Electric vehicle technology has advanced rapidly
since its introduction, and today there are
many plug-in hybrid and battery electric vehicle
options available on the market.
But how, exactly, do electric vehicles work
and what are their advantages?
Let’s start by considering the legacy vehicle
technology: the internal combustion engine, or ICE.
This vehicle is propelled by a combustion
engine that can only be fueled by gasoline.
The technology is conventional, well-established,
and reliable, but it consumes large amounts
of gasoline—which can be costly in many ways.
Enter the electric vehicle drivetrain.
Unlike internal combustion technology—which uses combustion and pressure to propel a vehicle—electric
vehicles, or EVs, are propelled by electromagnetism.
These vehicles use electricity, typically
stored in a battery, to power an electric motor.
EV technology is used in hybrid electric vehicles,
or HEVs; plug-in hybrid electric vehicles,
or PHEVs; and battery electric vehicles, or BEVs.
The hybrid electric vehicle was the first
EV technology to reach the modern vehicle market.
HEVs, such as the Toyota Prius and Lexus CT-200-H,
are popular because of their increased fuel efficiency.
These vehicles combine an internal combustion
engine and an electric motor with a small
battery for storing electricity.
Although an HEV is only fueled by gasoline, the vehicle’s battery is also used to power the electric motor.
The electricity stored in the battery primarily comes from recapturing energy through regenerative braking.
This use of recaptured energy is one of the reasons an HEV is more fuel-efficient than a typical ICE vehicle.
Like the original hybrid, the plug-in hybrid
electric vehicle is propelled by an internal
combustion engine and an electric motor.
However, the PHEV has a much larger battery
pack that can be charged using electric vehicle
supply equipment, or EVSE.
This enables the vehicle to operate in all-electric
mode—in which the vehicle is propelled using
only the electric motor—until the battery is mostly depleted.
At this point, the vehicle operates in hybrid
mode until the fuel in the gas tank is depleted.
Increasing the battery size and running the
vehicle on electricity reduces tailpipe emissions
and increases the vehicle’s fuel- and energy-efficiency.
The final type of electric vehicle technology
is the battery electric vehicle.
This vehicle has no internal combustion engine
and is powered only by the battery and electric motor.
BEVs don’t use gasoline and are only charged by EVSE.
A BEV has the largest battery of all the vehicle types.
It’s also the most energy-efficient and
produces zero tailpipe emissions.
Because each vehicle type incorporates different
technologies, the range these vehicles can
travel differs as well.
ICE vehicles—fueled only on gasoline—typically
can travel 350 to 450 miles on a full tank of gas.
Hybrid electric vehicles are more efficient
in their use of gasoline and typically can
travel 550 to 700 miles.
Although they do have a battery and electric
motor, this battery is only fueled during
a typical drive cycle and is not a primary source of propulsion.
However, due to regenerative braking, this
small battery is the primary reason for the
hybrid’s increased fuel efficiency and range.
The larger battery in a plug-in hybrid electric
vehicle enables the vehicle to operate in
all-electric mode, typically traveling 20
to 40 miles just on electricity.
PHEVs are designed to support average daily
commutes and easy overnight recharging using
a standard outlet.
After most of the energy in the battery is
depleted, the vehicle can operate in hybrid
mode for longer distances, running off gasoline
and using a small portion of the battery to
support the electric drivetrain, for a full
vehicle range of 450 to 550 miles.
Finally, a battery-electric vehicle has the
simplest and most efficient drivetrain with
a typical battery range of 150 to 300 miles.
BEVs can be charged overnight using standard
residential Level 2 EVSE.
The most noticeable difference between driving
an electric vehicle and a conventional ICE vehicle
is regenerative braking.
Regenerative braking means the electric motor
is operated in reverse, thereby applying a
braking force through electromagnetism.
This recaptures some of the vehicle’s kinetic
energy by charging the battery.
Some electric vehicle models have specific
driving modes that incorporate varying levels
of regenerative braking.
Under normal driving conditions, an EV such
as the Tesla Model S engages regenerative
braking to slow the vehicle when the driver
removes their foot from the accelerator.
The “Standard” setting provides the maximum
amount of regenerative braking power—
it recaptures the most energy and reduces wear and tear on the brakes.
Alternately, the “Low” setting incorporates
a reduced regenerative braking force that
recaptures less energy but allows the vehicle
to coast farther than in the “Standard” mode.
An EV like the Tesla Model S also has specific
settings for how the braking systems operate
when the vehicle is stopped or moving at very low speeds.
The “Creep” mode is designed to replicate
the idling speed of an ICE vehicle.
It disengages regenerative braking and applies
a small amount of motor torque when stopped,
or at low speeds when the driver’s foot is off the accelerator.
This feature is most commonly used in a parking
lot when searching for a place to park.
Alternately, the “Roll” setting also disengages
regenerative braking at low speeds but does
not apply motor torque.
This allows the vehicle to roll freely, similar
to a vehicle in neutral.
Finally, the “Hold” setting continues
to engage regenerative braking until the vehicle
comes to a complete stop, which helps reduce
brake wear and produces the greatest amount
of recaptured energy.
This feature also automatically engages the
friction brakes when the vehicle is completely
stopped, holding the vehicle in place until the driver’s foot is placed on the brake or the accelerator.
In all of these braking modes, the brake pedal
is always available and operates the same
way as in a conventional vehicle under emergency braking conditions.
Regenerative braking modes vary with each
vehicle make and model.
For example, the Nissan Leaf provides three
levels of regenerative braking modes,
and the Chevrolet Bolt’s system involves depressing
paddles next to the steering wheel to maximize
regenerative braking and bring the vehicle
to a complete stop.
With two completely separate drivetrains—electric
and combustion—PHEVs can incorporate regenerative
braking and also operate under many different driving modes.
For example, the Ford Fusion has three driving modes—"Auto EV,” “EV Now,” and “EV Later”—each with specific uses.
The “Auto EV” mode incorporates an optimized
combination of battery energy and gasoline
to provide the most efficient use of both fuel sources.
This mode is ideal for travel at faster highway speeds.
The “EV Now” mode relies entirely on the
battery and electric drivetrain,
which results in zero tailpipe emissions, similar to a battery-electric vehicle.
Finally, the “EV Later” mode conserves
battery capacity for use later in a trip.
This mode is ideal for trips that combine
traveling at highway and in-town speeds.
It uses the combustion engine at highway speeds
and reserves energy for “EV Now” mode
during a later portion of the trip when the
electric drivetrain is most efficient.
All plug-in electric vehicles, including plug-in
hybrids and battery electric vehicles,
use electric vehicle supply equipment or EVSE,
to charge their batteries.
There are three common types of EVSE. The first is referred to as a Level 1 charger.
Typically, these units are portable cord sets
that run off a standard 120-volt household
outlet and provide approximately 2 to 5 miles
of range per hour of charging.
This is the most affordable type of charger, but it is limited in the daily range it can supply to a vehicle.
Therefore, this application is most common
for PHEVs with smaller batteries,
or for BEV drivers with a short daily commute to work.
Level 2 chargers provide more energy per hour
and run off 208 or 240 volts.
These chargers are more expensive and are
typically installed as permanent pedestal-style
or wall-mounted units.
They provide a vehicle with about 10 to 20
miles of range per hour of charging.
This is the most common application for long-range BEVs, as well as workplace and public charging stations.
Finally, a DC Fast Charger is the most expensive
type of charger, but it provides the most
energy per hour to the vehicle.
A standard DC Fast Charger can provide 60
to 80 miles of range in about 20 minutes.
These chargers are most common along highways
and are only recommended to support occasional
long-distance trips—because frequently charging
the battery at such a high power level can
lead to battery degradation.
For federal fleet vehicles, reporting energy
consumption is a requirement of doing business.
With ICE vehicles, fuel consumption is typically
reported through the fuel card provider that
records each fueling transaction.
However, electric vehicles can be charged on-site or   off-site at wall outlets, simple EVSE units,
and networked units. Although many of these charging units can record and store transactions, some of the
most-affordable EVSE may not.
Therefore, the recommended method for measuring
energy consumption—expressed in kilowatt-hours—
is through telematics.
Telematics platforms commonly capture kilowatt-hours
and display them in an online dashboard.
A fleet manager can select a custom date range
to find a vehicle’s energy consumption in
kilowatt-hours over a certain time period.
This date range can be applied to all of the
electric vehicles in a fleet, providing the
information necessary for annual federal fleet reporting.
Networked or smart-EVSE units are another
good source of energy consumption information.
These units frequently have online dashboards,
similar to telematics, that capture energy
consumption by vehicle.
These dashboards are often accessible through
smartphone applications as well.
However, if the vehicle is occasionally charged
on another network, the data from the primary
EVSE unit may be incomplete.
In this case, drivers should try to collect
information from off-site charging stations
to supplement the data from their primary EVSE unit.
The vehicles themselves also often display
energy consumption or vehicle efficiency
on their physical dashboard.
Some vehicle models show lifetime energy consumption, so federal fleet managers will need to check
the kilowatt-hours consumed annually to complete
their FAST reports.
However, if the vehicle displays the lifetime
efficiency in miles per kilowatt-hour, fleet managers
will need to divide the annual vehicle
miles traveled by the vehicle efficiency to
determine annual energy consumed.
If all else fails, the U.S. Department of
Energy’s Federal Energy Management Program
has a simple way to estimate vehicle energy consumption: Take the vehicle’s annual mileage
reading and multiply it by the vehicle’s fuel economy, listed in kilowatt-hours per mile on Fueleconomy.gov.
