For the Volt, How?s Life After 40 (Miles)?
SITTING behind the wheel of a 2011 Chevrolet Volt prototype on
Wednesday, I found myself confronting what may be the greatest fear that
future owners of electric vehicles will face: a battery-charge indicator
showing just a few miles of remaining range.
If I were out on a desolate Interstate in a vehicle powered solely by
batteries, I?d be praying to the god of electrons for a place to pull
off and plug in a charging cord. But my drive is at General Motors?
proving grounds here, and I?m about to experience what the Volt?s
vehicle line director (and my passenger), Tony Posawatz, says is the
car?s trump card: a gasoline-powered generator under the hood.
Like other reporters, I had already driven Volt prototypes in the
battery-powered mode, and they were predictably smooth and silent. But
for eventual Volt owners, a crucial ? and so far unanswered ? question
is how the car will perform when the battery?s charge is depleted and
all electricity is provided by an onboard generator, driven by a
gasoline engine, that has no mechanical connection to the wheels.
Will it be a slug? How annoying will the noise of the generator?s engine
be in an otherwise mute car?
G.M. engineers say that a fully charged Volt is capable of 40 miles of
purely electric driving before the computer calls for the generator,
which has an output of 53 kilowatts (about 71 horsepower), to start and
sustain the battery?s minimum charge level ? the ?extended range?
So what is life after 40 like in the Volt?
It takes a few laps of Milford?s twisty, undulating 3.7-mile road course
to deplete the remaining eight miles of battery charge. With the
dashboard icon signaling my final mile of range, I point the Volt toward
a hill and wait for the sound and feel of the generator engine?s four
pistons to chime in.
But I completely miss it; the engine?s initial engagement is inaudible
and seamless. I?m impressed. G.M. had not previously made test drives of
the Volt in its extended-range mode available to reporters, but I can
see that in this development car, at least, the engineers got it right.
I push the accelerator and the engine sound does not change; the ?gas
pedal? controls only the flow of battery power to the electric drive
motor. The pedal has no connection to the generator, which is programmed
to run at constant, preset speeds. This characteristic will take some
getting used to by a public accustomed to vroom-vroom feedback.
A few hundred yards later, as we snake through the track?s infield
section, the engine r.p.m. rises sharply. The accompanying mechanical
roar reminds me of a missed shift in a manual-transmission car. For a
moment the sound is disconcerting; without a tachometer, I guess that it
peaked around 3,000 r.p.m.
I asked what was going on.
?The system sensed that it?s dipped below its state of charge and is
trying to recover quickly,? Mr. Posawatz said. ?The charge-sustaining
mode is clearly not where we want it to be yet.?
Immediately the engine sound disappeared, although it was still spinning
the generator. A few times later in our test, the generator behaved in
similar fashion ? too loud and too unruly for production ? but there is
time for the programmers to find solutions. Volt engineers are revising
the car?s control software, which will have the effect of ?feathering?
the transition from the nearly silent all-electric mode to the
charge-sustaining mode, when the generator will be operating.
?We?re designing a software set of rules, which will just require more
seat time for the engineers to finish,? Mr. Posawatz said. ?We have nine
months to work this out.?
The sound of the generator running at steady highway speeds is something
Volt owners, and others who appreciate the flexibility and efficiency of
this type of hybrid system, may have to accept.
Unlike many electrics, including the Tesla Roadster, the Volt?s electric
drive has no whine. The car feels solid and planted on the road.
Clicking the Sport button on the dashboard releases a bit more oomph
than when in Normal mode; in terms of efficiency, there isn?t much
difference between the two except at peak power.
The Low mode? Chevrolet plans a flashier name for it by next fall ? is
unique in the electric-car world, and a useful feature. While coasting,
it applies electric motor braking, then smoothly blends in the regular
Even beyond the regenerative function, Low mode offers one-pedal driving
in slow speed, stop-and-go, and downhill environments. The regenerative
braking, whether applied through the Volt?s foot pedal or by pulling the
shift lever down into Low mode, is both progressive and predictable.
This is in stark contrast to the harsh, abrupt regenerative braking
delivered by BMW?s all-electric Mini-E, for example.
There is minimal body lean in the tight corners. The
low-rolling-resistance Goodyear tires created specifically for the Volt
provide excellent grip.
Throughout my test, the prototype behaves admirably. At its current
state of development, the Volt is an extremely refined vehicle.