# [EVDL] A less complex Chevy Volt?



## EVDL List (Jul 27, 2007)

72 hp improves reliability -- you can drive the car on just the gas engine =
even if the battery is completely flat or has malfunctioned. Just 25 hp wou=
ld be dangerous in a car this heavy.

More gasoline hp costs little extra, but greatly drives down the cost of th=
e battery pack.

Fixed RPM means a much more sophisticated tranny is needed if the electric =
system breaks.

Not trying to be all negative here -- your ideas are great for what would b=
e small compromises for most drivers, to give up some reliability and the a=
bility to drive up I-70 into Denver at high speed.



________________________________
From: Larry Gales <[email protected]>
To: SEVA <[email protected]>; Electric Vehicle Discussion List <[email protected]=
sjsu.edu>
Sent: Tuesday, August 23, 2011 12:46 AM
Subject: [EVDL] A less complex Chevy Volt?

Using the following equations:
Rolling Resistance RR =3D rrc * weight
Drag =
=3D (0.5) * (rho) * (v**2) * Cd * A
HP =
=3D ( Drag + RR) * V)/550

I compute that a car like the Chevy Volt needs only about 20 HP to cruise at
65 MPH on aflat road with no wind. Yet I understand that the Volt actual=
ly uses a 72
HP gasoline engine: almost 3 times as large. It appears to me that Chevy tr=
ied to do 2 things:

o Produce a series hybrid car with absolutely NO compromises compar=
ed
with a gas engine car:
it can cruise for hundreds of miles at a sustained 100 MPH -- w=
ay
beyond what is needed.

o Create a drive train that achieves the maximum possible efficienc=
y.

This combination of objectives can only be met with a very complex and
expensive setup. I havelooked at aspects of the Volt drive train and it =
seems WAY more complex than
a typical electric car.

So I wonder if the following approaches would be workable:
o A pure series hybrid where you have a fixed RPM gas engine of about =
25
HP which turns on
when the battery gets below a certain amount (it can also be turne=
d on
by the driver at will)
and which simply feeds juice to the battery equivalent to the drai=
n on
the battery when it
is traveling at 65 MPH. If the car is traveling faster, or up h=
ill,
etc, the battery level
will start to drop, but when the the car travels slower, downhill,=
etc,
the battery level
will start to rise again.

I realize that there is about a 20% loss with energy going in and =
out
of the battery, but
if the current Volt gets 40 MPG on its gas engine, this approach s=
hould
get 30-32 MPG
for a very much less complex and expensive system. There would =
also be
some occasions,
such as VERY long hills (e.g., mountain driving), or persistent
headwinds, where the car
could not continue at 65 MPH but would have to slow down to 50-=
60 MPH
or less, but these occasions
should be comparatively rare, but in any case the car would have
unlimited range (within its
gasoline fuel supply).


o Another series concept is whereby a fixed RPM engine sends electrici=
ty
to BOTH the electric motor
and the battery: if the car needs more HP, it adds battery powe=
r to
the electricity coming from the
engine, but if it needs less HP, more of the engine produced
electricity is sent to the battery.
This appears to be more efficient, but also more complex then the
design above, but if the added
complexity is electronic, rather than mechanical, it might not be =
too
bad. I believe that the
current Chevy volt does something like this but than adds the
mechanical complexity of a direct
mechanical connection between the gas engine and the actual wheels.

So a much simpler and less expensive setup should produce a car whose peak
performance is the
same, and whose sustained performance is adequate for the great majority of
time.

I would appreciate any feedback on these concepts.
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## EVDL List (Jul 27, 2007)

I don't see the difference between the two options,
connecting the genset to the battery only (series mode)
and having a full electric drivetrain will automatically
*only* send the difference between elecitric production and
consumption into/out of the pack, the currents from
generator and electric motor balance (cancel out) for the
most part.
The second solution says that the generator will send part
of the energy to the motor and part to the battery, but that
is exactly what automatically will happen when connecting
a generator and a motor to a battery...

BTW, whether you want a 25hp or 72hp engine is determined 
by the choice whether you want this to be mainly an EV
with a range extender that can allow it to get home even when
the battery fails and allow it to make unlimited trips with 
some limitations to continuous power use (no 100 MPH stints, 
only 65-70 continuous allowed)
or that this should be a regular gas car with its performance
that can maintain 100 MPH constant and have EV boost for the
extra power and possibly for short trips...
Which way do you want to roll the design?

EV+ or gas+?

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Larry Gales
Sent: Monday, August 22, 2011 11:47 PM
To: SEVA; Electric Vehicle Discussion List
Subject: [EVDL] A less complex Chevy Volt?

Using the following equations:
Rolling Resistance RR = rrc * weight
Drag = (0.5) * (rho) * (v**2) * Cd
* A
HP = ( Drag + RR) * V)/550

I compute that a car like the Chevy Volt needs only about 20 HP to
cruise at
65 MPH on a
flat road with no wind. Yet I understand that the Volt actually uses a
72 HP gasoline engine:
almost 3 times as large. It appears to me that Chevy tried to do 2
things:

o Produce a series hybrid car with absolutely NO compromises
compared with a gas engine car:
it can cruise for hundreds of miles at a sustained 100 MPH -- way
beyond what is needed.

o Create a drive train that achieves the maximum possible
efficiency.

This combination of objectives can only be met with a very complex and
expensive setup. I have looked at aspects of the Volt drive train and
it seems WAY more complex than a typical electric car.

So I wonder if the following approaches would be workable:
o A pure series hybrid where you have a fixed RPM gas engine of about
25 HP which turns on
when the battery gets below a certain amount (it can also be turned
on by the driver at will)
and which simply feeds juice to the battery equivalent to the drain
on the battery when it
is traveling at 65 MPH. If the car is traveling faster, or up
hill, etc, the battery level
will start to drop, but when the the car travels slower, downhill,
etc, the battery level
will start to rise again.

I realize that there is about a 20% loss with energy going in and
out of the battery, but
if the current Volt gets 40 MPG on its gas engine, this approach
should get 30-32 MPG
for a very much less complex and expensive system. There would
also be some occasions,
such as VERY long hills (e.g., mountain driving), or persistent
headwinds, where the car
could not continue at 65 MPH but would have to slow down to 50-60
MPH or less, but these occasions
should be comparatively rare, but in any case the car would have
unlimited range (within its
gasoline fuel supply).


o Another series concept is whereby a fixed RPM engine sends
electricity to BOTH the electric motor
and the battery: if the car needs more HP, it adds battery power
to the electricity coming from the
engine, but if it needs less HP, more of the engine produced
electricity is sent to the battery.
This appears to be more efficient, but also more complex then the
design above, but if the added
complexity is electronic, rather than mechanical, it might not be
too bad. I believe that the
current Chevy volt does something like this but than adds the
mechanical complexity of a direct
mechanical connection between the gas engine and the actual wheels.


So a much simpler and less expensive setup should produce a car whose
peak performance is the same, and whose sustained performance is
adequate for the great majority of time.

I would appreciate any feedback on these concepts.

-- Larry





--
Larry Gales
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| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
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_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

> On 22 Aug 2011 at 23:46, Larry Gales wrote:
> 
> > So a much simpler and less expensive setup should produce a car whose peak
> > performance is the same, and whose sustained performance is adequate for the
> ...


----------



## EVDL List (Jul 27, 2007)

The car should not suddenly lose power when the battery is empty,
it is easy enough to gradually reduce the max sustained output
with the level of the SoC going down so that there are no
surprises. You don't get rear-ended because you drive too slow,
otherwise there would not be a tractor trailer without constant
other vehicles crashing into it, but the problem is unexpected 
and large changes.
So, just gradually reduce the power, a short hill you can climb
at 70 MPH if you want.
A long hill you can start climbing at 70 MPH, after some time
the power gradually reduces, so you see the needle slowly creep
to lower speeds: 65, 60, maybe as low as 55 if the grade is
steep enough and that is the max that the ICE/generator can do,
because in the end the battery is not contributing any longer.
I have driven plenty cars that had trouble with steep hills,
losing some speed going up is not a problem unless you make it
a defect in your mind. As you say, plenty cars can have
limitations and sometimes this is countered during the sales
process, where the salesman asks if you expect the car to go
up steep hills at full power. Oh! But then you need the xx hp
version, it only costs xxx more for the more powerful version...
People who don't need to climb hills or who accept the
performance don't get the "upgrade".
The base variant is what sets the advertised price...

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of EVDL Administrator
Sent: Tuesday, August 23, 2011 4:26 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] A less complex Chevy Volt?



> On 22 Aug 2011 at 23:46, Larry Gales wrote:
> 
> > So a much simpler and less expensive setup should produce a car whose
> > peak performance is the same, and whose sustained performance is
> ...


----------



## EVDL List (Jul 27, 2007)

This is part of where the "Mountain Mode" of the Volt comes in. What happens
when you put in in "MM" is that it fires up the ICE instantly to make
electric, saving the batteries for later when you know you have a large
climb coming. This helps wear and tear on the DoD as well.



> Cor van de Water <[email protected]> wrote:
> 
> > The car should not suddenly lose power when the battery is empty,
> > it is easy enough to gradually reduce the max sustained output
> ...


----------



## EVDL List (Jul 27, 2007)

> Cor van de Water <[email protected]> wrote:
> 
> > I have driven plenty cars that had trouble with steep hills,
> > losing some speed going up is not a problem unless you make it
> ...


----------



## EVDL List (Jul 27, 2007)

> Zeke Yewdall wrote:
> >
> > On Tue, Aug 23, 2011 at 5:55 PM, Cor van de Water
> > <[email protected]> wrote:
> ...


----------



## EVDL List (Jul 27, 2007)

To clarify a few points here:

(1) The HP of a gas engine in a Volt-type series hybrid has *NO* effect on
the peak
performance. As long as the battery is between 35%-85%, it is
supposed to be pure
electric, so it does not matter if it has 1 HP or 100 HP.

The HP for the gas engine only affects how LONG it can perform at a
given speed,
at least for the first option I specified.

(2) An option 1 pure series hybrid is indeed much simpler than the Volt.
Think of it
as a Leaf with a range extender engine that just feeds the battery. I
believe that
the Leaf has a total of something like 5 moving parts in its entire
drive train.
Most new EVs either have direct drive or just a single reduction gear
between the motor
and wheels -- they don't even need a reverse gear as they run the
motor backwards.

In contrast, parallel hybrids (and the Volt has become something like
a parallel hybrid)
have the full complexity of a gas engine drive train, an electric
motor, and
a complex interaction between the two systems. I think I read
somewhere that the Volt software has millions
of lines of code, even more than a large airliner. Here are some
details from this URL:

http://www.plugincars.com/exclusive-chevrolet-volt-chief-engineer-explains-volt-drivetrain-says-volt-electric-vehicle-90758.ht

* Farah says that in his mind the Volt is unequivocally an
electric car. "The Volt is
an electric vehicle...because for the first 40 miles you can get
full performance running on
nothing but an electric motor until the battery is depleted," he
said.
* The Volt has three distinct motive forces in it: a large
electric motor, a small electric
motor/generator, and a 1.4 liter engine. Up to two of those
three forces can be combined in
select ways through the Volt's secret sauce drive unit.given the
road demands and state of
charge of the battery.to drive the vehicle.
* Only the large electric motor is capable of moving the car
forward on its own. The small
electric motor/generator and the gas engine can only ever be
combined with one of the other
motive forces to drive the wheels.
* Even when the gas engine is on and partially driving the wheels,
it cannot operate without
electricity flowing to one of the other motors.
* The gas engine, under most conditions, will be used to drive the
generator and produce

* There is no "direct" mechanical linkage between the Volt's gas
engine and the wheels,
rather there is an indirect linkage that is accomplished by
meshing the power output of the
engine with the power output of one of the other two electric
motors.
* Motor Trend's reporting that the magic cutoff speed of 70 mph is
what the car uses to
determine whether or not to make the engine to partially drive
the wheels is incorrect. The
engine is used to partially drive the wheels when the car
calculates that it will be a more
efficient use of the engine's power. There is no hard cutoff
point.

Frankly, this looks very complex to me. Just Google "Chevy drive
train" for more details. See


http://www.plugincars.com/exclusive-video-want-know-exactly-how-chevy-volt-powertrain-works-95344.html

for a video of the Volt drive-train.


(3) As someone else mentioned, there is nothing extreme about
selective vehicles having to slow down
under certain circumstances: buses, trailers, and trucks do it
all the time on hills, and we manage to drive.
Just as gas engine drivers don't ignore their gas gauge, EV
drivers are even more attuned to the
state of their battery, and will gradually slow down if the need
arises -- and most of the time
the need will not arise.

-- Larry Gales



> Larry Gales <[email protected]> wrote:
> 
> >
> > Using the following equations:
> ...


----------



## EVDL List (Jul 27, 2007)

> On 24 Aug 2011 at 19:40, Danpatgal wrote:
> 
> > It seems like we should be lobbying for higher fuel taxes (that could
> > be used to fund EV research) than building the machines themselves.
> ...


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