> Although I’m prepared to accept that the Prius is a good compromise (and
> your previous posts have tempted me to look for a used model), your
> assertion sounds like a recipe for perpetual motion. A heavier vehicle
> driven in the same fashion as a lighter one will always use more energy.
No, not at all. I'm not talking about perpetual motion. However, when
you factor in a direct apples-to-apples weight comparison, the
hybrids, like the Prius, are only about a net 100 pounds heavier.
That 100 pounds of extra weight is used to advantage, though. It helps
lower the center of gravity of the vehicle and also attain a better
front-rear weight balance too. All factors which can improve the
handling and ride of the vehicle. The weight disadvantage of the
ancient cell technology used in the Prius is offset by the fact that
there are less cells used and a narrower usage band of stored power to
use. Most Prius models don't try to use electricity as the primary
mode of propulsion, it is used to level out the peaks and valleys and
allow for a highly effecient gas motor that has zilch torque. The
Prius is unique in that it uses two electric motors which dynamically
also function as generators and the gas motor in a super-crazy
four-shaft gear matrix (drive shaft being the fourth) that is the
ultimate in elastic push-pull energy elasticity. Dead Prius batteries
aren't very common at all, and are usually influenced by people trying
to drive them as electric cars, not as hybrids. The best thing you can
do with a Prius is completely forget that you are driving a hybrid.
It's smarter than you, when it comes to energy management.
What's unusual about this matrix is that when you are going up a hill,
the gas motor is running and is usually running at a high power level
which is directly contributing to the propulsion of the vehicle, as
well as is powering the generator which is charging up the batteries
AND is producing surplus electricity which is going to the other
electric motor which is providing torque for acceleration.
When we are talking about vehicles in the 3000 pound range, a
difference of 100 pounds really isn't all that significant. When you
have winds, especially cross-winds, the extra weight actually is an
MPG advantage because there is more resistance to the side load on the
vehicle and less drag-inducing steering into the wind.
The proof in the weight argument is the difference in gas mileage
between a driver-only and four-person trip. When all four of us go
someplace, it's about another 500 pounds in the vehicle. Suprisingly,
the gas mileage is almost identical. At most, we see a 1 MPG drop. So,
500 pounds is a 2% change in gas mileage. This has been consistent
over the five years we've had this car. Air temperature is the biggest
factor in gas mileage. The peak is at about 70 degrees (F). At 0
degrees (F), it's about 20% less gas mileage. At 90 degrees (F), it's
about 5% less gas mileage.
Would we buy another Prius? Highly likely. But BMW has a really nice
hybrid system that we like too. We'll either go Toyota or BMW. Nobody
else has a hybrid system that makes as much sense. Honda is on at
least their fourth version of it and it's still a lose-lose in the
long-run. The only ones I'd own past 100,000 miles is Toyota and BMW.
If I had my druthers, we'd go BMW just because of the legroom and
comfort.
As to non-hybrid vehicles? Fortunately, great strides have been made
in the past five years and you can now get big vehicles that get
excellent gas mileage. The Diesel X5 is one such vehicle. I wouldn't
mind going that route instead of hybrid, but it does depend on your
driving conditions. Driving in hilly or city conditions? The hybrid is
advanteagous. But long-miles on flat highways? Not so much. You only
need about 15 hp to keep a vehicle going down a flat highway,
regardless of weight. All you are doing is maintaining momentum and
overcoming drag. A Deisel motor is extremely good at that.
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
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