Driving 190 electric miles in a Chevy Volt blows up 35 mile range myth
Does the 35 miles (or so) electric range of the Chevy Volt mean that Volt owners are limited to 35 miles of electric driving per day? Over the weekend a Florida based Chevy Volt owner, Edward Ellyatt, excitedly reported having driven 190.6 electric miles in one day with his Chevy Volt. That's way beyond the 35 mile electric range limit. He is part of a group of Volt owners using the website, VoltStats.net, to share mileage results, achievements and friendly competition with each other to see which of them can make the most of the Chevy Volt.
The Chevy Volt's 35 mile electric range is a factoid used by some of the Volt Naysayers to dismiss that car. What Ellyatt did last weekend was to blow up, and demolish, another electric car myth. Even a car with as short an electric range as the Volt can accomplish a significant chunk of electric driving in a day.
The Chevy Volt is a plug-in hybrid electric car, where the battery pack allows a 35 mile or so electric range, with the gasoline engine providing power to extend the total driving range. GM's design goals for this dual drive train is to fit into the typical daily driving pattern. Research shows most people drive 40 miles or less per day, meaning the Volt's 35-40 mile electric range will handle typical daily driving tasks, and the gasoline engine is a backup to extend range and prevent range anxiety.
What makes Ellyatt's accomplishment interesting is that it goes beyond the math of Chevy Volt Recharging. A full recharge of the Volt's 14 kilowatt-hour battery pack, after the 35 miles (or so) of driving, requires 4 hours or so at a J1772 charging station. Scribbling on the back of an envelope we calculate that 190 miles of electric driving would require 6 recharging sessions, each requiring four hours or so, meaning as many as 24 hours of recharging time, leaving one to wonder just how Ellyatt did the deed.
Especially as Florida weather is already in the 80's during the day, and he drove with the air conditioner on so he and his wife remained comfortable.
How did he do it?
First trick was to drive two segments with the cruise control at 40 miles/hr, on level ground, with few stops. Each of those segments Ellyatt achieved 50+ miles of electric range. How did that work when the EPA says the Volt gets 35 miles of electric range? As the automakers keep saying, the range figures are estimates affected by your driving habits. The same holds true in gasoline cars, where leadfooted street racers get lower miles/gallon than do the careful hypermilers. By staying below 40 miles/hr Ellyatt was able to drive more efficiently, use less energy, and get a longer electric range per charge.
One of those 50+ mile segments lasted 51.3 miles, and the car had 7 miles of range left. Ellyatt says his next goal is to see just how far one can go on a single charge, and believes the car can go over 60 electric miles. Yes, 60 electric miles on a car rated for 35 electric miles.
That covered a bit over 100 miles of the 190 total miles, so what about the rest, a bit less than 90 miles? That distance can be covered by 3 full recharging sessions which would give 105 miles of driving range by the EPA rating of the car. However, Ellyatt reports that he relied on "opportunity charges" and purposely did not fully recharge the car during the day.
Avoiding a full recharge is another trick. If you watch the charging rate, in kilowatts, throughout a charging session, during the last part the power level drops very low. What's happening is the battery management system is keeping the charger at a low setting, to avoid overcharging, while at the same time balancing the battery pack to ensure each battery cell is fully charged. In typical charging usage this is required because a balanced battery pack is a happy battery pack. However, it is not necessary to fully recharge the pack on every charge session.
Because Ellyatt's goal was to achieve maximum range, going for partial recharges was a more efficient use of time. The low charge rate at the tail end of the charging session does not add much power (range) to the battery pack. Range is determined by the kilowatt-hours in the battery pack, and by the balancing phase most of the kilowatt-hours have been put into the pack. Stopping the recharge early means the time spent with the car plugged in is during the phase where a lot of miles is being put into the pack.
This would entail driving a few miles, stopping at a recharging station, pluging in to start a charging session, stopping the charging session before it's finished, and repeating this throughout the day. The 3.3 kilowatt charger on-board the Chevy Volt provides about 12 miles of driving range per hour of charging.