GM-VOLT : Chevy Volt Electric Car Site

The Chevrolet Volt has at its disposal the ability to thermally pre-condition the cabin using grid-supplied electricity while it is plugged in.
This feature is useful both in hot and cold days to turn on the AC or heat respectively.

In the Volt the owner can turn on the cabin HVAC either by using the remote smartphone app or via the MyVolt.com website.

The idea is to use grid electricity to heat or cool the cabin to avoid battery-stored power to do so once the trip commences. It uses more energy to get the cabin to the desired temperature than it does to maintain it there.

Pre-conditioning does require a bit of forethought to turn on the cabin HVAC in preparation for driving, something in paractice I often don’t remember to do. Programming it to happen automatically or being able to choose the temperature remotely would be useful features that do not exist.

A new study by the National Renewable Energy Laboratory (NREL) may provide more motivation to remember.

NREL engineer Robb Barnitt led a study in which researchers simulated the effect of cabin preconditioning on PHEVs and HEVs in various different drive cycles and ambient temperature scenarios.

“We knew that climate control loads would have an impact on CD range, but were surprised by the magnitude” Barnitt said. “We found that climate control loads can reduce CD range by 35%, but that thermal preconditioning can partially restore CD range.”

The study examined the effect of temperature and preconductioning on electric range for a 100 mile BEV (i.e. LEAF), a 15 mile PHEV (i.e. plugin Prius) and a 40 mile sreies PHEV (i.e. Volt)

In the case of the PHEV-40, using heat reduced range by 35.1% and using AC reduced range by 34%. Preconditioning with heat increased range by 5.7% and preconditioning with cooling increased range 4.3%.

In a pure EV range reduction from heating and cooling were similar, though the magnitude of increase through preconditioning was less. Range increase through preconditioning was highest in the PHEV15 where 19% was predicted.

You can read the entire study in detail here (PDF).

Moral of the story. Pre-condition your Volt.

Source (NREL) via (GreenCarCongress)

GM has partially lifted the veil on how they go about testing cars in hot weather environments in the latest example of Volt development transparency. This week engineers have been putting a fleet of Volt prototypes through extreme heat testing in GM’s Desert Proving Grounds in Yuma, Arizona.

Hot Soak Evaluation
In this test the Volt is baked all day on black top pavement in direct sunlight and 96 degree temperatures. Lead durability test engineer Steve Pratt measured the interior air temperature of the car at 138 degrees. He went on to check for squeaks and rattles that might be created by the heat, both while standing and driving, and finds none.

He also test the ability of the AC to quickly cool the car to acceptable levels and finds it does so satisfactorily.

“Things went very well,” he said.

Grade Load Testing
In this case GM engineers evaluated the car’s performance at continuous climbing in high heat. To simulate a continuous grade, engineers hitch a towing dynamometer to the rear of the car and drive around a circular track (see graphic above). The dyno can simulate a continuous grade of anywhere from 2 to 10 percent, and on this test they looked at 5 and 7.2 percent at 106 degrees F. The test checks for overheating and how the car handles the stress and strain on what amounts to an endless mountain.

Pratt’s team also took the cars up a 7000 foot climb in Arizona in range extended mode and found they “performed excellent.”

Of note GM doesn’t not recommend using the Volt to tow.  Engineers had to remove part of the rear fascia to hitch the dyno.

City Cycle Testing
In this test GM engineers take Volts into continuous city cycle repeated driving under high heat circumstances. Once again the point is to look for car failures in the grueling heat with particular respect to overheating or electrical disruptions.

Once again, the car handles this testing well.

Trailing Dust Test
In this test the Volt follows behind a Chevy Silverado for 12.2 miles and the truck kicks up desert dust. Engineers then screen for intrusion of the dust into the vehicle through door seal, vents, and other filtration systems. Success on that one too.

Pratt says in his 15 years of running this test, “the Volt is is one of the best cars he’s ever tested” on this course.

Road Schedule Temperature Profile
This checks for real-world pressures and temperatures in the fuel tank at high temperatures. It is done on a 72 minute cycle at 40 percent capacity and ensures fuel is not improperly evaporating.

As GM sums up the experience in a statement, “the Volt has performed very well under the stress and strain of all these tests, but the rigorous testing and validation continues because the Volt is an electric vehicle for all temperatures and seasons.”

The extreme heat testing adds to the suite of previous tests GM has already put the Volt through and shared with us.  This includes extreme winter testing and mountain climbs such as Pike’s Peak.  The car is on track for retail launch now little more than four months away.

Source (GM)

There are two major reason why people want electric cars. To achieve energy independence, to help the environment, or both.

While the first benefit can’t be disputed, a newly publicized study suggests that electric car use may actually be worse for the environment.

The study was performed by the group Transport Watch and found that diesel cars produce half as much CO2 as electric cars when the fossil fuel required to make the electricity is taken into account.

The study concludes “We conclude that the notion that electric cars will reduce emissions is a fiction.”

The study also took into account electrical energy leaked lost between the powerplant and the point where the vehicle would be charged. This leakage was estimated to be an astounding 76%. Diesels on the other hand achieve a 45% efficiency.

The research was done in the UK where only 20% of electricity is generated by renewable energy. It was estimated that in China, for example, where most electricity comes from coal, a change from diesel to electric vehicles would double CO2 emissions.

The research implies that burning fuel within the vehicle produces less emissions than creating electricity and sending it down the grid.

A conclusion drawn from this research by Philip Gomm, of the RAC Foundation is; “Electric vehicles are not a panacea. They are good for generating headlines but not necessarily at saving the planet, at least not in the short term. For today and tomorrow, a lot more attention needs to be paid to refining existing petrol and diesel technology, and making cars smaller and lighter as a way of saving fuel – something recognized by the Committee on Climate Change. These are proven solutions to an immediate problem.”

You can check out the details of the study here and draw your own conclusions.

Source (Telegraph)

To this day people new to the Volt concept continue to draw the conclusion that it should have solar cells on its roof.

Here’s an email I just got today:

THE NEW CAR THE VOLT.WHY DIDN’T YOU PUT SOLAR PANELS ON THE ROOF. IT WOULD CHARGE THE BATTERY WHEN IT SAT OUT SIDE IN THE SUN??????????

The idea that a small panel of solar cells sitting on the roof in sunlight even for hours could do much to actually recharge the battery and justify its expense are unfortunately unrealistic at the present time.

However, the public “green-demand” for it has led GM vice chairman Bob Lutz to infer that a solar roof could be a Volt option. It was supposed to be shown at the Detroit Auto Show, but never made an appearance.

Toyota though, rode the PR wave and introduced a solar roof option for its new 2010 Prius, which is base-priced at $22,000, gets combined 50 mpg fuel efficiency, and went on sale in May.

Here’s how Toyota describes their solar panel option which retails for $3500:

An available sliding glass moonroof is packaged with solar panels, located over the rear seating area, that power a new ventilation system. This solar powered ventilation system uses an electrically powered air circulation fan that does not require engine assist. The system prevents the interior air temperature from rising while the vehicle is parked, making the cool-down time shorter when the driver returns to the vehicle, thus reducing the use of air conditioning.

Check out the following video and see how that Prius solar panel roof actually works out in real word testing:

The following is a recent exchange I had with Volt vehicle line director Frank Weber concerning battery temperature control in the Chevy Volt.

Does the battery always have some electronics running, even when the car is turned off?
No, there is a real sleep mode.

Did you hear about former CEO Martin Eberhard noting his Tesla Roadster was constantly burning energy when it sat in the garage unused?
Yes, his refrigerator. We don’t have this problem.

What we also will do is we will condition that battery for a certain period. When its plugged in and charging, and its really really cold, then you would probably spend a fraction of your grid energy just to keep your battery conditioned so that you can leave your garage or house in very very low temperatures, driving electrically.

What if you leave your Volt outside in the extreme cold?
You could still do this. The battery is fully insulated. Keeping the battery temperature for a while. To keep it just above freezing it can drive electric. Also the car will be smart. If you don’t use your car at some point you don’t want to spend energy anymore. At that point it will just stop conditioning.

The car will know that? Say if you leave it unused for a week?
No one will want to condition the battery for a week. What’s happening at low temperatures depends on what the state of charge is, we haven’t seen any major sensitivities. This car could sit there for two weeks, but without conditioning it again, it certainly wont start on electric. The engine would start and condition the battery for a few minutes.

So is there a delay when the car decides whether to start on gas or electric?
It would know this within a fraction of a second. The moment you open the door, the calculation starts, what is the battery temperature, what is the outside temperature and how should the car start.

So the gas engine will then heat the coolant?
It will propel the car and it will condition the battery. The moment you are running the engine you have the electric heater running in the battery.

So there is an electric heater in the battery?
Yes, you can chill and heat the battery.

Do you need to keep the battery at room temperature the whole time it is operating?
You don’t have to condition it to that level.

Can you say how low a temperature can the battery go on at?
No. A certain operating window that you have. You don’t have to always keep it at 71 degrees F. Ideally that is the temperature you would like it because that is where you have the maximum power output of the battery and you have the best life expectations.

The Chevy Volt has been designed to be able to drive for 40 miles on stored electricity when starting from the point of a fully charged battery. GM has specifically engineered the car around that goal. That range is based on a certain set of assumptions, which includes reasonable driving aggressiveness. Severe aggressive driving with frequent hard accelerations would be expected to reduce the electric-only range.

A question not fully answered is how air conditioning might affect range, considering how highly energy- demanding an application it is.

I recently had the chance to ask Frank Weber who is the Volt vehicle line executive.

Would you say running air conditioning at high capacity will reduce your electric range in the Volt?
It will.

Can you say how much?
It is so dependent on the ambient temperature and what your setting is.

How about maximum A/C on a hot day?
We haven’t discussed that (publicly).

Will it be less than 40 miles?
Absolutely. Physics are physics. Its like the electricity bill at your house. The moment you decide to switch the air conditioning on, it is a conscious choice that you will pay for it.