How to boost Level-3 EV charging with the right connectivity

Fast charging entails the transferring a large amount of energy into the battery at a high rate. The method used to charge the battery, as well as the battery chemistry, determines the power level at which a cell can accept a charge. Several approaches have been developed to prevent or decrease harm caused by significant energy flow at high power. Constant-current/constant-voltage (CC/CV) and pulse current charging are the most common charging methodologies.

Vehicle Electrification

he charging speed depends upon three components - the charging station, the charging cable and the on-board charger. Connectors and power ratings are the two things which need to be considered for EV charging. Level 3 charging is the fastest type of charging available which can recharge an EV at a rate of 3 to 20 miles of range per minute. Most Level 3 chargers provide an 80% charge in 30 minutes. This type of equipment is not compatible with all vehicles, and the charge itself is not accepted by all vehicles. The EV charging connector should have low contact resistance, high thermal support and component modularity in order to prevent the losses, it has to meet the required current and voltage ratings. Cable solutions are ultrasonically welded and provide current carrying capacity up to 200A/contact to the heavy-duty AC/DC power inverters.

Figure 1: Charging system configuration for electric vehicle

Level 3 Charging, most commonly known as “DC Fast Charging” as shown in above figure, DC Fast Charging bypasses all of the limitations of the on-board charger and required conversion, instead it provides DC power directly to the battery. Charging times are dependent upon the battery size and the output of the dispenser, plus other factors. The higher the level of charging, the faster the charging process, as more power is delivered to the vehicle. One of the main barriers to EV acceptance is range anxiety, which can be alleviated by fast charging (FC). The main technology constraints for enabling FC consist of high-charging-rate batteries, high-power-charging infrastructure, and grid impacts. The table below depicts different EV Charging Speeds for different Level 1, 2, 3 Chargers along with other comparison facts.

Table 1: comparison of different EV charger levels

The level 3 off-board charging infrastructure will alleviate the down-time required for vehicle charging, it is necessary to choose suitable power electronic interfaces for these chargers to prevent any potential damage to the grid, and optimize system efficiency.

Level 3 EV charging connectors

Standards for EV charging connectors have been developed to standardise the format for maximum interoperability. DC fast chargers have multiple standards for connectors, the leading standard is the charging Interface Initiative (CharIN)’s standard, called the Combined Charging System or CCS. It also specifies a powerline communication (PLC) implementation for charging control and safety measures which use pulse-width modulation (PWM). For fast charging as depicted in below figure, the CHAdeMO and SAE Combo - CCS for “Combo Charging System” are the most used connectors by electric car manufacturers.

Figure 2: a) Level 3 CHAdeMO connector, b) Level 3 SAE Combo CCS Connector

• CHAdeMO

CHAdeMO is a DC charging standard protocol enabling EV charging. It enables seamless communication between the car and the charger. CHAdeMO is Smart ‘Grid-ready’ through its bi-directional charging capability. It is also compatible with any local or optional functions beyond charging. The protocol works with CAN communication, onboard communication network for all EVs, making its integration with the rest of the car easy and reliable.

It is tasked with safety certification, ensuring compatibility between the car and the charger. Level 3 equipment with CHAdeMO technology, charges through a 480V, direct-current (DC) plug. CHAdeMO-equipped EVs require an additional J1772 connector cord to achieve Level 1 or 2 charging.

CHAdeMO 1.2 supports High power charging (200kW), including protection against over-temperature, overload/short-circuit current protection, coordination and ground fault detection, as well as vehicle-side impedance requirements. CHAdeMO 2.0 (current version) supports High power charging (up to 400kW), enabling large commercial vehicles including trucks and buses, compatible with plug-and-charge functionality.

• Combined Charging System (CCS)

Shortly after the CHAdeMO was introduced, a second connector called the CCS was implemented as an additional charging standard. The CCS is based upon open and universal standards for electric vehicles. The CCS combines single-phase AC, three-phase AC and DC high-speed charging in both Europe and the US – all in a single, easy to use system. CCS connectors allow for AC/DC charging on the same port. The CCS includes the connector and inlet combination as well as all the control functions. It also manages communications between the electric vehicle and the infrastructure. As a result, it provides a solution to all charging requirements.

New generations of DC fast chargers (DCFCs) can produce 150-350 kW of power by using the Combo 1 and Combo 2 connectors. Some in Europe are even reaching 400 kW. It’s important to note that not all EVs are currently equipped for DC fast charging, although most all new EVs hitting roads do support it.