On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com"
<bsr3997@my-deja.com> wrote:

>On Oct 10, 1:55 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
>wrote:
>> BobG wrote:
>> > Actually looks pretty slippery. .25KWhr per mile perhaps?
>>
>> In a flat country like Holland maybe ?
>>
>> Graham
>
>I did a google for "road horsepower" and the first link was for a
>Toyota MR2.
>
>http://www.mr2.com/MR2TechData.html
>
>A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>746=10.444 KW, which is what would be needed to cover 50 miles.
>10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>unrealistic and would give .20888/.85 = .246 KWhr/mi. This thing
>looks like it probably has a lower CD than an MR2. BTW that 14.0 hp
>was broken down into
>
>Friction and tire losses @ 50 mph ..... 5.5 hp
>Aerodynamic drag @ 50 mph ............. 8.5 hp
>
>Bruce
>
>
I think you missed something here. According to your figures, it will
take just over 200 watts to move the car at 50 mph for one mile.
That's not the figure given of 14 hp, that's more like 1/4 hp expended
to move one mile. You have to expend that power at a constant rate of
14 hp or 10.444 kW. Look at it another way.

W=ExI

Where W=watt
E=voltage
I=current (in amps)

To make the math easer, assume you have a 100 volt battery. Then
solve for current using:

I=W/E I=10444watts / 100volts I=104.44amps

We have a constant current draw of 104.44 amps required to propel the
car at 50 mph. That is the reason why it is really hard to get an
electric car to have a reasonable range (200 miles) at a reasonable
speed (50 mph). You would be looking at a total power expenditure of
over 41.7 kW to drive for 200 miles at 50 mph. That figure assumes no
head wind and level ground. Add in real life conditions and you might
be looking at power expenditures of around 45 to 50 kW. Also, you'd
flat get run over driving around here on the highway at 50 mph. You'd
better be traveling at least 60 mph which would boost your totals even
more.

Even if you had a battery that could deliver that much power, you
still have the problem of getting all that power back into the
battery. In order to replace 41.7 kW using your 120 vac outlet, you
need to draw over 41 amps for 8 hours. That is assuming 100% recharge
efficiency.

You can draw your own conclusions regarding the practicality electric
cars.

Jack


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Joe wrote:
> Learn more http://Muvy.org
>

If true it won't be allowed in the US. They will find or invent a
problem with it.

 

Joe wrote:
> Learn more http://Muvy.org
>

If true it won't be allowed in the US. They will find or invent a
problem with it.

 

Retired VIP wrote:
> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com" wrote:
>> http://www.mr2.com/MR2TechData.html
>>
>> A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>> 746=10.444 KW, which is what would be needed to cover 50 miles.
>> 10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>> unrealistic and would give .20888/.85 = .246 KWhr/mi.
....
> I think you missed something here. According to your figures, it will
> take just over 200 watts to move the car at 50 mph for one mile.

No, it takes 10.444 kW to move the car at 50 mph.
It takes just over 200 watt-hours to move the car one mile at 50 mph.

> To make the math easer, assume you have a 100 volt battery. Then
> solve for current using:

Why not 300V? 600V? 1000V? Wouldn't higher voltage be easier for the
electronics than lower voltage?

> We have a constant current draw of 104.44 amps required to propel the
> car at 50 mph. That is the reason why it is really hard to get an
> electric car to have a reasonable range (200 miles) at a reasonable
> speed (50 mph). You would be looking at a total power expenditure of
> over 41.7 kW to drive for 200 miles at 50 mph.

It's not the amps, it's the wattage. It's all 10kW no matter how you
slice it. If this was a 1000V system then it would only be 10.4 amps.
10 Amps doesn't sound like a problem.

> Even if you had a battery that could deliver that much power, you
> still have the problem of getting all that power back into the
> battery. In order to replace 41.7 kW using your 120 vac outlet, you
> need to draw over 41 amps for 8 hours. That is assuming 100% recharge
> efficiency.

Those new lithium batteries seem to be able to give 200+ mile range
to electric cars without any problems (except being expensive). I
would imagine you would recharge using a 220V appliance outlet like
they use for electric dryers, electric ovens and air conditioners.
Besides, who drives 200+ miles a day? If you drive only 30 or 40
miles then the battery won't be completely flat and it won't take
as much to recharge.

Anthony

 

Retired VIP wrote:
> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com" wrote:
>> http://www.mr2.com/MR2TechData.html
>>
>> A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>> 746=10.444 KW, which is what would be needed to cover 50 miles.
>> 10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>> unrealistic and would give .20888/.85 = .246 KWhr/mi.
....
> I think you missed something here. According to your figures, it will
> take just over 200 watts to move the car at 50 mph for one mile.

No, it takes 10.444 kW to move the car at 50 mph.
It takes just over 200 watt-hours to move the car one mile at 50 mph.

> To make the math easer, assume you have a 100 volt battery. Then
> solve for current using:

Why not 300V? 600V? 1000V? Wouldn't higher voltage be easier for the
electronics than lower voltage?

> We have a constant current draw of 104.44 amps required to propel the
> car at 50 mph. That is the reason why it is really hard to get an
> electric car to have a reasonable range (200 miles) at a reasonable
> speed (50 mph). You would be looking at a total power expenditure of
> over 41.7 kW to drive for 200 miles at 50 mph.

It's not the amps, it's the wattage. It's all 10kW no matter how you
slice it. If this was a 1000V system then it would only be 10.4 amps.
10 Amps doesn't sound like a problem.

> Even if you had a battery that could deliver that much power, you
> still have the problem of getting all that power back into the
> battery. In order to replace 41.7 kW using your 120 vac outlet, you
> need to draw over 41 amps for 8 hours. That is assuming 100% recharge
> efficiency.

Those new lithium batteries seem to be able to give 200+ mile range
to electric cars without any problems (except being expensive). I
would imagine you would recharge using a 220V appliance outlet like
they use for electric dryers, electric ovens and air conditioners.
Besides, who drives 200+ miles a day? If you drive only 30 or 40
miles then the battery won't be completely flat and it won't take
as much to recharge.

Anthony

 

On Oct 21, 10:09 pm, Retired VIP <Jackj14...@yahoo.com> wrote:
> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3...@my-deja.com"
>
>
>
>
>
> <bsr3...@my-deja.com> wrote:
> >On Oct 10, 1:55 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
> >wrote:
> >> BobG wrote:
> >> > Actually looks pretty slippery. .25KWhr per mile perhaps?
>
> >> In a flat country like Holland maybe ?
>
> >> Graham
>
> >I did a google for "road horsepower" and the first link was for a
> >Toyota MR2.
>
> >http://www.mr2.com/MR2TechData.html
>
> >A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
> >746=10.444 KW, which is what would be needed to cover 50 miles.
> >10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
> >unrealistic and would give .20888/.85 = .246 KWhr/mi. This thing
> >looks like it probably has a lower CD than an MR2. BTW that 14.0 hp
> >was broken down into
>
> >Friction and tire losses @ 50 mph ..... 5.5 hp
> >Aerodynamic drag @ 50 mph ............. 8.5 hp
>
> >Bruce
>
> I think you missed something here. According to your figures, it will
> take just over 200 watts to move the car at 50 mph for one mile.
> That's not the figure given of 14 hp, that's more like 1/4 hp expended
> to move one mile. You have to expend that power at a constant rate of
> 14 hp or 10.444 kW. Look at it another way.

Read it again. That is 200 watt hours. Yes, a 1/4 hp motor should be
able to move the car 1 mile in an hour. And a 1 hp motor could move
it 4 miles in an hour. And a 2 hp motor could move it 8 miles in an
hour. And a 14 hp motor could move it 50 miles in an hour. A watt is
energy per unit of time, same as hp. A watt hour is a unit of energy,
as would be a hp hour. that energy out over a long period of
time and the power is low, but the amount of work that can be done is
the same.

> W=ExI
>
> Where W=watt
> E=voltage
> I=current (in amps)
>
> To make the math easer, assume you have a 100 volt battery. Then
> solve for current using:
>
> I=W/E I=10444watts / 100volts I=104.44amps
>
> We have a constant current draw of 104.44 amps required to propel the
> car at 50 mph. That is the reason why it is really hard to get an
> electric car to have a reasonable range (200 miles) at a reasonable
> speed (50 mph). You would be looking at a total power expenditure of
> over 41.7 kW to drive for 200 miles at 50 mph. That figure assumes no
> head wind and level ground. Add in real life conditions and you might
> be looking at power expenditures of around 45 to 50 kW. Also, you'd
> flat get run over driving around here on the highway at 50 mph. You'd
> better be traveling at least 60 mph which would boost your totals even
> more.

The claim made was 120 miles, not 200, and the car should use less
than the 14 hp to go 50 mph. That was the power required to keep a
Toyota MR2 going 50 mph. Even at 14 hp it would only take
10.444*2.4=25 KW hrs to go 120 miles. It would not be unrealistic to
expect this smaller car with better arodynamics to do 50 mph using 10
hp, which would mean about 18 KW hrs to do 120 miles.

> Even if you had a battery that could deliver that much power, you
> still have the problem of getting all that power back into the
> battery. In order to replace 41.7 kW using your 120 vac outlet, you
> need to draw over 41 amps for 8 hours. That is assuming 100% recharge
> efficiency.

120 volts * 20 amps is 2400 watts. 18 KW hrs / 2400 watts = 7.5 hrs.
They did say to plug it in at night, and that it would be recharged in
a few hours. They were probably stretching things a bit, but not all
that much.

Bruce

> You can draw your own conclusions regarding the practicality electric
> cars.
>
> Jack
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000783-0, 10/21/2007
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> - Show quoted text -

 

On Oct 21, 10:09 pm, Retired VIP <Jackj14...@yahoo.com> wrote:
> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3...@my-deja.com"
>
>
>
>
>
> <bsr3...@my-deja.com> wrote:
> >On Oct 10, 1:55 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
> >wrote:
> >> BobG wrote:
> >> > Actually looks pretty slippery. .25KWhr per mile perhaps?
>
> >> In a flat country like Holland maybe ?
>
> >> Graham
>
> >I did a google for "road horsepower" and the first link was for a
> >Toyota MR2.
>
> >http://www.mr2.com/MR2TechData.html
>
> >A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
> >746=10.444 KW, which is what would be needed to cover 50 miles.
> >10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
> >unrealistic and would give .20888/.85 = .246 KWhr/mi. This thing
> >looks like it probably has a lower CD than an MR2. BTW that 14.0 hp
> >was broken down into
>
> >Friction and tire losses @ 50 mph ..... 5.5 hp
> >Aerodynamic drag @ 50 mph ............. 8.5 hp
>
> >Bruce
>
> I think you missed something here. According to your figures, it will
> take just over 200 watts to move the car at 50 mph for one mile.
> That's not the figure given of 14 hp, that's more like 1/4 hp expended
> to move one mile. You have to expend that power at a constant rate of
> 14 hp or 10.444 kW. Look at it another way.

Read it again. That is 200 watt hours. Yes, a 1/4 hp motor should be
able to move the car 1 mile in an hour. And a 1 hp motor could move
it 4 miles in an hour. And a 2 hp motor could move it 8 miles in an
hour. And a 14 hp motor could move it 50 miles in an hour. A watt is
energy per unit of time, same as hp. A watt hour is a unit of energy,
as would be a hp hour. that energy out over a long period of
time and the power is low, but the amount of work that can be done is
the same.

> W=ExI
>
> Where W=watt
> E=voltage
> I=current (in amps)
>
> To make the math easer, assume you have a 100 volt battery. Then
> solve for current using:
>
> I=W/E I=10444watts / 100volts I=104.44amps
>
> We have a constant current draw of 104.44 amps required to propel the
> car at 50 mph. That is the reason why it is really hard to get an
> electric car to have a reasonable range (200 miles) at a reasonable
> speed (50 mph). You would be looking at a total power expenditure of
> over 41.7 kW to drive for 200 miles at 50 mph. That figure assumes no
> head wind and level ground. Add in real life conditions and you might
> be looking at power expenditures of around 45 to 50 kW. Also, you'd
> flat get run over driving around here on the highway at 50 mph. You'd
> better be traveling at least 60 mph which would boost your totals even
> more.

The claim made was 120 miles, not 200, and the car should use less
than the 14 hp to go 50 mph. That was the power required to keep a
Toyota MR2 going 50 mph. Even at 14 hp it would only take
10.444*2.4=25 KW hrs to go 120 miles. It would not be unrealistic to
expect this smaller car with better arodynamics to do 50 mph using 10
hp, which would mean about 18 KW hrs to do 120 miles.

> Even if you had a battery that could deliver that much power, you
> still have the problem of getting all that power back into the
> battery. In order to replace 41.7 kW using your 120 vac outlet, you
> need to draw over 41 amps for 8 hours. That is assuming 100% recharge
> efficiency.

120 volts * 20 amps is 2400 watts. 18 KW hrs / 2400 watts = 7.5 hrs.
They did say to plug it in at night, and that it would be recharged in
a few hours. They were probably stretching things a bit, but not all
that much.

Bruce

> You can draw your own conclusions regarding the practicality electric
> cars.
>
> Jack
>
> ---
> avast! Antivirus: Outbound message clean.
> Virus Database (VPS): 000783-0, 10/21/2007
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>
> - Show quoted text -

 

18KWhrs at $.12 would cost me about $2.16 in Florida... Thats about
what .75 gal costs this week... 120 miles on .75 gal would be 160 mpg
equivalent.... sounds hi to me... 100mpg equiv I might believe....

 

18KWhrs at $.12 would cost me about $2.16 in Florida... Thats about
what .75 gal costs this week... 120 miles on .75 gal would be 160 mpg
equivalent.... sounds hi to me... 100mpg equiv I might believe....

 

On Sun, 21 Oct 2007 22:16:05 -0700, Anthony Matonak
<anthonym40@nothing.like.socal.rr.com> wrote:

>Retired VIP wrote:
>> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com" wrote:
>>> http://www.mr2.com/MR2TechData.html
>>>
>>> A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>>> 746=10.444 KW, which is what would be needed to cover 50 miles.
>>> 10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>>> unrealistic and would give .20888/.85 = .246 KWhr/mi.
>...
>> I think you missed something here. According to your figures, it will
>> take just over 200 watts to move the car at 50 mph for one mile.
>
>No, it takes 10.444 kW to move the car at 50 mph.
>It takes just over 200 watt-hours to move the car one mile at 50 mph.

How can it take 10.444 kW to move a car at 50 mph but only 200 w/hr to
move a car at 50 mph? Remember that a w/hr is a unit of power for a
period of time. A watt is a unit of power without reference to time.
>
>> To make the math easer, assume you have a 100 volt battery. Then
>> solve for current using:
>
>Why not 300V? 600V? 1000V? Wouldn't higher voltage be easier for the
>electronics than lower voltage?

You could use any battery voltage you wish. I chose 100 volts to make
the math easier to follow. The battery voltage would have no effect
on the power requirement.
>
>> We have a constant current draw of 104.44 amps required to propel the
>> car at 50 mph. That is the reason why it is really hard to get an
>> electric car to have a reasonable range (200 miles) at a reasonable
>> speed (50 mph). You would be looking at a total power expenditure of
>> over 41.7 kW to drive for 200 miles at 50 mph.
>
>It's not the amps, it's the wattage. It's all 10kW no matter how you
>slice it. If this was a 1000V system then it would only be 10.4 amps.
>10 Amps doesn't sound like a problem.

It IS the amps and the voltage and the current and the wattage. They
are all related. Power in watts is voltage time current. Yes, you
could use a 1000 volt battery and it would only require a current draw
of 10.4 amps. The power would be the same.
>
>> Even if you had a battery that could deliver that much power, you
>> still have the problem of getting all that power back into the
>> battery. In order to replace 41.7 kW using your 120 vac outlet, you
>> need to draw over 41 amps for 8 hours. That is assuming 100% recharge
>> efficiency.
>
>Those new lithium batteries seem to be able to give 200+ mile range
>to electric cars without any problems (except being expensive). I
>would imagine you would recharge using a 220V appliance outlet like
>they use for electric dryers, electric ovens and air conditioners.
>Besides, who drives 200+ miles a day? If you drive only 30 or 40
>miles then the battery won't be completely flat and it won't take
>as much to recharge.
>
>Anthony

You still have to put the power used back into the battery regardless
of what voltage you use to power the charger or what type of battery
you use.

What about the poor guy who has to travel 1000 miles in his electric
car. Does he drive 200 miles then stop for 8 hours while the battery
is recharged?

Jack


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On Sun, 21 Oct 2007 22:16:05 -0700, Anthony Matonak
<anthonym40@nothing.like.socal.rr.com> wrote:

>Retired VIP wrote:
>> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com" wrote:
>>> http://www.mr2.com/MR2TechData.html
>>>
>>> A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>>> 746=10.444 KW, which is what would be needed to cover 50 miles.
>>> 10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>>> unrealistic and would give .20888/.85 = .246 KWhr/mi.
>...
>> I think you missed something here. According to your figures, it will
>> take just over 200 watts to move the car at 50 mph for one mile.
>
>No, it takes 10.444 kW to move the car at 50 mph.
>It takes just over 200 watt-hours to move the car one mile at 50 mph.

How can it take 10.444 kW to move a car at 50 mph but only 200 w/hr to
move a car at 50 mph? Remember that a w/hr is a unit of power for a
period of time. A watt is a unit of power without reference to time.
>
>> To make the math easer, assume you have a 100 volt battery. Then
>> solve for current using:
>
>Why not 300V? 600V? 1000V? Wouldn't higher voltage be easier for the
>electronics than lower voltage?

You could use any battery voltage you wish. I chose 100 volts to make
the math easier to follow. The battery voltage would have no effect
on the power requirement.
>
>> We have a constant current draw of 104.44 amps required to propel the
>> car at 50 mph. That is the reason why it is really hard to get an
>> electric car to have a reasonable range (200 miles) at a reasonable
>> speed (50 mph). You would be looking at a total power expenditure of
>> over 41.7 kW to drive for 200 miles at 50 mph.
>
>It's not the amps, it's the wattage. It's all 10kW no matter how you
>slice it. If this was a 1000V system then it would only be 10.4 amps.
>10 Amps doesn't sound like a problem.

It IS the amps and the voltage and the current and the wattage. They
are all related. Power in watts is voltage time current. Yes, you
could use a 1000 volt battery and it would only require a current draw
of 10.4 amps. The power would be the same.
>
>> Even if you had a battery that could deliver that much power, you
>> still have the problem of getting all that power back into the
>> battery. In order to replace 41.7 kW using your 120 vac outlet, you
>> need to draw over 41 amps for 8 hours. That is assuming 100% recharge
>> efficiency.
>
>Those new lithium batteries seem to be able to give 200+ mile range
>to electric cars without any problems (except being expensive). I
>would imagine you would recharge using a 220V appliance outlet like
>they use for electric dryers, electric ovens and air conditioners.
>Besides, who drives 200+ miles a day? If you drive only 30 or 40
>miles then the battery won't be completely flat and it won't take
>as much to recharge.
>
>Anthony

You still have to put the power used back into the battery regardless
of what voltage you use to power the charger or what type of battery
you use.

What about the poor guy who has to travel 1000 miles in his electric
car. Does he drive 200 miles then stop for 8 hours while the battery
is recharged?

Jack


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Virus Database (VPS): 000783-0, 10/21/2007
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avast! - copyright (c) 1988-2007 ALWIL Software.
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On Sun, 21 Oct 2007 22:29:47 -0700, "bsr3997@my-deja.com"
<bsr3997@my-deja.com> wrote:

>On Oct 21, 10:09 pm, Retired VIP <Jackj14...@yahoo.com> wrote:
>> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3...@my-deja.com"
>>
>>
>>
>>
>>
>> <bsr3...@my-deja.com> wrote:
>> >On Oct 10, 1:55 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
>> >wrote:
>> >> BobG wrote:
>> >> > Actually looks pretty slippery. .25KWhr per mile perhaps?
>>
>> >> In a flat country like Holland maybe ?
>>
>> >> Graham
>>
>> >I did a google for "road horsepower" and the first link was for a
>> >Toyota MR2.
>>
>> >http://www.mr2.com/MR2TechData.html
>>
>> >A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>> >746=10.444 KW, which is what would be needed to cover 50 miles.
>> >10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>> >unrealistic and would give .20888/.85 = .246 KWhr/mi. This thing
>> >looks like it probably has a lower CD than an MR2. BTW that 14.0 hp
>> >was broken down into
>>
>> >Friction and tire losses @ 50 mph ..... 5.5 hp
>> >Aerodynamic drag @ 50 mph ............. 8.5 hp
>>
>> >Bruce
>>
>> I think you missed something here. According to your figures, it will
>> take just over 200 watts to move the car at 50 mph for one mile.
>> That's not the figure given of 14 hp, that's more like 1/4 hp expended
>> to move one mile. You have to expend that power at a constant rate of
>> 14 hp or 10.444 kW. Look at it another way.
>
>Read it again. That is 200 watt hours. Yes, a 1/4 hp motor should be
>able to move the car 1 mile in an hour. And a 1 hp motor could move
>it 4 miles in an hour. And a 2 hp motor could move it 8 miles in an
>hour. And a 14 hp motor could move it 50 miles in an hour. A watt is
>energy per unit of time, same as hp. A watt hour is a unit of energy,
>as would be a hp hour. that energy out over a long period of
>time and the power is low, but the amount of work that can be done is
>the same.

So 4 hp would move the car 16 miles in an hour (16 mph). A 8 hp motor
would move the car 32 miles. A 16 hp motor would move the car 64
miles. And it would take a 32 hp motor to move the car 128 mph. Holly
smokes, my car should be able to travel at well over 400 mph using its
120 hp motor. Do you see something wrong with this progression?

A watt is a unit of power without regard to time. A wHr is a unit of
work. 10 watts isn't the same as 100 watts but 10 watts applied to a
device for 10 hours will do the same amount of work as 100 watts
applied for 1 hour. The same is true of horsepower, it's a
measurement of power not work. A hpHr is a measurement of work.

So, if it takes 14 hp to move a car at 50 mph without regard to time.
It will take 14 hp to move that car at 50 mph for one minute or one
hour. The only difference is the amount of work done, not the amount
of power needed.

So, his figure of 200 watts to move a car at 50 mph is wrong.

Jack


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On Sun, 21 Oct 2007 22:29:47 -0700, "bsr3997@my-deja.com"
<bsr3997@my-deja.com> wrote:

>On Oct 21, 10:09 pm, Retired VIP <Jackj14...@yahoo.com> wrote:
>> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3...@my-deja.com"
>>
>>
>>
>>
>>
>> <bsr3...@my-deja.com> wrote:
>> >On Oct 10, 1:55 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
>> >wrote:
>> >> BobG wrote:
>> >> > Actually looks pretty slippery. .25KWhr per mile perhaps?
>>
>> >> In a flat country like Holland maybe ?
>>
>> >> Graham
>>
>> >I did a google for "road horsepower" and the first link was for a
>> >Toyota MR2.
>>
>> >http://www.mr2.com/MR2TechData.html
>>
>> >A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>> >746=10.444 KW, which is what would be needed to cover 50 miles.
>> >10.444/50 = .20888 KW hr/mi. An efficiency of 85% would not be
>> >unrealistic and would give .20888/.85 = .246 KWhr/mi. This thing
>> >looks like it probably has a lower CD than an MR2. BTW that 14.0 hp
>> >was broken down into
>>
>> >Friction and tire losses @ 50 mph ..... 5.5 hp
>> >Aerodynamic drag @ 50 mph ............. 8.5 hp
>>
>> >Bruce
>>
>> I think you missed something here. According to your figures, it will
>> take just over 200 watts to move the car at 50 mph for one mile.
>> That's not the figure given of 14 hp, that's more like 1/4 hp expended
>> to move one mile. You have to expend that power at a constant rate of
>> 14 hp or 10.444 kW. Look at it another way.
>
>Read it again. That is 200 watt hours. Yes, a 1/4 hp motor should be
>able to move the car 1 mile in an hour. And a 1 hp motor could move
>it 4 miles in an hour. And a 2 hp motor could move it 8 miles in an
>hour. And a 14 hp motor could move it 50 miles in an hour. A watt is
>energy per unit of time, same as hp. A watt hour is a unit of energy,
>as would be a hp hour. that energy out over a long period of
>time and the power is low, but the amount of work that can be done is
>the same.

So 4 hp would move the car 16 miles in an hour (16 mph). A 8 hp motor
would move the car 32 miles. A 16 hp motor would move the car 64
miles. And it would take a 32 hp motor to move the car 128 mph. Holly
smokes, my car should be able to travel at well over 400 mph using its
120 hp motor. Do you see something wrong with this progression?

A watt is a unit of power without regard to time. A wHr is a unit of
work. 10 watts isn't the same as 100 watts but 10 watts applied to a
device for 10 hours will do the same amount of work as 100 watts
applied for 1 hour. The same is true of horsepower, it's a
measurement of power not work. A hpHr is a measurement of work.

So, if it takes 14 hp to move a car at 50 mph without regard to time.
It will take 14 hp to move that car at 50 mph for one minute or one
hour. The only difference is the amount of work done, not the amount
of power needed.

So, his figure of 200 watts to move a car at 50 mph is wrong.

Jack


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Retired VIP wrote:
> On Sun, 21 Oct 2007 22:16:05 -0700, Anthony Matonak wrote:
>> Retired VIP wrote:
>>> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com" wrote:
>>>> http://www.mr2.com/MR2TechData.html
>>>>
>>>> A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>>>> 746=10.444 KW, which is what would be needed to cover 50 miles.
>>>> 10.444/50 = .20888 KW hr/mi.
>> ...
>>> I think you missed something here. According to your figures, it will
>>> take just over 200 watts to move the car at 50 mph for one mile.
>> No, it takes 10.444 kW to move the car at 50 mph.
>> It takes just over 200 watt-hours to move the car one mile at 50 mph.
>
> How can it take 10.444 kW to move a car at 50 mph but only 200 w/hr to
> move a car at 50 mph? Remember that a w/hr is a unit of power for a
> period of time. A watt is a unit of power without reference to time.

Would you prefer if we said that it takes 10.444 kWh to move a car
50 miles in one hour? How about that it takes 1/50th of that to move
the car just 1/50th of that distance in 1/50th of that time?

I'll let you do the math. Hint. 1/50th of 50 miles is 1 mile.
(I'll let someone else describe w/hr and Whr differences.)

>> Those new lithium batteries seem to be able to give 200+ mile range
>> to electric cars without any problems (except being expensive). I
>> would imagine you would recharge using a 220V appliance outlet.
>
> You still have to put the power used back into the battery regardless
> of what voltage you use to power the charger or what type of battery
> you use.

The wiring in most houses is limited in amperage. Say your car can
only draw 30A from the outlet. If the outlet is 220V then it can get
twice the power than it could if it was 120V. A car that would need
8 hours to recharge on 120V would only need 4 hours on 220V.

Your complaint seems to be that it would take too long to recharge a
car at 120V. I suggest that it wouldn't take too long at 220V.

> What about the poor guy who has to travel 1000 miles in his electric
> car. Does he drive 200 miles then stop for 8 hours while the battery
> is recharged?

What about the poor guy who has to travel 4000 miles? What does he
do for speeding tickets and sleep?

Around these parts, it would take over 18 hours to drive 1000 miles
and anyone who has to drive more than a 1000 miles a day has got bigger
problems than where to plug in his car.

Assuming your car gets some 5 miles/kWh and you get to recharge using a
typical 220V 30A outlet. It would only require 6 hours of recharging for
every 200 miles of driving (more or less). This sounds reasonable to me.

Some folks have been suggesting the use of 'quick charge' outlets that
provide higher voltage, current or both. These could recharge the car
while eating lunch (or dinner).

Anthony

 

Retired VIP wrote:
> On Sun, 21 Oct 2007 22:16:05 -0700, Anthony Matonak wrote:
>> Retired VIP wrote:
>>> On Sun, 21 Oct 2007 17:09:56 -0700, "bsr3997@my-deja.com" wrote:
>>>> http://www.mr2.com/MR2TechData.html
>>>>
>>>> A test by Car & Driver put it at 14.0 hp @ 50 mph. That would be 14*.
>>>> 746=10.444 KW, which is what would be needed to cover 50 miles.
>>>> 10.444/50 = .20888 KW hr/mi.
>> ...
>>> I think you missed something here. According to your figures, it will
>>> take just over 200 watts to move the car at 50 mph for one mile.
>> No, it takes 10.444 kW to move the car at 50 mph.
>> It takes just over 200 watt-hours to move the car one mile at 50 mph.
>
> How can it take 10.444 kW to move a car at 50 mph but only 200 w/hr to
> move a car at 50 mph? Remember that a w/hr is a unit of power for a
> period of time. A watt is a unit of power without reference to time.

Would you prefer if we said that it takes 10.444 kWh to move a car
50 miles in one hour? How about that it takes 1/50th of that to move
the car just 1/50th of that distance in 1/50th of that time?

I'll let you do the math. Hint. 1/50th of 50 miles is 1 mile.
(I'll let someone else describe w/hr and Whr differences.)

>> Those new lithium batteries seem to be able to give 200+ mile range
>> to electric cars without any problems (except being expensive). I
>> would imagine you would recharge using a 220V appliance outlet.
>
> You still have to put the power used back into the battery regardless
> of what voltage you use to power the charger or what type of battery
> you use.

The wiring in most houses is limited in amperage. Say your car can
only draw 30A from the outlet. If the outlet is 220V then it can get
twice the power than it could if it was 120V. A car that would need
8 hours to recharge on 120V would only need 4 hours on 220V.

Your complaint seems to be that it would take too long to recharge a
car at 120V. I suggest that it wouldn't take too long at 220V.

> What about the poor guy who has to travel 1000 miles in his electric
> car. Does he drive 200 miles then stop for 8 hours while the battery
> is recharged?

What about the poor guy who has to travel 4000 miles? What does he
do for speeding tickets and sleep?

Around these parts, it would take over 18 hours to drive 1000 miles
and anyone who has to drive more than a 1000 miles a day has got bigger
problems than where to plug in his car.

Assuming your car gets some 5 miles/kWh and you get to recharge using a
typical 220V 30A outlet. It would only require 6 hours of recharging for
every 200 miles of driving (more or less). This sounds reasonable to me.

Some folks have been suggesting the use of 'quick charge' outlets that
provide higher voltage, current or both. These could recharge the car
while eating lunch (or dinner).

Anthony