GM-VOLT : Chevy Volt Electric Car Site

I have been driving a Chevy Volt since November 11, 2010, covering over 4200 miles so far.  Almost all of this driving has been in winter conditions.  I logged my first 2352 miles here to get a feel for the vehicle’s overall efficiency, which effectively settled in at 129 miles per gallon.

For the entire month of January I have recorded my daily EV range compared against ambient temperature, driving style, road consitions, and HVAC cabin energy use.  I started each day with a fully charged battery and my trip was 30 miles one-way.  I did not pre-condition the cabin and 90% of the drive was at highway speeds over 65 mph, using Normal mode acceleration and L-position motor braking.

The data is presented below:

Date	Temperature (F)	Driving Efficiency	Cabin Efficiency	EV Range	Notes
12/30	30	66%	13%	27
1/2	28	64%	15%	25.6
1/5	36	69%	18%	24.7
1/6	28	73%	12%	25.6
1/7	32	66%	15%	23.4	snowing
1/10	33	60%	45%	25.6
1/17	22	68%	12%	26.4
1/18	32	66%	16%	22.8	slippery ice
1/19	38	83%	28%	27.9
1/20	34	89%	32%	31.2	72 eco
1/21	29	79%	21%	27.2	icy
1/24	8	68%	6%	26.6	0.1gal used due to temp

You will notice the columns called driving and cabin efficiency. The higher the number the more efficient.  These were obtained from the dashboard display at the point the gas engine went on.  It is posible to achieve 100% driving efficiency if one stays below 50 mph and is very careful to avoid accelerating and braking hard, trying to coast as much as possible, something I did not achieve in my particular commuting cycle.

The cabin efficiency reaches 100% if no HVAC is used, the lower the number the more aggressive the HVAC settings.

Over this period my average EV range was 26.2 miles with an average driving efficiency of 71% and cabin efficiency of  19.4%.  The average temperature was 29.2 degrees.  EV range appeared further reduced when the roads were slippery from snow and/or ice.

My greatest range was 31.2 miles at 89% diving and 32% cabin efficiency, and the lowest range of 22.8 miles occurred at 66% driving and 16% cabin efficiency.

On of the benefits of driving the Volt is the free five year OnStar subscription.  For the Volt, OnStar is particularly feature-rich as it monitors the health and functioning of the car and its components, as well as keeping track of its ongoing energy consumption.

I started driving my consumer advisory board Volt on November 11, and had been waiting for my first full month report to post it here.  I received my first detailed  full month’s OnStar Vehicle Diagnostics report on January 10th reflecting the driving behavior of the preceding 30 days.  The information is displayed in the graphic above.

According to the report, for that period I drove the car 3443 miles. Of those, 2432 were on electricity and 1011 were on gas, indicating that 71% of my miles were electric.

Overall gas fuel economy for the month was 114 mpg, and it was estimated that by using electricity I saved 103 gallons of gas.

A particular interesting number the system determined was that my electrcity consumption was 19 kwh per 100 miles. The system also claimed by driving the Volt 2,014 pounds of CO2 production were avoided.

During the month of January, the weather was quite cold and I used comfort mode cabin setting with a temperature of 74 degrees plus one bar of heated seats. I also drove mostly at highway speeds and experienced typical EV driving ranges in the high 20s.

I charged to full every evening at 240-volts and opportunity charged during the day at 110-v anywhere from 6 to 8 hours. It is known the Volt will draw 12.9 kwh of grid energy to replete the 10.6 kwh of battery power used for the full EV driving range.

These data confirm the success of the Volt as a highly flexible vehicle without compromises that can displace substantial amounts of gasoline consumption, utilizing electricity efficiently and less expensively to do so.

The EPA has determined through testing that the Chevy Volt would go a typical 35 miles on a full battery charged.  Using the full 10.4 kwh of stored battery energy available, GM has determined the majority of drivers will experience from 25 to 50 miles of range.

There are several examples in which journalists and fellow advisory board drivers have gotten more than 50 miles of range in their Volts.

Today I report on my first experiences just barely crossing or not even reaching the 25 mile threshold when the engine came on.

This first time I left home on my typical daily commute with a full charge.  It was a cold day of 32 degrees outside.  I had the cabin temperature set to comfort mode of 72 degrees with a medium fan speed and one bar (out of three) on the heated seat control.

My drive is almost all highway with 65 MPH speed limit.  I traveled mostly at that speed plus or minus a few miles per hour, and was using the Normal as opposed to Sport mode setting.  Mostly I kept the car in D, or coast brake setting.

At about 11 miles into my journey I hit standstill traffic resulting from an accident on the highway. Helicopters were circling and I spent about 40 minutes in a very minimal crawl as two lanes were funneled into one in which extensive rubber necking took place.

During the stop and go portion I left the car in L mode to use motor braking, and covered about 4 or 5 miles.

After, traffic moved smoothly, and I arrived to my office parking garage just feet from my parking spot and waiting outlet when the generator went on at 25.3 miles.

On warmer days I would have arrived with about 8 miles to spare, indicating the significant drain from being in standstill traffic for 40 minutes with the cabin temp cooking.

Thus my first experience only getting 25 miles per range had less to do with extreme cold temperatures or aggressive driving style, but more to do with unexpected traffic.

On two subsequent driving days, I experienced just below 25 miles of range, with the lowest being 24.4 miles.  These days were colder, in the low 20s, and included a bit more use of the Sport mode, though not continuous.  In neither case did I drive meaningfully above 70 mph.  The day with the lowest range included a 20 minute traffic jam.

Most recently I drove to work after the Northeast snowstorm and several of my low speed roads were a bit thickened with snow.  This extra tractive effort seemed to drain a lot from the battery.  The temperature was again about 30 degrees and this time I kept the cabin at 74 degrees of comfort mode.  I did not use Sport mode at all and kept my speed around 65 MPH.  The engine went on after 22.7 miles.

Using aggressive cabin heating combined with high speed highway driving in sub freezing weather may lead to electric ranges of less than 25 miles.

Drivers of the 2011 Chevrolet Volt have three driving modes to choose from; normal, sports, and mountain mode.

The mountain mode is rarely used.  It acts to cause the range extender turn on at higher charge point of the battery.  This allows a deeper battery reserve for use when travelling up a long steep grade.  In nearly 2000 miles of driving I have never found the need to use it.

When the car is powered on it is in regular mode by default.  This provides a standard accelerator experience. Pressing the drive mode button twice causes the car to shift into sports mode.  Once engaged the driver will feel the car surge forward, and it becomes much more spirited in acceleration.

GM Volt director Tony Posawatz once mentioned that the car would get the same efficiency or EV range whether the driver was in sports mode or regular mode.  Top power out put is the same 110 kw, and flooring the pedal produces the same response in both instances.

“On the various EPA federal test procedure cycles, the efficiencies are basically the same, says Posawatz.

It is true, though that driver behavior is a more prominent factor.  Aggressive use of the accelerator in sports mode will lead to more range reduction than the same use of the accelerator in normal mode.

“Sport mode may cause you to have a bit more fun and if you fully realize the fun opportunities, you will be a bit less efficient,” says Posawatz.

In my experience driving the car, I tend to prefer sports mode, and use it all the time.  Tony Posawatz also drives a captured test fleet Volt and uses it a bit differently.

“I have found that I use Sport mode and have fun when I know that I will make it to my charging station without using gas and with time to charge,” he said.  ”It is my guilty pleasure.”

“Similarly, I have changed my driving a bit to see if I can beat the “video game” and improve my numbers,” he added.

Braking is another issue.

When in D mode, the car softly coasts similarly to a conventional car when the foot is off the accelerator. L mode engages a strong regenerative drag when the foot is off the accelerator that allows the driver to simulate a downshift effect and get motor braking, sparing the disc brakes from wear.

It has been my preference to drive at speed in D mode, but when needing to slow or in stop and go traffic I use the L mode.

Posawatz explains that overall efficiency doesn’t differ much between these two settings either.

“Relative to D vs. L, there also is not a lot of difference in efficiency between the two,” he said. “Going down Pikes Peak, you want to be in L.”

“You want to use the coast of drive and then shift into L as you approach a stop, he added. “I use the L a lot because it is a more engaging drive, especially in Sport and on winding roads.”

With the release of the EPA testing result we finally have a good idea how much electrical energy the Chevy Volt will consume.

Its lithium-ion battery back contains 288 cells which combine to a total of 16 kwh of energy storage capacity when full.  From the days of the concept GM said it would only use half of that energy to travel 40 miles, keeping the rest as a gradually receding buffer to keep the battery healthy.  Over time engineers realized they were comfortable using more of that energy safely.

In the final configuration, according to GM’s Director of Battery Systems Mickey Bly, “we moved the state of charge usage from 50% (8kwh) to around 65% (little over 10kwh) during the development and validation phase as we learned how capable this battery really was.”

Sixty-five percent of 16 is 10.4 kwh.

That is the exact amount of energy the Volt has at its disposal to complete its full range of pure electric driving.  The EPA has determined that will be 35 miles on average. They also report that energy use works out to 37 kwh/100 miles, or 2.7 miles per kwh.  This will depend on driving style, cabin climate control use, and terrain.  Most people will see between 25 and 50 miles of range.  In my experience at mostly high speed highway driving, I range from 32 to 38 miles of range (40 degrees outside and 72 degrees cabin mostly).

One member of the Volt consumer advisory board was able to get more than that when he really tried.  ”The most miles I drove on battery mode was 53.8 miles,” said NY CAB member Robert Becker. “It was 53 degrees outside during the trip.”

“I made an effort to drive as efficiently as I could during this trip,” he said. “I tried to keep the car between 40 and 50 mph and used as little braking as possible during the trip.”

The lowest range I have gotten was 31 miles when I was really hightailing it in the 70-75 mph range on the highway in sports mode and using 72 degree comfort mode HVAC setting on a 32 degree day.

It turns out, however, that the energy in the battery isn’t all the energy the car consumes.  The EPA’s testing shows that the car will consume 12.9 kwh from the grid to fully recharge a depleted battery, considerably more than the aforementioned 10.4 kwh.

“On the EPA rating of 12.9 kwh used, you need to remember they are measuring total energy pulled out of the wall, not what makes it to the battery,” said Bly.  ”(This is) so you know your consumption on electricity.”

“There are losses from the house to the battery from transportation and conversion over the cords, charger, conditioner, and inverter,” he added.

Thus when determining the cost of electricity in driving the Volt one must use the cost of 12.9 kwh divided by the total number of miles it allows you drive, even though the car is going those miles on only 10.4 kwh of on-board energy.

The last thing we have been waiting for is finally here: the 2011 Chevrolet Volt official EPA fuel economy and label has been revealed.

On Wednesday the EPA released the information to GM who then immediately announced it publicly. Now the cars can be delivered to customers, allowing the company to achieve a hole in one for a delivery date first anticipated over three years ago.

Here are the official numbers:

1. 93 MPGe for all-electric range, combined city highway. This is expressed as miles per gallon equivalents showing how far the car can drive purely on the amount of electric energy that would be contained in a gallon of gas (33.7kwh)

2. Official full charge time is 4 hours at 240-v

3. EV Range is 35 miles officially, GM still says 25 to 50, based on driving style, temperature, and terrain.

4. Extended range charge-sustaining combined city and highway fuel economy is 37 mpg. It is 35 mpg city and 40 mpg highway.

5. Total range is 379 miles, 344 of gas range plus 35 miles electric range.

6. 60 MPG is the official overall combined number (MPGe + MPG) of fuel economy behavior over lifetime of the vehicle. It would be 93 if driving purely electric and 37 if you only drove using gas. This is the highest, of course, in the segment.

There is also a table on the label showing the consumers’ cost based on how far they drive each day and how much they are able to charge. We also find the car is using 12.9 kwh during for its 35 miles of electric range.

Of course the distance the driver goes between charges and how frequently the car is charged will significant determine overall fuel efficeint. In my example I have driven the car over 800 miles and am achieving about 150 MPG.

These are the examples given in the table:

30 miles N/A (10.9 kWh consumed)
45 miles 168MPG (12.9 kWh consumed)
60 miles 89MPG (12.9 kWh consumed)
75 miles 69 MPG (12.9 kWh consumed)
No Charge 37 MPG (35 city/40 hwy)