Hybrid Car – More Fun with Less Gas

70 mpg - Page 13

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Posted by Neo on January 16, 2010, 9:22 am

Li-ion and Li-FE batteries can only sustain a limited number of full-
before they die. To extend the life of Li-ion and Li-FE(PO4) batteries
a computer
monitor is used to prevent the battery cells from fully discharging
and start to
recharge the battery at an earlier time. The reports I've read seems
to suggest
that the earlier the recharging occurs the longer the battery will
live - but this
means only using a fraction of the available power of the battery
system -
so there is this trade off between the lifespan of the battery and the
range of
the BEV.  Engineering tricks to extend the range with a limited
battery power
includes installing a huge battery pack (BYDs e6), decreasing the
of  the vehicle (Tesla Roadster), making the BEV very light and
(Aptera 2e), having an onboard ICE electric generator(chevy Volt),
the range (Toyota PHEV prius), reducing the lifespan of the battery,
a compromise of all  the above (Nissan Leaf). Other things that
or diminsh the lifespan of the battery (and effect the charge it can
hold) is the operating temperature of the battery when it is under
To maximize the battery power of the Tesla Roadster, Tesla motors uses
a battery anti-freeze/liquid coolant system to prevent the batteries
overheating when under high electric load. Currently the Toyota Prius
and the Honda Insight HEV only air cool their NiCad Battery packs.
The battery has an optimum temperature range - when the temperature
is too high the battery ages prematurely and when the temperature is
low the battery maximum load (SOC) diminishes.

Posted by Michael B on January 16, 2010, 1:27 pm

The Prius charger kicks in when the battery is at 80%.
And it has a CVT, so may not do well with hauling heavier

Posted by Bruce Richmond on January 15, 2010, 3:18 am

Your ideas on the effects of weight on fuel economy need some
revision.  Driving down the highway at near constant speed added
weight has almost no effect on fuel mileage.  It does take more fuel
to accelerate, but much of that energy can be recovered by a hybrid
with regenerative braking.

Recently I purchased two ton of coal from a store near where I work,
11 miles from home.  Rather than pay them to deliver it to my home, or
borrow a truck and make a special trip myself, I just loaded 800 lbs
into my car each day for five days.  That way I figured the only cost
for transport would be the additional fuel used for my trip home as
compared to not having the coal in the car.  The car happen to be a
2001 Prius that has a readout for instantaneous and average fuel
milage.  It also has regenerative braking.  Turned out that I got 52
mpg, about the same as I get without the extra 800 lbs.  The main
difference was that acceleration was sluggish due to the extra
weight.  The trip was mostly on level roads with a few gentle hills.


Before anyone gives me grief about hauling 800 lbs of coal in the car,
just think of it as four two hundred pound passengers :)

The other day I tried keeping the speed down around 40 to 50 mph for a
40 mile trip over secondary roads.  The Prius averaged 60 mpg.  I have
several motorcycles.  The one that gets the best mileage is a 1981 GPZ
550 Kawasaki.  At 55 mph it gets 55 mpg.  This 1972 BMW 750 only gets
about 15 mpg


But somehow that doesn't bother me a bit :)  That's me driving 66.  We
took 3rd in the championship last year.

Posted by Neo on January 15, 2010, 12:55 pm

After 45mph - when driving at a constant speed 50% of all the
energy expended by a motor vehicle is used to overcome wind
resistance.  Your Prius is about 3200lbs so adding 800lbs of
payload is is adding about 25% of extra weight to the Prius
which should be within its designed performance.  I personally
go about 55mpg on a 2006 Prius on a long trip from Washington
DC to Grand Rapids Michigan - my mileage would have
been better if I had not sped up to 70mph in Michigan but
almost all the vehicles on the super highway in Michigan
are going at 70 to 80 mph there. However, while I was in
Maryland, Pennsylvania, and Ohio I drove about 55 mph
(I believe I could have gotten 60mph if I stuck to 55mph
all the way) .

Question:  Does a motorcycle wind cowls help with either
performance or fuel efficiency? If so how much?

Posted by vaughn on January 15, 2010, 10:56 pm

It depends!  A properly designed full faring can certainly reduce air drag and
increase performance.  On the other hand, many years ago I put a handlebar
fairing with a windhield on my 1965 BMW.  It noticably decreased performance,
but I kept it because it increased my comfort and seemed to help the 4-wheel
drivers spot me.


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---> Re: 70 mpg Jim Wilkins01-03-2010
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