mazda MX-30, Scout’s upcoming truck and SUV, and Nissan’s models equipped with E-Power tech.

So it's for EV's.

[TexasGator]

Yes.

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BMW i3 REX

About 100 mile range on battery.

1.7 gallon gas tank.

[cymbeline]

“allows the engine to run at optimal speeds for maximum efficiency”

I think diesel electric locomotives, which have no batteries, have the ability to configure the windings in the generator so that at low speeds, lower voltage, higher amperage current is delivered to the traction motors.

At high speeds, where the traction motors produce a higher back-voltage, the generators need to feed them a higher voltage.

And keeping the diesel motors running in a decent efficiency range.

Basically, it’s electrical gear shifting.