The Natural Philosopher gurgled happily, sounding much like they
were saying:

And the answer to how big that is, is well under half a tonne for the
smaller one.

...or about half the weight of the rest of the car...

Similar to the power train on an IC car.

Rubbish. Rover's K-series weighs about 130kg with transmission. Add 50kg
for fuel, and you have a complete powertrain with a 300 mile range (and
five minutes recharge for the next 300 miles) for 40% of that "half a
ton".

The powertrain on a 2cv - engine and gearbox - is light enough to be
carried by two people. With 25 litres of fuel, it'll give a four-seater
car weighing half a ton _complete_ a range of 200+ miles.