Technical Article

Understanding Electric Vehicle Charging Technology

March 28, 2023 by Rakesh Kumar

The electric vehicle market's adoption is aided by the development of charging infrastructure. This article provides an overview of the charging technologies available for electric vehicles.

The primary cause of environmental pollution, which worsens air quality and contributes to global warming by releasing harmful air pollutants (such as sulfur dioxide, nitrogen oxides, carbon monoxide, etc.), is the growing number of fossil fuel-powered vehicles, such as motorcycles, cars, trucks, buses, etc. Hazardous gases harm practically every organ system in the human body and threaten the environment. Because of these serious problems, there is a critical need for vehicles that are safer, cleaner, and more efficient, like battery electric vehicles (BEVs).


Wired and Wireless Charging 

Wired and wireless charging are the two charging methods for battery electric vehicles. Due to their promising characteristics, like low pollution, no greenhouse gas emissions, and high efficiency, EVs have increasingly gained attention over the past few decades. Recent studies have shown significant and positive improvements in the use of EVs. Lower fuel costs and improved energy efficiency have increased EV market penetration.

BEVs satisfy the basic requirements for environmentally friendly transportation sources, with improved fuel economy and decreased emissions. For instance, the market share of BEVs has increased significantly since 2014. The effectiveness and cost of these specific BEVs are influenced considerably by the batteries and related charging technologies. To continue their growth rates, businesses are investing more heavily in their research into BEV charging systems.


Electric Vehicle Charging Technology

Due to their potential achievements, BEVs are currently gaining more and more attention every day. Further developing their charging systems has proven difficult due to numerous considerations, including an optimal structural design with fewer components, safety precautions, high efficiency, fast charging, etc. Two different charging technologies can be distinguished from one another: wired charging (contact charging) and wireless charging (contactless charging).


Wired Charging Technologies

First, wired charging methods, which may be further broken down into AC and DC charging technologies, require a direct cable connection between the EV and the charging equipment to achieve charging. Figure 1 shows the overall charging technologies available for BEVs.


Figure 1. Overall charging system for BEVs using wired/wireless. Image used courtesy of IEEE Access


AC Charging

By using AC charging technologies, EV batteries are not charged directly; rather, the battery is charged by the onboard charger (OBC) that supplies the battery. These technologies add weight to the entire system because the conversion unit, which converts AC into DC, is housed inside the vehicle. They are frequently charged using either single-phase (1ϕ ) onboard slow charging or three-phase (3ϕ ) onboard fast charging systems.

Most of the time, the AC charging method sends power to the OBC, which turns the AC into regulated DC. Not only do OBCs take over the conversion from AC to DC, but they also improve the quality of the regulated current (fewer ripples, less switching loss, and less electromagnetic interference, or EMI). AC charging technologies are also mostly used in BEVs, with power levels and charging times of less than 20 kW and 2–6 h, respectively.


DC Charging

In contrast to AC charging methods, DC charging technologies can directly charge the battery, providing fast charging capability. Off-board fast charging and off-board rapid charging systems are two more subgroups of DC charging technologies. Because the conversion unit is distinct from the vehicle, such technologies can result in a reduction in the overall size and weight of the driving system in the car.

DC charging methods have been developed that can charge a high-capacity battery in less than an hour. Figure 2 shows how the system for charging BEVs with wired and wireless charging works. As shown in this diagram, the OBC is mostly built into the BEV. It comprises a full-bridge rectifier, a power factor correction circuit, and a chopper like a dual-active bridge, which indirectly charges the battery. Unlike the onboard charger, the off-board charger is installed outside of the BEV at a charging station and feeds the battery directly.

Installing the battery management system (BMS) is more expensive, and they do not provide the flexibility to charge the battery in multiple locations. Wired charging solutions have made some impressive and encouraging advancements, but one of their main limitations is that they are rigid, which restricts where they may charge. The BMS should also be considered regarding the demands for safety and dependability, both of which are challenging.


Figure 2. Overall charging system for BEVs using wired/wireless charging technologies. Image used courtesy of IEEE Access


Wireless Charging Technologies

On the other hand, the problems with wired charging technologies, such as the need for charging cables, maintenance, and safety concerns, have led to research into wireless charging technologies. In these kinds of technologies, the BEV has to park above the charging system to get the high-frequency charging current. Wireless charging technologies can be divided into three categories: near-field, medium, and far-field.


Near-field Charging and Medium-field Charging

Near-field charging includes inductive charging, magnetic-resonant charging, and capacitive charging. Medium-field charging includes magnetic-gear charging. The first two charging methods, near-field and medium-field charging, also known as mechanical charging, are the most common and used today for BEVs. Each day, more people are requesting wireless charging technology.

EV batteries do not need to be directly connected to wireless charging methods, which are less expensive than cable charging technologies. Instead, by converting the grid-frequency AC (50/60 Hz) to a high-frequency AC (up to 600 kHz), which is then delivered via a transmitter pad and received by a receiver pad attached to the BEV being charged, it is possible to wirelessly charge the batteries.


Far-field Charging

Far-field charging technologies, like laser charging, microwave charging, and radio wave charging, are still the subject of a lot of research and are expected to be the future of wireless charging technologies. Far-field charging methods are considered the best option for EV charging in the future. Nevertheless, if the connection between the transmitter and the receiver is lost, one of the biggest problems of wireless charging technologies is that they can quickly become out of control.


Takeaways of Electric Vehicle Charging Technology

This article has discussed the charging technologies of battery electric vehicles. Some of the takeaways follow.

  • Modern existence is threatened by global warming and air pollution due to increased emissions from most cars. These major issues necessitate safer, cleaner, and more efficient vehicles like battery electric automobiles.
  • Proper charging technology is a critical component in the development of electric vehicles. Wired and wireless charging are the two ways battery electric vehicles can be charged.
  • In the wired charging technique, direct cable connections between the electric vehicle and the charging apparatus are provided, which may be further separated into AC and DC charging technologies.
  • AC batteries are frequently charged using both single-phase (1ϕ) onboard slow charging and three-phase (3ϕ) onboard fast charging.
  • Through the use of DC charging techniques, batteries can be charged quickly. Two further subcategories of DC charging technologies are off-board fast charging and off-board rapid charging systems.
  • Wireless charging requires parking the car over the charging equipment to receive high-frequency charging current. Wireless charging has three categories: Near-field, medium-field, and far-field charging.
  • Near-field charging includes inductive charging, magnetic-resonant charging, and capacitive charging, and medium-field charging includes magnetic-gear charging, both of which are the most frequent charging methods.
  • The future of wireless charging is predicted to include far-field charging technologies like laser, microwave, and radio wave charging, which are still the focus of extensive research.


This post is based on an IEEE Access research article.

Featured image used courtesy of Adobe Stock