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Comment by js4all | Hacker News Reader

Tesla is the most innovative brand in cars. We need EVs to get independent from oil.

We are now in a time of pioneers in a new world. There will be a lot of failures but also successes. I have a good feeling with Tesla's way.

Here is why:

    1. The design is exceptional
    2. Their power train is simple. They didn't make the decision to use an extender like Volt which requires three hydraulic clutches
    3. They extend the range through super chargers
    4. They are aiming at the right target group
    5. The time is right
    6. Mr. Musk is a visionary

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> 2. Their power train is simple. They didn't make the decision to use an extender like Volt which requires three hydraulic clutches

A Volt-like extender requires ZERO clutches. It requires nothing more than a gas engine driving a generator which charges a battery which powers an electric motor.

The reason why the Volt has three clutches is straightforward: unlike Tesla, GM is trying to squeeze all the efficiency it can out of the car by taking advantage of the fact that the car actually has three motors in it. The Volt runs in four different modes:

0. The battery-powered traction motor drives the car (the default).

1. The gas engine drives a generator which, with battery support, powers the traction motor to drive the car.

2. The generator disengages from the (turned off) gas engine and performs double-duty as a second battery-driven motor.

3. The gas engine attaches directly to the drivetrain and helps the traction motor drive the car.

Each of these is maximally efficient in different situations. For example, if the battery is nearly depleted and the traction motor is spinning fast (over 70MPH), a gas engine directly assisting the wheels is more efficient than generating electricity for the traction motor.

Here's the dirty secret of the Model S which no one seems to have touched on: despite Tesla's aerodynamic puffery, it's a fairly inefficient electric vehicle. The EPA rates it at just 89MPGe with its lightest battery, compared to (for example) 98MPGe for the Volt, 99 for the Leaf, and 100 for the C-Max Energi. The Model S doesn't really need to maximize efficiency because its battery is big enough to handle range anxiety. But people who really cared about oil independence (as it sounded like you did) would pick the Volt over the Model S.

MPG by itself is not enough to define if a car is "efficient" or not. We'd need more data to determine that.

Isn't the leaf a much smaller car?

Not to mention the fact that any electric car will be more energy efficient than one using an internal combustion engine.

Bah, MPGe, not MPG. And anyway, MPG has been the standard of efficiency measurement for a century now, so such an argument is a bit weaselly, don't you think?

My claim still stands. The Volt doesn't need three clutches, but it has three because GM is concerned about efficiency, and Tesla not as much.

> Not to mention the fact that any electric car will be more energy efficient than one using an internal combustion engine.

The Volt has an ICE.

MPG(e) measures one aspect of efficiency: how much stored energy it takes to move the vehicle a given distance. If you use MPG, then a bus loses big time since a bus gets way lower MPG than a car.

Another measure is per-passenger MPG(e) A bus now looks a whole lot better, and a full Model S with jump-seats is more efficient than a full leaf in terms of per-passenger MPGe.

Another measure of efficiency is how efficient it turns the energy stored (gas, electricity, etc.) into kinetic energy. In this measure the weight of vehicle is irrelevant. The bus probably does pretty well as large diesel engines are typically more efficient than small gas engines, but pretty much all electrics will beat out all ICEs since the best ICE vehicles are a shade under 50% efficient, which is trivially beatable in an electric.

> Another measure is per-passenger MPG(e) A bus now looks a whole lot better, and a full Model S with jump-seats is more efficient than a full leaf in terms of per-passenger MPGe.

All very true, but still very weaselly IMHO. Since the Leaf hauls five passengers, what you're really saying is that the Model S is acceptably efficient only if you're always carrying six passengers. I'm willing to bet that, assuming your Model S even has the child jump-seats in the back, this is probably well less than 10% of the use cases for the kinds of people buying this car.

And of course it's true that an ICE is less efficient than an electric motor. That's not what was claimed. What was claimed was that "any electric car will be more energy efficient than one using an internal combustion engine", that is, dismissing the Volt and C-Max.

I'm not saying that Tesla shouldn't have done what they did: they were very smart in developing a competitor to the BMW 7-series. The long range is smart, and the lack of an ICE backup is smart, and the high-end market is smart. It was the right decision to make. But it is nonetheless still fair to say that the Model S isn't a particularly efficient car in comparison to its electric and plug-in hybrid competition.

The main point was the Model S could easily be just as thermodynamically efficient as the Leaf.

On a side note, I can't fit my family of 5 in a Leaf since kids have to be in a car-seat until age 8, and fitting 3 car-seats in the backseat of a Leaf is a no-go.

Keep in mind that it's a 10-12% difference in mpg. It's like saying the 30mpg car is "inefficient" compared to the 33mpg one.

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