Quote:
Originally Posted by ngcles
Hi Ron,
I applaud this advance and it is good news as a way forward.
One other problem (so far as those living in rural areas is concerned) that also has to be addressed is the fact that the range of electric vehicles is far more limited in highway driving and high-speed cruising, than it is in "city-cycle".
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Hi Les,
At least in the case of the Tesla's, that has not been true since their
introduction, with highway range at 100km/h being slightly greater
than driving a mixed cycle of slow, medium and high speeds.
For example, see :-
https://www.tesla.com/en_AU/blog/dri...model-s-family
Quote:
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Originally Posted by ngcles
Because of the lack of gearing in electric vehicles, they are at their most inefficient when run at high speed almost constantly with few or no brake applications.
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From an engineering perspective, that is also incorrect.
In fact they are at their most efficient.
Internal combustion engine cars have non-linear power bands.
The amount of torque they can deliver is a function of how
many RPM the motor is spinning at.
There is typically an optimal point where they are rotating at a
specific number of RPM in order to produce the maximum torque.
By comparison, the type of AC motors used in a Tesla have
near constant maximum torque from 0 to about 6000 RPM, while
maximum power occurs at about 10000 RPM long before torque
drops off.
So internal combustion engines are at a distinct disadvantage. They
have to have multi-gear transmissions in order to help flatten out their
power curves.
The transmissions are of course bulky, heavy and expensive and so
it is an advantage if the power plant does not require them.
We engineers would probably refer to gear boxes as a bit of a kludge.
They are a cumbersome attempt to overcome the non-linear power-band
characteristics of the power unit.
Speeding up and slowing down sees energy losses in both internal
combustion engine and electric cars but any car with energy recovery
such as regenerative braking has a range advantage.
If anything, in the case of the Telsa's, given the mixed driving cycle
ranges versus the highway ranges are nearly equal, it probably highlights
more the inefficiencies of internal combustion engine vehicles without
regenerative braking in city cycles.
What is true in all vehicles is that aerodynamic drag goes up with
the square of speed. We all know that from driving long distances that
easing off the accelerator a little can increase the range noticeably.
It also says that anything that can be done to reduce aerodynamic drag
is good.
Without the need for the same levels of cooling that internal combustion
engines require, automotive engineers have the potential to design
vehicles with more streamlined profiles as opposed to the house bricks
most of us drive around in today.
