EV Architecture, BEVs & PHEVs

EV-104

This course is presented as part of Evannex Universitya free, open learning environment that presents concise, video-based mini-courses for those who have interest in electric vehicles (EVs)

What is an EV?In a formal sense, an electric vehicle (EV) uses an electric motor and an electric power source to propel the vehicleBut that leaves a number of open questions:Is the power source only a battery?Can an ICE be present?If so, how do the battery, electric motor, and ICE work together?

I think it's fair to say that the popular media is sometimes confused about EV's.

In some articles I read about electric vehicles, there are factual mistakes, misinterpretations of what an EV actually is, and generalities that might apply to one class of electric vehicle architectures that don't apply to others.

So what is an EV?

>> In a formal sense, an electric vehicle uses an electric motor and an electric power source to propel the vehicle

>> But that leaves a number of open questions:>> Is the power source only a battery?>> Can an ICE be present to supplement the battery?>> If so, how do the battery, electric motor, and ICE work together?

The answers to these questions are no and yes and in a variety of ways respectively, but that doesn't tell the whole story.

EV Purists believe that an EV should never, ever include an internal combustion engine, and its an understandable point of view

But for technical and marketing reasons, the automotive world doesnt make such clear distinctions. EVs are characterized more broadly.

What Variants Exist?Battery Electric Vehicle (BEV)Plug-in Hybrid Electric Vehicle (PHEV)Series HybridParallel HybridSeries/Parallel HybridFuel Cell Electric Vehicle (FCEV)derives electric power from a hydrogen fuel cell

Lets take a look at the variants.

>> In part 1 of our discussion of EV architecture, you learned that the purest form of EV is the Battery Electric Vehicle. The BEV uses only an electric motor and rechargable battery to power the car/

But there are other architectures that are often referred to as electric vehicles.

>> Plug-in Hybrid Electric Vehicles (called PHEVs) use a combination of an electric motor, a battery and an ICE to power the vehicle.

Within the PHEV category, we have>> The Series Hybrid that uses an ICE to power a generator that charges battery, passing electricity to an electric motor that transmits power to drive wheels>> The Parallel Hybrid which uses an ICE and electric motor provide power to transmission that transmits that power to then drive wheels>> The Series/Parallel Hybrid uses a drivetrain that combines both approaches with either the ICE or the electric motor or both in service at any given time

>> Finally, theres the Fuel Cell Electric Vehicle (FCEV) that derives electric power from a hydrogen fuel cell that can transmit power directly to an electric motor or to a battery

BEVsBattery CapacitySmall capacity vehiclessometimes referred to as city cars typically have > Battery Capacity varies significantly among BEVs>> Small capacity vehiclessometimes referred to as city cars typically have > and a range > Large capacity vehiclestoday, only the Tesla Model S falls into this category>> have >60 kWh batteries and a>> and a range 200 to 300 miles

PHEVsICE eliminates range anxietyAll PHEVs use gasoline (or another fossil fuel) and electricity from the grid to operateThe real differentiating factors:How the electric motor and the ICE are used to power the carTo what extent the battery plays a role

PHEVs are electric vehicles. After all, they do use electricity and they do have a battery. But they also make use of an ICE.

>> An ICE is used because it eliminates what we call range anxiety concern about the limited capacity of the battery to provide enough vehicle range.Well discuss range anxiety in another EVU mini-course.

In any event,

>> All PHEVs use gasoline (or another fossil fuel) and electricity from the grid to operate>> The real differentiating factors are:>> How the electric motor and the ICE are used to power the car and >> To what extent the battery plays a role

Lets take a tabular look how BEVs and PHEVs operate.

Comparing the Variants

BEVPHEV-SeriesPHEV ParallelPHEVS/PFCEVBatteryyesyesyesyesyesICEnoyesyesyesnoRegenyesyesyesyesyesICE DrivenonoyesyesnoICE chargingnoyesnoyesno

Although each EV variant comes in different flavors, even within its category, it worth trying to summarize.

Each of the variants is listed across the top row of the table you see on your screen.

For each of the EV variants, this table addresses:whether a battery is present within the EV variantwhether an ICE is used as part of the architecturewhether regen is usedwhether the ICE is used to provide force to directly drive the wheelsand whether the ICE is used to charge the battery

Pause this video if youd like to take a longer look at the table, and note that for almost every cell in the matrix, its possible to find an exception.

PHEVsModes of OperationCharge-depleting modeoperates exclusively on battery powerBlended modeused when a vehicle does not have enough battery power to sustain high speedCharge-sustaining modecontrols the use of the battery the ICE, and regen to ensure that battery charge remains with a given rangeMixed-modeuses some combination of other modes

Another way to look at PHEVs is to consider their modes of operation. >> in Charge-depleting mode the vehicle operates exclusively on battery power. This mode often occurs at low speed for a PHEV.As an aside, a BEV operates solely in charge-depleting mode, regardless of its speed.

>> Blended mode is used when the vehicle does not have enough battery power to sustain high speed and must call on the ICE for help. In this mode, the battery can still be called upon to supplement the ICE, providing better overall fuel economy.

>> Charge-sustaining modecontrols the use of the battery, the ICE, and regen to ensure that battery charge remains with a given range

>> and Mixed-modeuses some combination of other modes

On any given trip, the speed of the vehicle and distance traveled will dictate the model of operation.. For example, a PHEV that travels a few miles at low speed would use charge-depleting mode, but on an interstate at higher speed, it would use blended mode instead.

Its important to understand that even within one PHEV architecture, the application of these modes of operation will vary from vehicle to vehicle.

The PHEV SystemAll make use of an ICE and incorporate the added complexity associated with an ICEICE-electric motor coordination complexityAll use gasoline or another fossil fuel All produce emissions, but can also achieve emission-free driving for short distancesAll are energy efficient

Today, PHEVs are the most common EV.

>> All make use of an ICE and incorporate the added complexity associated with ICE>> Theres also the complexity associated with coordinating the operation of two different power sourcesthe ICE and the electric motor>> All PHEVs use gasoline or another fossil fuel >> All produce emissions, but can also achieve emission-free driving for short distances>> All are energy efficient

But as battery technology continues to improve, it likely that the added complexity of the PHEV will cause the architecture to be replaced by the BEV.

Time will tell.

SummaryMany EV variants existThe BEV is the simplest and some would argue, the bestThe PHEV is implemented in a number of different waysThe FCEV represents new technology

Lets summarize what weve discussed.

>> Many EV variants exist, and some use an ICE as well as a battery>> The BEV uses only a battery, is the simplest, and some would argue, the purest form of EV>> The PHEV uses both a battery and an ICE, is implemented in a number of different architectures>> The FCEV generate electricity on-board the vehicle and represents new technology that has promise

In part 3 of our discussion of architecture, we take a look at system diagrams for each of the architectural variants.

a free study guide for all EVU mini-courses is available for download from our website For a complete list of mini-courses and the study guide, visit: www.evannex.com

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