[ad#post_ad]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.
This entry was posted on Friday, December 3rd, 2010 at 7:15 am and is filed under Battery, Efficiency. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.