EV Rangepart 2

EV-201b

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)

EV RangeRange is the distance you can travel when the EV battery is fully charged.Range is affected bythe battery capacityVehicle parametersspeeddesignDriving conditions

Source: https://sites.google.com/site/evehics/saving-the-environment/data-table

In the first part of this EVU mini-course, you learned that>> Range is the distance you can travel when the EV battery is fully charged.

>> We discussed the overall factors that affect range>> battery capacity>> Vehicle parameters such as >> speed>> and vehicle design

>>and the influence of Driving conditions

In the second part of this mini-course, well discuss vehicle parameters in a bit more detail and delve into the affect of driving conditions on range.

Vehicle Characteristics

Drag Area

As weve discussed, design is a pivotal factor in building an EV with good range. And a major design objective is to reduce drag.

>> Drag area is the front facing area that is impacted by airflow as the vehicle moves forward, measured in sq feet or sq. meters.

>> To illustrate how a few the most popular EVs compare to one another, heres a histogram for Drag Area (represented in yellow) and the drag coefficient (represented in blue). To make the chart easier to read at a glance, weve multiplied the drag coefficient by 10

Its important to note two things: drag area is not the only parameter that affects aerodynamic drag, and hundredths matter when the drag coefficient is considered.

Pause your video for just a moment and examine the chart to get a feel for how the EVs compare.

Looks can be deceiving Small cars dont necessarily have the lowest drag areaFast cars dont necessarily have the lowest CdConsider the Tesla Model Sbig car, but lowest drag area for an EVbig car but lowest coefficient of drag for an EVTesla Model S, Cd = 0.24Corvette ZR-1, Cd = 0.28Bugatti Veyron, Cd = 0.36

Looks can be deceiving when drag is considered.

>> Small cars dont necessarily have the lowest drag area>> Fast cars dont necessarily have the lowest drag coefficient

Remember, for drag coefficient, the lower the number, the slipperier the car, and for EVs, the better the range for a given battery capacity

>> Consider the Tesla Model S>> its a big car, but it has the lowest drag area of any production EV to date>> it also has the lowest coefficient of drag for any production EV to date

>> The Tesla Model S has an a drag coefficient of 0.24

>> Thats significantly lower that the Corvette ZR-1 with a drag coefficient of 0.28 >> and shockingly, much, much lower than the $2.1 million sports carthe Bughatti Veyronwith a drag coefficient of 0.36.

So to get good range, an EV must be slippery.

But to get a feel for drag forces, we have to descend into some math for just a moment

The Effects of Drag

Cd drag coefficient (the lower, the better)A drag area (the lower, the better)Rho air density (relatively low variability)V velocity (how you drive in specific situations)

Those of you who are math challenged probably panicked just a little when this equation appeared, but its important for your understanding of EV range. At the end of the day, range is dominated by the laws of physics and aerodynamics. But you dont need to be a science and math major to get this.

It really is pretty simple.

As I mentioned earlier, Your battery must provide the energy necessary to generate the force required to push your EV through the air. The more force required over time, the less range youll get out of your battery.

From the equation:

>> Cd drag coefficient (the lower, the better)>> A drag area (the lower, the better)>> Rho air density which has relatively low variability>> V velocity, that is, how fast you drive; note that force is affects as the square of the velocity

The goal of every automotive designer is to keep the force, FD, as low as possible.

Driving ConditionsThe prevailing windThe lay of the landThe temperatureRoof racks or towing

But there are other environmental factors that also affect range. Most of these are out of your control, but they do matter.

>> The direction and velocity of the wind can have an immediate affect on range. Thats simply common sense. If youre driving into a strong wind, more force is required, and range is affected

>> The same goes for the terrain youre driving over. If its hilly or mountainous, range will be affected, possibly as much as 30 percent in extreme situations.

>> Temperature effects are more subtle, but very cold weather can have a significant affect on the battery, and therefore, on range. In fact, it can reduce range by as much as 20 30 %

>> Finally, as I mentioned in part 1 of this mini-course, anything (like a roof or bicycle rack) that you attach to the exterior of the EV can have an affect on rangeand generally that affect is negative.

Maximizing Rangeplugincars.com provides a few additional suggestionsCheck your tire pressureLook for travel routes with small gradients and few interectionsSchedule your charging to stop just before you driveGive yourself more time

>> In addition to the topics weve discussed, plugincars.com offers these suggestions for improving the range of your EV:

>> Check your tire pressurerolling resistance can affect range>> Look for travel routes with small gradients and few intersections>> Schedule your charging to stop just before you begin drivingthis reduces the likelihood of any small loses that may occur as the car sits idle with a full charge >> Give yourself more time, resulting in relaxed driving and more effective use of regen

PHEV RangeDifferent PHEV architectures and different modes of operationto determine all electric range (AER), a PHEV must be used in charge depleting mode.in such cases AER for PHEVs is quite lowIn balanced or charge sustaining model, the range of a PHEV combines the ICE and electric motor.

An earlier EVU minicourse we discussed various >> PHEV architectures and noted different operational modes for PHEVs.

>> to determine the all electric range a PHEV must be used in charge depleting mode.That means that the PHEV is running solely off the battery with no ICE assist.>> in such cases the all electric range for PHEVs is quite lowHowever, >> In balanced mode or charge sustaining model, the range of a PHEV combines the ICE and electric motor and can easily exceed 300 miles.

SummaryRange is the distance you can travel on a full batteryVehicle parameters and environmental conditions affect rangeVehicle speed and aerodynamic drag have a significant roleBattery capacity is the dominant issue

Lets summarize what weve discussed.

>> Range is the distance you can travel on a full battery>> Vehicle parameters and environmental conditions affect range>> Vehicle speed and aerodynamic drag play a significant role>> But battery capacity is a dominant issue

Now that you understand range, it time to consider range anxiety, and well do that in the next EVU mini-course in this sequence.

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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