Making Sense of Electric Vehicle Charging Options
When it comes to charging your electric vehicle there are several options to consider based on speed, convenience and cost.
In the recent article on the Wallbox acquisition of COIL, EE Power briefly reviewed the Wallbox portfolio of EV charging solutions. EV charging solutions are not all the same and within just the Wallbox portfolio there are multiple solutions with varying charge rates, price points and installation requirements. Charging platforms can be suited to long or short-distance driving, public or home use and can have vastly different installation and operational costs.
In this article, EE Power takes a closer look at the different types of EV charging stations, their capabilities and use cases.
EV Charging Defined by Standards
To start, EV charging infrastructure is largely defined by two main standards. The J1772 SAE standard covers the general physical, electrical, functional and performance requirements to facilitate conductive charging of EVs in North America while IEC 62196 governs similar standards in Europe.
Fast DC charging solution. Image used courtesy of Wallbox
EV Charging Levels
EV charging can be categorized into three different Levels with different power outputs and charge rates:
Level 1 Charging – In North America and Japan Level 1 uses single phase 120 V AC, accessible from a standard residential 3 prong wall socket, to charge the EV through an EVSE (Electric Vehicle Service Equipment) cable and Type 1 J1722 plug that connects to the EV charge port. Level 1 chargers can deliver up to 20 A (2-3 kW @ 120 V) of charge power. This translates to about 5 miles of vehicle range per hour of charge time for a typical EV with 2.5 miles of range per kWh of battery capacity. At these slower rates, Level 1 systems are best used for overnight home charging or shorter-range driving. Note, there is no Level 1 charging in Europe since the standard residential voltage level is 240 V.
Level 2 Charging – These chargers use 240 V AC and are commonly used in public space applications like parking lots, although they can be used in home applications with the proper electrical infrastructure. The Wallbox Pulsar Plus is an example of a Level 2 charging solution. These chargers can be hardwired or connected through a properly rated NEMA plug to a 240 V wall socket. In North America, charge rates with Level 2 systems generally get to about 9.6 kW (40 A @ 240 V single phase) which translates to about 20-25 miles per hour of charge or 4-5 times the rate of Level 1 systems. In Europe, the Middle East and Africa Level 2 chargers use 3 phase AC that can deliver even more power, up to 22 kW (32 A, 3 phase) for residential applications.
Level 3 Charging – Also known as Fast DC charging, this is the fastest way to charge an EV with charge rates well above 100kW. Supernova from Wallbox is a fast-charging solution rated to 130kW that can add up to 120 miles of range to a typical EV in 15 minutes. The Hypernova model (planned for release in 2023) will be a fast charger capable of delivering 350 kW. At 350 kW the GMC Hummer EV pick up with 213 kWh battery capacity can be fully charged in just over 30 minutes. Level 3 achieves these high-power levels by charging at over 480 V DC.
EV Charging Levels. Image used courtesy of Central Hudson
Connecting to the EV Charge Port, Variations by Region
The plug, or connector, is what connects the charge station to the EV, allowing it to deliver power to the high voltage (400 V or more) lithium-ion battery powertrain. The Type 1 J1772 is the standard plug used in single-phase AC Level 1 and Level 2 charging applications in North America and Japan, and supports charge rates up to 10 kW. In Europe, IEC 62196 Type 2 plugs are used for 3 phase AC Level 2 charging applications up to 22 kW.
For DC fast charging the CHAdeMO plug configuration accommodates up to 100 kW and is most common in Japanese models. The CSS (Combined Charging System), or Combo plug, is a clever modification to the J1772 Type 1 plug in North America, or the IEC Type 2 plug in Europe, that adds two extra power contacts to the standard AC connector to support the higher DC charge rates. Due to its versatility, the CSS plug is quickly emerging as the standard for vehicles in North America and Europe. Telsa uses a proprietary plug for its network of fast charging stations but offers adaptors for use with public stations that use either CHAdeMO or CSS.
EV Charging Plug Type by region. Image used courtesy of Blink Charging
The EV charging port will often be configured to accept both AC and DC charging connectors and may have multiple ports. CSS sockets can support both Level 1/Level 2 AC and CSS “Combo” fast DC plugs.
EV charge socket configurations. Image used courtesy of the Driven
EV Onboard Charging Module and DC Fast Charging
Most EVs have an AC/DC converter on board that converts external AC power (Level 1 and 2 charging) to DC for charging the battery powertrain. However, in the case of fast DC charging, utility power is converted to DC externally, so the EVs internal AC/DC converter is bypassed allowing the batteries to be charged directly. In this manner, much higher rates can be achieved since the onboard AC/DC conversion typically limits rates in Level 1 and Level 2 applications.
DC chargers require a lot of power from the grid which can make the costs of operation and installation a lot higher compared with Level 1 or 2 systems. But the benefit is significantly faster charging times and a solution better suited to long range use cases like the US Interstate Highway System. $5 billion in funding was recently allocated through the federal Bipartisan Infrastructure Law to help expand the network of fast charging stations across the Interstate Highway System.
EV onboard charging module for AC and Fast DC stations. Image used courtesy of Springer
Architecture of a DC Fast Charging Station
At its heart, a DC fast charger is a power inverter that converts three phase utility power to the DC current needed to replenish the EV battery powertrain. Typically, line AC power is converted to DC through a controlled rectification stage using an IGBT bridge or similar circuitry. This can be followed by a suitable transformer isolated DC-DC conversion stage that conditions DC power specific to the needs of EV fast charging. Finally, the fast charger communicates with the onboard Battery Management System to properly monitor and regulate the flow of DC power to the EV battery pack.
Fast DC charger architecture. Image used courtesy of Infineon