What “E-Mobility” Means to the Electrical EngineerMay 04, 2020 by Nicholas St. John
"E-mobility" may seem like a mega-trend buzz word in the industry. But the circuit-level designs that drive this term (especially those involving EV batteries and charging technology) directly affect engineers.
In recent years, the term e-mobility has become yet another consumer electronics buzz word that, at first glance, seems to hold little weight for the electrical engineer.
But a definition of the term according to Gartner proves that this isn't the case. E-mobility refers to a system of "using electric powertrain technologies, in-vehicle information, and communication technologies and connected infrastructures to enable the electric propulsion of vehicles and fleets.”
Comparison of hybrid and all-electric vehicles. Image used courtesy of Infineon
It's in this definition that we can see how the big-picture trend of e-mobility integrally affects the projects handed to designers in the automotive sector.
The systems that make up these vehicles, as well as the systems in charging stations, will require both innovation and increased production from EEs. So, what are the specifics that go into "e-mobility?"
E-mobility and the Growing Demand for EVs
According to a study conducted by the Edison Electric Institute, the number of electric vehicles on the road in the United States from 2011 through 2019 rose on an exponential scale.
Electric vehicles on the road in the US from 2011–2019. Image used courtesy of the Edison Electric Institute, Inside EVs, and Hybrid Cars
But this demand for EVs isn't isolated to the United States. A McKinsey & Company report on the demands of an EV charging infrastructure reveals that on a worldwide level, we are seeing increases in EV sales as well, especially in the EU and China. We've even discussed how the UK plans to ban diesel and petrol car sales altogether by 2035 in favor of electric vehicles.
While the push for EVs is not a surprise, what with global green technology initiatives, there are many obstacles to overcome—beyond the effort of running a vehicle on a battery alone. Electrical engineers, along with civil engineers, city planners, and other professionals, will need to step up to establish charging stations, infrastructure, and manufacturing for EVs in mass production.
There are a host of design considerations for electrical engineers in the e-mobility sphere, some of which include control systems, battery systems, battery memory, charging devices, battery management, and electronic accessories (power windows, power steering, etc.). But for the sake of simplicity, we'll discuss the two most pressing subcategories in this discussion: batteries and charging stations.
The Challenges of EV Batteries
One of the biggest design concerns with EVs is battery capabilities. Isidor Buchmann, the founder of Cadex Electronics, points out the key comparisons among common EVs, including energy consumption and cost per km/mile.
Comparisons of the estimated energy consumption and cost per km/ mile of common EVs. Image used courtesy of Isidor Buchmann
As we can see, the maximum range according to this table is 310 miles, comparable to my 2004 Chevrolet Impala’s capability on the highway. While that range is acceptable for most drivers, we see that the average range is only 118 miles. This mileage may work for the average commuter, but with current infrastructure lacking enough EV charging stations, these vehicles are not a great option for road trips, long commutes, and traffic jams.
The solution seems simple—make EVs with a higher range—but this task is not as cut and dry. According to Forbes contributor Tony Posawatz, extending the range of EVs would require manufacturers to increase the battery size, which would make the entire vehicle much more expensive and introduce other design challenges for the engineer.
The Basic Types of Charging
Meanwhile, charging stations are another issue that designers must face. EVs with smaller batteries currently rely on quick-charging stations, which are expensive and require a large amount of power. An EV capable of longer ranges can fare well with slower charging stations for day-to-day travel and use fast charging for longer trips (i.e. on the interstates).
According to a guide on EVs from the University of Tennessee Chattanooga, there are three types of EV battery chargers that vary the rate in which they charge.
- Constant voltage: The battery charges under a constant voltage and flow. When the battery is fully discharged, the charger blasts its highest current. Then, when it is nearly charged, the charger steps down to a low current. This type of charge is both simple to implement and inexpensive.
Constant voltage. Image used courtesy of the University of Tennessee Chattanooga
- Combination of constant current/constant voltage: An EV's charge cycle begins with a high constant current. Once the voltage reaches an established limit, it switches into constant voltage control. This type of charging boosts battery performance and extends battery life because it reduces heat during the charging process.
Combination constant current/constant voltage. Image used courtesy of the University of Tennessee Chattanooga
- Pulse charging: Pulse charging "pulses" voltage, eliminating the need for constant current or voltage. Pulse charging surges a series of high current and voltage pulses until the battery voltage meets a certain threshold. This type of charging dramatically reduces heat and charge time while saving energy.
Pulse charging waveform. Image used courtesy of the University of Tennessee Chattanooga
Improving an E-Mobility Ecosystem
All of these design decisions that will affect engineers—big batteries, small batteries, fast charging, or slow charging stations. Keysight mentions the several ways that engineers might be involved in the e-mobility ecosystem: improving battery performance and electric drivetrains while learning to design efficient charging stations and better power conversion.
For the EV itself, designers can look forward to more innovative projects involving short-, mid-, and long-distance battery packs that play nicely with slow, fast, or otherwise-specialized charging systems. Charging stations must be able to perform any type of charge (constant voltage, a combination of constant voltage/current, and pulse charging) an EV will require.
Charging station. Image used courtesy of Infineon
For these reasons, designers of EVs, batteries, and electrical infrastructure must be mindful of the network of technologies under the umbrella of "e-mobility" instead of focusing on isolated challenges in a single device.
Get Into the Nitty Gritty of E-Mobility
For more information about EV battery systems and charging standards, check out some of our past articles that cut to the heart of e-mobility.
Have you worked in an "e-mobility" sector? What are the day-to-day design challenges you face? How do you overcome those challenges? Share your experiences in the comments below.