Breaking news! Chevy volt technically driven by gas engine!

[cfg83]

Neil -

Originally Posted by NeilBlanchard

...

It only requires two or more power sources i.e. two kinds of motors.

Motor Trend Claims Volt Gets 127 MPG, Not Quite True – Gas 2.0

Yeah, plug-in Prius' have made similar claims :

CalCars' PRIUS+ Plug-In Hybrid

- The Calcars first proof-of-concept: (100+ mpg plus electricity, 10-mile electric range, now with temporary lead-acid battery pack, soon to be replaced by nickel metal-hydride batteries).

- Two EDrive/EnergyCS prototypes: (100+ mpg plus electricity, 30-mile range, with lithium-ion batteries.

I think that regardless of our debate, the term "hybrid automobile" has come to mean an ICE+Something drivetrain, that something being battery assist at the moment.

CarloSW2

[NeilBlanchard]

EV WORLD CURRENTS: Tempest in a Teapot

As the paper describes it, the Volt has four driving modes: single motor EV, two motor EV, single motor extended-range, two motor extended range combined. The single e-motor (EM1) is used to launch the vehicle and operate at it lower speeds. It can develop 111kW of power, giving the car brisk acceleration. For high-speed EV-only travel, the electric generator that is attached to the IC engine, converts into an electric motor (EM2), providing additional torque to propel the vehicle using battery power only.

It is only when the battery is depleted below 45% state-of-charge (SOC), that the IC engine fires up and the second electric motor (EM2) reverts back into a generator, producing enough electric power to propel the car another 300+ miles. State's GM's technical brief:

Regardless of which drive mode is used, the Volt is always propelled with electric power delivered by the traction motor. The engine cannot propel the Volt unless the traction motor is also running. In order for a planetary gear-set to transmit torque, at least one of the three main elements (ring gear, sun gear, or planet carrier) must be able to be locked or held. Since there is no clutch to lock the sun gear, the traction motor must be used to provide the reaction torque needed for propulsion.

According to GM, "this unique propulsion architecture allows the Volt to achieve 10-15 percent better efficiency at highway speeds than would have been possible by using only the single traction motor."

(Emphasis is mine.)

Using a very complex system of planetary ring and sun gears, plus three clutches and two electric motors

(Emphasis is mine.)

So, the Volt could be a series hybrid without a battery at all. It is a series/parallel/split hybrid and it does not need a battery to be any of those.

Is it a car with a hybrid drivetrain, or isn't it? Does it need to be a plug-in to be a hybrid, or not?

[dcb]

I think this part validates my parallel at cruise argument:
"According to GM, "this unique propulsion architecture allows the Volt to achieve 10-15 percent better efficiency at highway speeds than would have been possible by using only the single traction motor."

[cfg83]

Neil -

Originally Posted by NeilBlanchard

...

Motor Trend Claims Volt Gets 127 MPG, Not Quite True – Gas 2.0

That URL led me to this table :

127 MPG: The Chevy Volt Diaries - Real World Experience - Motor Trend


The article stated that the Volt has a 16 kWh pack, but will only use 8.8 kWh of it's juice before turning to the ICE, which is the same as going from 85% down to 30% of charge capacity :



Then I used this gallons-to-kWh converter :

Convert US gallon of gasoline to kilowatt hour
Convert gallon [U.S.] of automotive gasoline to kilowatt-hours - Conversion of Measurement Units

To make this table :



I only used the numbers from the days when the pack was fully charged, the idea being that all 8.8 kWh was being used up in that day. That led me to 147 MPGe.

When I plugged that number into the total miles, I got an average of 78 MPG :



Now, obviously that is not a complete analysis because the data is incomplete. I can't see the % drop in the state of charge for each day. However, I think it is an attempt to make a *fair* calculation of MPG.

CarloSW2

[NeilBlanchard]

Here's the X-Prize spreadsheet: http://www.progressiveautoxprize.org...Calculator.xls

If you say 35.2 kWh for the first four trips, and no electricity for the last five, and count the 2.36 gallons of gasoline, with the total distance at 298 miles, that spits out 88MPGe.

[NeilBlanchard]

Coincidentally, Robert Llewellyn got 87MPG on the Prius plug-in on a 300 mile trip with three charges. Obviously, the much smaller pack on the Prius only goes 12-14 miles in EV mode, so the Prius beats the Volt handily in MPG with the ICE running!

I wonder what the charge times are for the Volt vs the Prius? It would be near impossible to charge the Volt more than twice in a 24 hour period, whereas the Prius might squeeze in 3 or 4 charges in that time?

Advantage: Prius plug-in.

[dcb]

There was a fudge figure of ~50mpg in range extended mode initially, looks like 35mpg is what they are saying now. To me that is the only way to evaluate it that won't make peoples heads explode with complications and assumptions and bs.

[rmay635703]

Originally Posted by dcb

that won't make peoples heads explode with complications and assumptions and bs.

My head didn't explode, I just didn't want the car.

That said

I wonder if anyone on the DIY side has made a range extender SINGLE speed small gas turbine generator. The military makes them up to 52% efficient, a normal car is only 5%-20% efficient when run over its load range under normal driving conditions. (abrupt stopping removes the efficient part on everything but regen)

My EV with a nice 5hp single speed single output generator could travel basically indefinately at 25mph if the generator and controller were decently efficient. It would seem moving a small motor generator from roughly 14-20% efficiency to 40-50% eff would cause a series electric to be much more energy efficient at low speeds than a typical gas powered car or even a typical hybred powered car.

Anyone want to make or source something to convert an EV into what the volt should have been, and no I'm not talking adding an 1995 1800watt coleman 4 cycle on the back.

Hmm, subaru made my little 360 into a 100mpg car.
http://www.drive.subaru.com/Sum06_attic3.htm

Cheers
Ryan

[dcb]

why not hook that 5hp motor to a 5th wheel and stick it in your tow hitch with a lever to raise/kill it or lower it?

[rmay635703]

Originally Posted by dcb

why not hook that 5hp motor to a 5th wheel and stick it in your tow hitch with a lever to raise/kill it or lower it?

To achieve 50% efficiency you CAN NOT DO THAT, period!
Those motors are designed to work at ONE OUTPUT SPEED AND POWER VALUE.
Motors that vary output tend to all universally be below 30% efficiency, most being below 25% in real world. (and thats modern fuel injected, not a small gas engine)

If you DID do that with a single speed turbine you would move below 30% efficiency in a heartbeat, in fact most ICE engines in stop and go are only really about 5-10% efficient when not driven by a hypermiler.

Classic gasoline motors were always assumed to be about 13-17% efficient motor to wheels as an example mainly because they rarely operate at their efficient area. A 5hp standard motor is typically in that range as they are usually antique in their controls and tend to go rich during their operation.

Moving motor burn efficiency from maybe 25% (likely lower on a SGE) to 50% of a single speed turbine would do the most to improve fuel economy in that application.

Thus a generator powering an electric motor decoupled so it could only run at its most efficient range could likely still operate about 65% more efficiently (even with losses) than a classic variable throttle motor running through some sort of gear reduction system.

The battery losses would be hopefully very very neglidgable because the generator would normally be dumping its full rated load into the motor directly.

Cheers
Ryan