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What’s Under the Hood? EV Chargers: A Tale of Standards and Many Connectors

Oct 12, 2022
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Rapidly growing electric vehicle (EV) sales are fueling growth in charging infrastructure and expected to be valued at $40 billion per year by 2030 across all power levels. This will offer tremendous opportunities for companies along the EV charging value chain.1

In this chapter of Wolfspeed’s What’s Under the Hood series we introduce various standard charging power levels and describe the variety of EV charger plugs used globally. Finally, we discuss the types and standards of communication between vehicle and charger, and charger and grid.

Although the most common type of EV charger is one that plugs into a standard wall outlet at home, there are standards for different AC power levels and DC fast charging (Figure 1). The first two charging power levels are based on AC supply and use the EV’s onboard charger (OBC) to convert AC power from the conventional AC grid to DC.

Each level typically uses plugs and communication pins and protocols governed by international (IEC and ISO) or national standards, or Tesla.

Figure 1: The three levels of charging standard in the U.S.

Level 1 Charging

Level 1 equipment utilizes single-phase 120 V AC, typically from a standard household outlet that is rated for a maximum of 15 A with 12 A derating with circuit breakers. This limits the maximum available power to 1.4 kW, but dedicated 20 A outlets can take that up to 2.4 kW.

Level 1 is used mainly in North America, because the lowest domestic mains voltage in the rest of the world is about twice that level. This level of charging delivers a driving range of about 4-6 miles (6.4-9.7 km) per hour, taking 40-50 hours to fully charge from empty.2,3

Level 2 Charging

AC Level 2 equipment offers charging with household 240 V in Europe and other parts of the world. At 3.3 kW to 22 kW, it can deliver about12-54 miles (19.3-86.9 km) per hour. From empty to a fully charged EV, Level 2 charging takes anywhere from 4-10 hours.2

The specification provides for up to 80 A (19.2 kW maximum) on a single phase, but most outlets are rated 30-40 A. At 40 A, the available maximum power is only 9.6 kW. However, with special multi-phase circuits, such as those provided at commercial U.S. charging locations, up to 22 kW can be achieved. More than 80% of the public EV supply equipment (EVSE) in the U.S. is estimated to be Level 2.3

Level 3 Charging

At Level 3, also called DC Level 2 or DC Fast Charging (DCFC), EVSE can charge an EV from empty to 80% in just 15-45 minutes, typically adding anywhere from 100 to more than 200 miles (160.9-321.8 km) of driving range in one hour.

Utilizing three-phase AC-to-HVDC (vehicle battery voltage), these chargers require dedicated infrastructure to deliver 50-300+ kW, which is particularly useful for medium- to heavy-duty EVs like vans and trucks, as well as passenger EVs on long road trips.

About 15% of public EVSE ports in the U.S. are estimated to be able to support DC fast chargers.3

Standards and Plugs

The EV industry has not agreed on a single AC or DC connector, and there are significantly more plugs (connectors) than power levels for EV charging. Depending on the EV brand and country, the connector varies in shape, size, and pin configuration.

Illustrated examples of the EV charger connectors available around the world.
Figure 2: A variety of EV charger connectors has evolved to address a large market.

In general, all connectors use two or more large pins for power—L1, L2, L3 for AC phase lines, N for neutral, AUX for auxiliary, and PE or GND for protective earth or ground—and several smaller pins for communication control pilot (CP), proximity pilot (PP), and controller area network (CAN), as well as proprietary pins (Figure 2).

SAE J1772: The J1772—J-plug or the Yazaki connector—is specified in IEC 62196-2 as an implementation of the Type 1 connector for charging with single-phase AC. Although specified for both Levels 1 and 2, it is mostly used in the U.S. and Japan. Tesla plugs can use an adapter to charge using the J-plug.

The Type 1 connector has a round housing with five pins; there are two AC power pins, an earth wire, and two signal pins: PP and CP.

Mennekes: Defined as the Type 2 connector by IEC, it is standard in Europe for Level 2 charging. Tesla uses the Type 2 connector in Europe for AC and DC charging. The connector has five power pins for neutral and three AC line phases and earth, allowing use for both single- and three-phase charging. It also has two small signal pins for CP and PP.

GB/T: This is short for guojia biaozhun/tuijian, meaning it is a recommended (but not mandatory) national standard. China’s GB/T 20234-2015 standard adopts an AC connector that is similar to but not compatible with the Type 2 Mennekes connector. The plug allows AC charging at 8 kW or 27.7 kW with currents 10/16/32 A at 250 V or 16/32/64 A at 440 V.

For DC charging, GB/T has a different plug that is unique in its ability to simultaneously charge both the low-voltage auxiliary battery and the high-voltage traction battery in the EV.

CCS: The combined charging system (CCS) standard unites AC and DC charging into a single connector that has been widely adopted in the U.S., the E.U., and South Korea. In the U.S., CCS 1 places two additional DC power pins below the AC J1772 configuration. The E.U. uses CCS 2 that similarly combines the AC Type 2 connector with the DC power pins. Also called combo, the CCS connector complies with IEC 62196-1, 62196-2, and 62196-3 standards.

CHAdeMO: This standard for DC fast-charging developed by a consortium of Japanese companies, including Toyota, Nissan, and Mitsubishi, has been published as IEC 61851-23, 61851-24, and 62196-3 as well as IEEE 2030.1.1TM-2015. However, in the U.S. only Nissan and Mitsubishi sell EVs with this connector.

CHAdeMO uses “Type 4” EV connectors that have three power pins and six signal pins.

Tesla Connector: This proprietary plug supports Levels 1 through 3 of charging conditions. The plug, the only option available with Tesla cars in the U.S., uses three power pins (including earth) and two signal pins. Tesla plugs are unique in using the same connector and pins for both AC and DC charging.

In Europe, however, Tesla supplies a Type 2 cable with all models and a CCS 2 adapter with Model X and S (Model 3 uses CCS 2) and separately sells a CHAdeMO adapter.4

Communication Protocols

The way the vehicle, charger, and grid talk to each other is standardized and focused on two main communication flows—between vehicle and charger, and between charger and grid. The information that needs to be conveyed by the signal pins in the various connectors discussed above is guided by the standards IEC 61851, ISO 15118, DIN 70121, and VDV 261, which define multiple levels of functionality. Each function uses a different communication method and provides different levels of features and status support (Figure 3).

Figure 3: The IEC 61851 standard defines the functionality of the control and proximity pilots from low through high levels of charger-vehicle communication.

Low-level communication (IEC 61851): It provides limited functionality related to charging state and maximum current and uses the proximity pilot pin to determine the status.

Medium-level communication (IEC 61851-1): It uses the control pilot and pulse-width modulated (PWM) signals that alternate between two defined levels. The EVSE specifies the maximum charging current for the EV via the duty cycle. The IEC 61851-1 standard defines the applicable duty cycle values. While the functionality is similar to that at the low level, high-level communication can be forced.

High-level communication (IEC 61851-1): A requirement for DC charging, this level uses IPv6-based protocol structure and power line communication (PLC) technology over dedicated pins, such as CP and PE in CCS. Two common protocols are ISO 15118-3- and DIN 70121-compliant signal-level attenuation characterization (SLAC) and CAN, with the latter used by DC GB/T and DC CHAdeMO.

Charger to grid: The charger-to-grid communication happens over ethernet (or wirelessly through cell networks) using the open charge point protocol (OCPP), an application protocol that allows EVSE to talk through a central management system. The vision of OCPP is to make any EV charger work with any charger management software, and possibly support value added services.

Conclusion

EV charging infrastructure landscape currently has a large number of connectors and siloed service providers, which limits “charger roaming” or the ability to use any charging station closest to the EV owner. But this last challenge to widespread and rapid EV adoption is already being addressed through industry effort. For instance, more than 50% of EVs in the U.S. have now adopted the CCS standard5, and Tesla, which prohibits U.S. non-Tesla EVs from its chargers using software validation, has opened access to its vast charging infrastructure in Europe.6

As this market continues to evolve and place new requirements on designers, keep abreast of the latest application trends and solutions at Wolfspeed’s Power Knowledge Center.


References

  1. IDTechEx, Charging Infrastructure for Electric Vehicles 2020-2030 (https://www.idtechex.com/en/research-report/charging-infrastructure-for-electric-vehicles-2020-2030/729)
  2. U.S. Department of Energy, Developing Infrastructure to Charge Electric Vehicles (https://afdc.energy.gov/fuels/electricity_infrastructure.html)
  3. U.S. Department of Transportation (https://www.transportation.gov/rural/ev/toolkit/ev-basics/charging-speeds)
  4. Tesla E.U., Charging Connectors (https://www.tesla.com/en_EU/support/charging-connectors)
  5. Abby Brown, et al., NREL, ICF Inc., Electric Vehicle Charging Infrastructure Trends from the Alternative Fueling Station Locator: Fourth Quarter 2021 (https://afdc.energy.gov/files/u/publication/electric_vehicle_charging_infrastructure_trends_fourth_quarter_2021.pdf)
  6. Tesla, Non-Tesla Supercharger Pilot (https://www.tesla.com/en_EU/support/non-tesla-supercharging)
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