06 July 2010

Higher efficiency means more variation in range

It became very clear over the course of over 27 thousand miles in the Mini E that the range is very elastic. If I knew I had to go farther than usual, I was confident I could always do it just by driving slower and more gently than usual. As long as the whole trip was less than 150 miles.

The big point here is that the more efficient a drive train is, the more variation in range there will be between driving aggressively and driving gently.

Here is an easy way to think about it without much math:

Let's say you have a very inefficient drive train that wastes 90% of your fuel no matter how you drive. The greatest effect you could have on your range by driving either very aggressively or very gently might be about 10%.

Now let's say you have a very efficient drive train that only wastes 10% of your fuel, worst case. Then you might expect that you could change your range by 90% depending on how you drive.

The average gas car is not as bad as the first example, but not far off.

The Mini E is not quite as good as the second example, but not far off.

Which is why an electric car can have a large variation in range depending on how smart or dumb the driver is about driving on any given day.

And this is also another reason why smart people with a little experience never ever have range anxiety in an electric car. We always start off in the morning with 100% charge, we know what our cars can do and how to get them to do it. And we plan accordingly.

And if we know we have the range, the Mini E has the performance to make dumb driving (that is, fast driving) a really fun time. But only when we know we can afford it. And then there are drivers who just cannot slow down, no matter what. Well, they are another story.

Maybe I'll cook up a first order mathematical treatment of this assertion about range variation if I can get one or two of my engineering buddies to check my work, and I'll post it in the near future.

By the way, show me a car that always has a full tank in the morning, where the driver never has to go out of the way to get fuel, and the driver never has to waste any time while the car is fueling, and I will show you an electric car.

Why is it that carcinogenic car drivers don't get this?

Even though the Mini E was returned a month ago, I plan a few more posts. One will be the experiences of a friend who drove my Mini E for the last few weeks after I moved out of New Jersey. (He liked it, even though he mostly charged it at 12 amps.) Another will be about the amazing "Variac" and why it became my best friend while charging the car at work. Perhaps the last post will be about the problems some people have reported when trying to charge from a generator and how to work around these problems.

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