Re: The Electric Car

On Thu, 02 Aug 2007 16:52:15 +0100, Eeyore wrote:

On the highway, the engine gets connected directly to the wheels.
This takes the sosses of the electric machines out of the picture.

What losses ? Electric motors are highly efficient.

Any motor inefficiencies are doubled (the generator likely has similar
losses to the motor), and added to any losses in the power electronics
(which may increase when running at full power continuously; e.g.
a MOSFET's R[DS(on)] increases with temperature).

It seems to just argued against using any electric motors at all.

Not at all. Motors are a lot more efficient than an ICE. But if you're
using an ICE as the power source, you're not comparing motor efficiency
against ICE efficiency, but an electric generator->conversion->motor
drivetrain against a mechanical drivetrain.

It may still win, either in absolute or relative terms (i.e. whether or
not you take into account the ability to run the ICE at optimum
speed/load). But for now, the issue is whether it wins by enough to
overcome the inertia of sticking with the "safe" option.

It also allows the engine and both motors to be used for passing power.

At the cost and complexity of requiring a transmission. I just don't see any sense in it.

Mechanical transmission is what they're familiar with. Current hybrids
largely try to tweak existing technology rather than starting with a
clean slate.

Which is why the advantage they offer is so poor.

Do wake up.

You seem to be looking at it from an "ideal world" perspective, i.e.
considering the technology on its merits alone.

I don't think that's a particularly meaningful perspective. None of the
major car makers are going to abandon ICE technology soon, so they will be
looking to "dual-purpose" as much of their existing technology and
infrastructure as possible.

If you design an engine purely for a serial hybrid, the result isn't going
to look anything like a normal car engine. The same applies to much of the
rest of the car: wheels designed for embedded motors won't look like those
designed for an axle. Cooling for an engine whose power doesn't vary with
speed is a different problem than for one which relies upon forward
motion for the airflow. And so on.

A ground-up redesign involves a lot of cost and a lot of risk. Even if
it's successful, you end up competing with yourself, as gains in one
technology don't easily transfer to the other.

I just don't see any major car maker betting their future on electric
vehicles right now. Development will be incremental, and entirely
subordinate to the constraints of their conventional production lines.

.

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