# [EVDL] Physics



## EVDL List (Jul 27, 2007)

Is it done at the motor/engine's maximum efficiency? Is it done with an 
automatic or manual transmission?


----- Original Message ----- 
From: "storm connors" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, April 06, 2008 1:13 PM
Subject: [EVDL] Physics


> "It takes the same amount of energy to get to 50 mph whether you do it
> in 5 seconds or 40 seconds." This statement appeared on the Volt
> site. It sure doesn't jibe with my experience, but it does seem to be
> supported by the conservation of energy law. The vehicle moving at 50
> mph has a fixed amount of kinetic energy.
>
> Any comment?
>
> -- 
> http://www.austinev.org/evalbum/1059
> http://stormselectric.blogspot.com/
> Storm
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev 

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## EVDL List (Jul 27, 2007)

Efficiency is generally lower at higher acceleration. It's a huge
difference in ICEs, and a moderate difference in EVs. Look at the
torque curve for an ADC motor; if you're operating it at the high end
of its torque curve, it has lower efficiency.

Also, if you travel the same distance at 50mph but spend different
amounts of time accelerating, then when you accelerate more quickly, a
greater portion of the distance is spent at 50mph. Because it takes
more energy (per mile) to travel at higher speeds, total energy
consumption will be higher.

-Morgan LaMoore



> storm connors <[email protected]> wrote:
> > "It takes the same amount of energy to get to 50 mph whether you do it
> > in 5 seconds or 40 seconds." This statement appeared on the Volt
> > site. It sure doesn't jibe with my experience, but it does seem to be
> ...


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## EVDL List (Jul 27, 2007)

So, theoretically it is a true statement, but reality differs. How do
I tell the efficiency from the torque curve? Going up the hill to my
house on low batteries, what should I be doing? I have been keeping
the voltage as high as possible by minimizing the amperage.
Unfortunately, since I am going so slow, I have to do this for a long
time. There must be an optimum approach.



> Morgan LaMoore <[email protected]> wrote:
> > Efficiency is generally lower at higher acceleration. It's a huge
> > difference in ICEs, and a moderate difference in EVs. Look at the
> > torque curve for an ADC motor; if you're operating it at the high end
> ...


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## EVDL List (Jul 27, 2007)

"It takes the same amount of energy to get to 50 mph whether you do it
in 5 seconds or 40 seconds."

True only in textbook physics world, in vacuum with no friction and
ideal efficiencies. Real world physics is a tad bit more complicated
than that.

-kert

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## EVDL List (Jul 27, 2007)

> storm connors wrote:
> 
> > "It takes the same amount of energy to get to 50 mph whether
> > you do it in 5 seconds or 40 seconds." This statement
> ...


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## EVDL List (Jul 27, 2007)

> storm connors wrote:
> 
> > How do I tell the efficiency from the torque curve?
> 
> ...


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## EVDL List (Jul 27, 2007)

> Roger Stockton <[email protected]> wrote:
> > Watch the battery voltage and current, as you try different methods of climbing the hill. The most efficient approach is the one that minimizes the power at the battery.
> >
> > To figure out which approach uses the least energy, compare the products of the power and the time required to climb the hill for each method; the smallest value is the one that uses the least energy overall, even if it is not the approach that operates the motor in the most efficient way.
> ...


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## EVDL List (Jul 27, 2007)

> Morgan LaMoore wrote:
> 
> > I disagree; you're neglecting the efficiency of the battery.
> 
> ...


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## EVDL List (Jul 27, 2007)

The amount of extra energy needed to change the kenetic energy of the
vehicle from 0 to 50 mph is the same either way.

But, if your goal is simply to get to 50 mph, then it uses less total
energy to do it in 5 seconds, because you don't have to spend as much
time/energy at the lower speeds overcoming losses.
However, if your goal is to get from point A to point B then it uses less
total energy to accelerate in 40 seconds because you spend less time on
the trip at the higher velocities. If, for example, your trip is so short
that by the time you spend 40 seconds accelerating to 50 mp, you are at
the halfway point and need to start slowing down, you only spend 1 second
at 50 mph and only have 1 second worth of aerodynamic losses. If you got
to 50 mph in 5 seconds, then you'd spend 20 seconds (or whatever) at 50
mph accumulating 50 mph losses.

At any rate, the statement is true.

> "It takes the same amount of energy to get to 50 mph whether you do it
> in 5 seconds or 40 seconds." This statement appeared on the Volt
> site. It sure doesn't jibe with my experience, but it does seem to be
> supported by the conservation of energy law. The vehicle moving at 50
> mph has a fixed amount of kinetic energy.
>
> Any comment?
>
> --
> http://www.austinev.org/evalbum/1059
> http://stormselectric.blogspot.com/
> Storm
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


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## EVDL List (Jul 27, 2007)

> On 6 Apr 2008 at 13:52, storm connors wrote:
> 
> > Going up the hill to my house
> > on low batteries, what should I be doing? I have been keeping the voltage
> ...


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## EVDL List (Jul 27, 2007)

Hi Storm, an EVerybody;

Ha Ha well CONSIDER the source? General Murders? Sure doesn't jibe with 
the Rest of the Laws of Physics, ether? You SEE it when ya drive your EV, 
right in your face, volt and amp meter. To get the vehicle up to 50 it USED 
X amount of power. No free lunch! Of course you use less power over a given 
time if you take 2 minutes instead of 4 seconds, like White Zoombie does! 
Zombie has top use several hundred HP to do it. A time/energy expanded 
thing? Not a physics major, I barely got through High Skool!Shade tree 
mechanic here! Got the speling to prove it<g>!

Seeya

Bob
----- Original Message ----- 
From: "storm connors" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, April 06, 2008 1:13 PM
Subject: [EVDL] Physics


> "It takes the same amount of energy to get to 50 mph whether you do it
> in 5 seconds or 40 seconds." This statement appeared on the Volt
> site. It sure doesn't jibe with my experience, but it does seem to be
> supported by the conservation of energy law. The vehicle moving at 50
> mph has a fixed amount of kinetic energy.
>
> Any comment?
>
> -- 
> http://www.austinev.org/evalbum/1059
> http://stormselectric.blogspot.com/
> Storm
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev 

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


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## EVDL List (Jul 27, 2007)

> Bob Rice wrote:
> > I barely got through High Skool!Shade tree
> > mechanic here! Got the speling to prove it!
> 
> ...


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## EVDL List (Jul 27, 2007)

I think if White Zombie took 4 seconds zero to 50 it must be
pulling a trailer



> Bob Rice <[email protected]> wrote:
> > Hi Storm, an EVerybody;
> >
> > Ha Ha well CONSIDER the source? General Murders? Sure doesn't jibe with
> ...


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## EVDL List (Jul 27, 2007)

Hello Everybody,

Here is one test you can do if you have road course to do it, to see how 
much energy it takes to drive a EV on a flat grade and on a hill grade for 
exactly one mile for a set amount of time.

Here is my results driving in a residential area for a speed of 15 mph for a 
distance of one mile, with only one stop at the half mile distance:

Driving on flat grade that start out from my house going north for one mile 
loop in 1st gear overall ratio of 19.495:1 at 15 mph at 3500 rpm with a 
GE-11 80 motor amps and 30 battery amps (with the accessory drive units off) 
at full charge battery pack starting voltage of 202 volts, results in 3.6 
ampere hour use for the one mile distance.

Had to charge the 12 volt battery with the onboard 12 volt charger.

Driving on a very steep hill that starts out from my house going south for a 
one mile loop of which 1/2 mile is at or more than 7 percent grade with only 
one stop at the top of this hill, with the accessory drive off in 1st gear 
at 15 mph with a 200 motor ampere and 70 battery ampere with a full charge 
battery pack starting voltage of 202 volts.

Coming back down this hill, the battery voltage starts out at 192 volts at 0 
battery amperes, but this time the motor pilot shaft is engage to power the 
alternator-inverter-converter drives to power fans, heating water pumps, 
electric heating, electric power steering, electric vacuum pump, etc.

While the main motor ampere and main battery ampere was reading 0 amps, but 
my accessory drive was reading about 80 amps at 14.5 volts using MECH.REGEN 
energy while holding my speed down the hill at 15 mph, my total ampere hour 
usage for this hill run was 2.9 ah.

The 12 volt battery is fully charge which indicates 100% SOC at the end of 
this hill test.

How about that! 3.6 AH use on flat grade with accessories off and 2.9 AH 
use on a up and down hill grade with accessories on during the down hill 
grade.

Roland


> > ----- Original Message -----
> > From: "storm connors" <[email protected]>
> > To: "Electric Vehicle Discussion List" <[email protected]>
> > Sent: Sunday, April 06, 2008 1:13 PM
> > Subject: [EVDL] Physics
> >
> >
> >
> >
> > > "It takes the same amount of energy to get to 50 mph whether you do it
> > > in 5 seconds or 40 seconds." This statement appeared on the Volt
> > > site. It sure doesn't jibe with my experience, but it does seem to be
> > > supported by the conservation of energy law. The vehicle moving at 50
> > > mph has a fixed amount of kinetic energy.
> > >
> > > Any comment?
> > >
> > > --
> > > http://www.austinev.org/evalbum/1059
> > > http://stormselectric.blogspot.com/
> > > Storm
> > > 

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## EVDL List (Jul 27, 2007)

Excellent data point Roland. Thanks for the effort to quantify it. You
realize of course, that regen is not worth the effort, however, so you
should immediately re-design your implementation to conform to generally
accepted theory.


Jeff Andre
Chapel Hill, NC



> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of Roland Wiench
> Sent: Monday, April 07, 2008 11:05 AM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Physics
> 
> Hello Everybody,
> 
> Here is one test you can do if you have road course to do it, 
> to see how much energy it takes to drive a EV on a flat grade 
> and on a hill grade for exactly one mile for a set amount of time.
> 
> Here is my results driving in a residential area for a speed 
> of 15 mph for a distance of one mile, with only one stop at 
> the half mile distance:
> 
> Driving on flat grade that start out from my house going 
> north for one mile loop in 1st gear overall ratio of 19.495:1 
> at 15 mph at 3500 rpm with a
> GE-11 80 motor amps and 30 battery amps (with the accessory 
> drive units off) at full charge battery pack starting voltage 
> of 202 volts, results in 3.6 ampere hour use for the one mile 
> distance.
> 
> Had to charge the 12 volt battery with the onboard 12 volt charger.
> 
> Driving on a very steep hill that starts out from my house 
> going south for a one mile loop of which 1/2 mile is at or 
> more than 7 percent grade with only one stop at the top of 
> this hill, with the accessory drive off in 1st gear at 15 mph 
> with a 200 motor ampere and 70 battery ampere with a full 
> charge battery pack starting voltage of 202 volts.
> 
> Coming back down this hill, the battery voltage starts out at 
> 192 volts at 0 battery amperes, but this time the motor pilot 
> shaft is engage to power the alternator-inverter-converter 
> drives to power fans, heating water pumps, electric heating, 
> electric power steering, electric vacuum pump, etc.
> 
> While the main motor ampere and main battery ampere was 
> reading 0 amps, but my accessory drive was reading about 80 
> amps at 14.5 volts using MECH.REGEN energy while holding my 
> speed down the hill at 15 mph, my total ampere hour usage 
> for this hill run was 2.9 ah.
> 
> The 12 volt battery is fully charge which indicates 100% SOC 
> at the end of this hill test.
> 
> How about that! 3.6 AH use on flat grade with accessories 
> off and 2.9 AH use on a up and down hill grade with 
> accessories on during the down hill grade.
> 
> Roland
> 
> 
> > > ----- Original Message -----
> > > From: "storm connors" <[email protected]>
> > > To: "Electric Vehicle Discussion List" <[email protected]>
> > > Sent: Sunday, April 06, 2008 1:13 PM
> > > Subject: [EVDL] Physics
> > >
> > >
> > >
> > >
> > > > "It takes the same amount of energy to get to 50 mph 
> whether you 
> > > > do it
> > > > in 5 seconds or 40 seconds." This statement appeared 
> on the Volt 
> > > > site. It sure doesn't jibe with my experience, but it 
> does seem to 
> > > be > supported by the conservation of energy law. The vehicle 
> > > moving at 50 > mph has a fixed amount of kinetic energy.
> > > >
> > > > Any comment?
> > > >
> > > > --
> > > > http://www.austinev.org/evalbum/1059
> > > > http://stormselectric.blogspot.com/
> > > > Storm
> > > >
> 
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

_______________________________________________
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## EVDL List (Jul 27, 2007)

False for a few real-world reasons:

1. Faster acceleration requires more amps, which generates more heat,
which generates more resistance, which cases efficiency to drop.
2. As someone else has mentioned, batteries voltage will sag a bit
when outputting more amps.
3. #1 and #2 are basically the "Peukert Effect"
4. The most important real-world reason is that the statement only
covers half of the picture: Eventually, in the real-world, you are going to
have to slow down or come to a stop. If you jumped straight to 50mph then
you will have more momentum that you need to negate when you slow down or
stop. Most EVs don't have Regen, and even if you had it, Regen is never a
100% electrical gain of your momentum. You just wasted energy because you
had to unnecessarily slow down when someone cut you off, braked, red light,
fire truck, pedestrian, etc. Had you been going slower then you would not
have had to lose so much momentum, maybe you wouldn't have even had to touch
your brakes. In an EV, especially one w/ Regen, if you have to touch your
brakes then you were going too fast. Obviously it is impossible to not
touch the brakes in the real world: Stop-Signs, 90 degree turns, etc.
However, the statement still holds true: If you have to touch your brakes to
make a 90 degree turn then you were going too fast to take that turn and you
should have been traveling slower. Any time you touch your brakes you lose
valuable potential energy. The more you conserve your momentum the more
efficient you will drive.
NOTE: This general theory probably breaks down at excessively slow
speeds, but I assume no one drives their EV around at <5mph.

Pv

On Sun, Apr 6, 2008 at 10:13 AM, storm connors <[email protected]>


> wrote:
> 
> > "It takes the same amount of energy to get to 50 mph whether you do it
> > in 5 seconds or 40 seconds." This statement appeared on the Volt
> ...


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## EVDL List (Jul 27, 2007)

> Jeff Andre wrote:
> 
> > Excellent data point Roland. Thanks for the effort to
> > quantify it.
> ...


----------



## EVDL List (Jul 27, 2007)

Yes, you missed it.

In each case during the flat and uphill drive, the main battery was powering 
the motor, the accessory drive was not connected to the main motor.

This show a 3.6 - 2.9 = 0.7 ah difference.

The down hill run, the accessory drive was connected to the motor while the 
main battery was at 0 amps.

Now if I had the accessories power off the main battery which I had at one 
time, the EV will run away on this hill and one time, I went sides ways on 
it when it was very icy! The main battery amps was at about 30 amps instead 
of 0 amps I have now.

So this system I have now, is equal to a savings of 30 amps at 180 volts or 
5.4 kw during these down hill runs.

With the accessory drive unit connected to the pilot shaft of the motor by 
way of a clutch, I now can have this EV walk down this hill and at the same 
time generating, 14.5 volts at 60 amps and 120 vAC 60 hz at 20 amps for the 
heater, pumps and fans.

It's a safety item, in this country for me.

Roland


----- Original Message ----- 
From: "Roger Stockton" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Monday, April 07, 2008 7:39 PM
Subject: Re: [EVDL] Physics




> > Jeff Andre wrote:
> >
> > > Excellent data point Roland. Thanks for the effort to
> > > quantify it.
> ...


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## EVDL List (Jul 27, 2007)

> > "It takes the same amount of energy to get to 50 mph whether you do it
> > in 5 seconds or 40 seconds." This statement appeared on the Volt
> > site. It sure doesn't jibe with my experience, but it does seem to be
> > supported by the conservation of energy law. The vehicle moving at 50
> > mph has a fixed amount of kinetic energy.

The statement is technically true. The problem is that the statement
is assuming 100% (or at least fixed) efficiency in the system
providing the energy to the object (car), or that the only energy
considered is the net energy change. The statement doesn't take into
account any energy used to overcome frictional losses whether those be
mechanical friction, chemical friction, electrical friction, or any
other sort of losses. Statements such as what appeared on the Volt
site is a classic example of one made with absolutely no parameters
given. With the correct parameters the statement is true.
Unfortunately, I believe it may have been intended to apply to all
situations as measured at the wall plug/gas pump. Hence the statement
is false.

Nuf said.

-- 
David D. Nelson

http://evalbum.com/1328

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## EVDL List (Jul 27, 2007)

Just for fun, I threw some numbers at it. Let's say constant acceleration for simplicity, and the car takes about 5 kW to overcome rolling resistance at 50 mph, and about 5 kW to overcome air drag at 50 mph.

50 mph = 22 m/s

a1 = 22 m/s / 5 s = 4.4 m/s^2
a2 = 22 m/s / 40 s = 0.55 m/s^2

x1 = a1 * t^2 / 2 = 55 m
x2 = a2 * t^2 / 2 = 440 m

E = energy = Force * distance = Power * time
E1 = 5 kW * 5 s / 2 + 5 kW * 5 s / 3 = 21 kJ
E2 = 5 kW * 40 s / 2 + 5 kW * 40 s / 3 = 167 kJ

So just in the physics sense, it takes alot more energy to go 440 m than 55 m, no surprise.

However, in one case it is accelerating at 8 times the rate of the other, and will take 8 or more times the current to do so, and hence 64 times the I^2*R losses.

So let's say the fast guy is losing 1/2 of his electrical energy to robust acceleration, and the slow guy is losing none (voltage sags to 1/2 value at max power, and little at modest currents). Let's further assume the volt is getting 1/2 its accelerating power from the batteries, and 1/2 from the gas motor. Also, for simplicity assume the same amount of gas is used in both cases (a gas engine is actually more efficient per hp produced the more hp it produces).

E1lost ~ 1500 kg * 4.4 m/s^2 * 55 m / 2 = 182 kJ

E1 = 182 kJ + 21 kJ = 203 kJ
E2 = 167 kJ 

Surprisingly close!

So totally handwavy, back-of-the-envelope, but I could believe the energy is the same for 5 and 40 seconds. If it isn't exactly 5 and 40 seconds, you could find two times that had equal energy used. Remember the slower case drives much more distance.

For the same distance, however, slower (but not crawling) definitely uses less energy!

----- Original Message ----
> "It takes the same amount of energy to get to 50 mph whether you do it
> in 5 seconds or 40 seconds." This statement appeared on the Volt
> site. It sure doesn't jibe with my experience, but it does seem to be
> supported by the conservation of energy law. The vehicle moving at 50
> mph has a fixed amount of kinetic energy.

...The statement is technically true. The problem is that the statement
is assuming 100% (or at least fixed) efficiency in the system
providing the energy to the object (car), or that the only energy
considered is the net energy change. The statement doesn't take into
account any energy used to overcome frictional losses whether those be
mechanical friction, chemical friction, electrical friction, or any
other sort of losses. Statements such as what appeared on the Volt
site is a classic example of one made with absolutely no parameters
given. With the correct parameters the statement is true. ...






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## EVDL List (Jul 27, 2007)

> Roland Wiench wrote:
> 
> > Yes, you missed it.
> 
> ...


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## EVDL List (Jul 27, 2007)

Hello Roger,

In either June or July I will be testing out four IOTA DC-DC converters that 
will be connected in series to power two drive motors that will run the 
accessory units while the main motor is under controller power and 
disconnects from the accessory drive by means of a electric clutch.

This time, when I let up on the accelerator, the converters will go off the 
line and the main motor will connect to the accessory drive, if I choose to 
select this mode of operation with a on console selector switch which will 
be normally set to automatic mode when the streets are snow pack and icy.

This should give me more efficiency during the motor power on mode.

In the winter, this EV is normally pushing through 6 to 12 inches of snow on 
the streets, which the winter time AH usage per mile could be between 4 and 
5 AH as compare to 2.5 to 3.5 in the summer on these rough stone streets.

Roland




----- Original Message ----- 
From: "Roger Stockton" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Tuesday, April 08, 2008 7:06 PM
Subject: Re: [EVDL] Physics




> > Roland Wiench wrote:
> >
> > > Yes, you missed it.
> >
> ...


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## EVDL List (Jul 27, 2007)

> Roger Stockton <[email protected]> wrote:
> If your EV goes sideways using the brakes but not when using the
> accessory load to slow it, this is because your friction brakes are
> locking the front wheels when applied while the accessory load only
> ...


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