Electronic design aspects of electric vehicle charging equipment 

In this exclusive guest article for EVreporter, Mr Suresh Kamath, Managing Director at Avnet India, discusses the various electronic design aspects for electric vehicle (EV) charging equipment.

An electronic vehicle charging station is the critical cog in the smooth adoption, growth and development of the EV ecosystem in India. Integral to it is the EV design of these charging stations. Many countries have developed such infrastructure to be in sync with factors like availability, quality power, grid infrastructure, usage patterns, demand and the weather.

Let’s look at the power supply.

– The power supply is critical for any EV Charger, as it determines the charging speed and efficiency. It can charge an EV faster if powerful enough, while a less powerful power supply may result in slower charging times.

– EV chargers use two main types of power supplies: AC and DC.

– Level 1 and level 2 chargers use AC power supplies, and they convert the AC power from the grid into the appropriate voltage and current needed to charge the EV’s battery. Level 3 chargers use DC power supplies.

The next important aspect in developing an EV charging design is the Charging Modes. Several types of connectors are available for EV charging, each with advantages and disadvantages.

Here are some of the most common charging modes:

• Type 1 (SAE J1772): Using this connector, you can only charge your vehicle with single-phase AC power. This connector has five pins, mainly used by North American countries and Japan, and is suitable for slow and medium-speed charging systems.

• Type 2 (IEC 62196): This connector can charge your device with AC and DC power. This connector type has seven pins, mostly used in European countries and Australia, and is suitable for fast charging up to 45KW.

• CHAdeMO: This connector is used mainly in vehicles for DC fast charging, is prevalent in Japan and can supply electricity at up to 62.5 kW of power.

• Combined Charging System (CCS): This standardised connector is becoming more prevalent in vehicles worldwide and supports charging up to 350 kW.

An electric vehicle charging station design has to address the criticality of equipment that connects an EV to a source of electricity to recharge electric cars, neighbourhood electric vehicles and plug-in hybrids.

This aspect must be comprehensive and consider the different types of chargers and charging ports.

• One is an onboard charger: It takes the incoming AC supplied via the charge port and converts it to DC Power to charge the traction battery. It also communicates with the charging equipment and monitors battery characteristics. An EV Charger outlet delivers AC power, whereas EV batteries use DC power to charge the battery. Thus, there is a need for an AC-DC conversion of AC power to DC power.

• Another piece of vital importance is Power Relay and Contactors: Globally and in India too, manufacturers have a wide current range of 50A to 350A and switching voltage up to 1800VDC, which is widely used in high-voltage control and protection systems, charging stations, large-scale photovoltaic/energy-storage inverters, and energy storage systems.

The Automotive Research Association of India (ARAI), Pune, has published standards that prescribe the specifications for performance and safety for DC charging stations for EV and hybrid electric vehicle (HEV) applications in Indian conditions. ARAI suggests some tests to be carried out with the EVSE – DC connected to a resistive load at its rated output power.

What will the test results help to determine?

According to the EV Charging design experts, such tests will help improve the charging performance and optimal power utilisation. The following methodology is adopted to achieve the desired results while conducting technical tests.

a) Fast transient bursts:

The EVSE – when  DC, powered by the AC Supply: The network (mains) shall withstand common-mode conducted disturbances to levels given in IEC 61000- 4-4/ IS 14700 ( Part 4/Set 4 ). It is generally caused by the switching of small inductive loads, relay contacts bouncing or switching of high-voltage switchgear.

The minimal requirement for doing the tests is (IEC 61000-4-4/ IS 14700 (Part 4/Set 4): 2 kV, for a time greater than 1 min and a repetition rate of the impulses of 5 kHz is recommended.

b) Voltage surges:

The EVSE – when DC, powered by the AC the supply network (mains) shall withstand voltage surges. This is generally caused by switching phenomena in the power AC Supply network, faults or lightning strokes (indirect strokes).

The minimal requirement to conduct this test: 1, 2/50 uS surges, 2 kV in common mode, 1 kV in differential mode.

c) User Interface and Security:

The EV Charging station design should give special attention to user interface and security.

It typically includes a screen, buttons, or other input devices that allow the user to input information and control the charging process. The charging station can integrate or connect the user interface to a separate device. A well-designed interface should be intuitive, easy to navigate, and provide clear and concise information about the charging process. It should also be accessible to all users, including those with disabilities or limited mobility. The most common ones include an RFID card reader, a Touchscreen and a Mobile app.

d) Integration of IoT and Connectivity:

India’s expertise in IoT (Internet of Things) and connectivity technologies can contribute to developing smart charging solutions that are remotely monitored and managed.

e) Local Partnerships and Collaborations:

India has a strong network of industries, research institutions, and government bodies that can foster collaborations that accelerate the design and deployment of EV charging solutions.

The slow chargers come within the range of 3kW-6kW power output. They are the most easily available chargers in India. These devices take around 8-12 hours to charge an EV and are best suited for 2-wheeler (2W) and 3-wheeler (3W) EVs.

Currently, the most widely used slow chargers in India are Bharat AC-001 and Bharat DC-001. The fast chargers (type-2 AC) can also charge 2W and 3W EVs, but it can be done only with the help of an adapter, which requires additional investment.

The design cost for EV charging equipment is crucial in building the design for EV charging infrastructure. I feel it can be brought down with a focussed attention to:

• Standardisation: This helps reduce the complexity of design, manufacturing, and testing, leading to cost savings.

• Simplified Design: We need to eliminate unnecessary components or features that add to the cost without significantly improving performance or user experience as per government regulations.

• Component Integration: Integrate components into a single unit to reduce the number of quantities per set and simplify assembly. This can lead to cost savings in terms of both materials and manufacturing.

• Cost-effective Components / Raw Material selection: Avoid over-spec parts, reducing unnecessary costs.

• Research and Development: Invest in research and development to innovate and discover new cost-effective technologies.

• Collaboration and Partnerships: Collaboration with the right partners will provide the required thrust for the project.

Customers are seeking sustainable design options in building EV charging infrastructure, and it is encouraging to see companies redirecting that focus to such efforts.

About the author

Suresh Kamath is the Managing Director at Avnet India – a leading electronics technology and distribution company. Suresh is well accomplished in the semiconductor industry, with almost 25 years of experience in technical sales, marketing, and business intelligence.

Avnet has global insight into how the EV charging infrastructure is developing worldwide. It serves three tiers of suppliers in the EV value chain: offering complete systems, subsystems and modules, and components. The company works with systems integrators, module manufacturers, integrated device manufacturers, cable and connector companies, and display manufacturers.

Also Read: What’s next for light EV charging standards?