[Tech Review] Chroma Explains Next Generation EV Charging Technology: ChaoJi Handshakes

Charging protocols are key to the development process of electric vehicles (EVs). In 2010, CHAdeMO was established in Japan as the first charging standard on the market, after which GB/T in China and CCS in Europe and America also joined the game. Together, these three now form the current mainstream charging interfaces that are internationally available. In response to the popularization of EVs and changes in charging needs, in 2019, China Electricity Council (CEC) and the CHAdeMO Association collaborated on the next-generation ultra-high-power charging interface, named ChaoJi. Harmonizing the current major charging systems, the optimized charging safety and power support globalization of the EV charging standard.

Following these reforms in charging standards, Chroma has taken the lead in the research and development of CHAdeMO charger simulators as part of our EV charging test solutions. The simulator is integrated into Chroma 8000 EV Charging Compatibility ATS to meet the test items and communication protocol verification of future EV regulations.

Read more about Chroma 8000 EV Charging Compatibility ATS.

Based on the recent technical developments, the CEC has released a new draft version of the GB/T 27930 regulation part 2 with modifications for ChaoJi and opened it for comments. The specifications show that the ChaoJi charging handshake still adopts the same CAN2.0B protocol as in the GB/T 27930-2015 version and that the protocol data unit (PDU) also follows the frame format defined by J1939-21. However, there are major differences in the charging process, message types, and data types.

ChaoJi offers the following CAN message types and main functions:

• LM (Long Message)
• Used for sub-packaging & regrouping and connection management when multiple information frames are transmitted (data length >8byte)
• SM (Short Message)
• Used for version negotiation
• SM_RM (Reliable Short Message)
• Used to require the receiver to acknowledge with SM_ACK
• SM_URM (Unreliable Short Message)
• Used to indicate that the receiver does not need to acknowledge
• SM_ACK (Short Frame Acknowledge)
• Used when receiver acknowledges an SM_RM
• LM_ACK (Long Frame Acknowledge)
• Used when multiple information frames are transmitted
• LM_NACK (Long Frame Negative Acknowledge)
• Used when multiple information frames are transmitted
• LM_EndACK (Long Frame End Of Acknowledge)
• Used when multiple information frames are transmitted

For the communication process, ChaoJi defines four types of function modules – required, optional, non-overridable, and overridable– as well as the CAN message types used within each module. For example, during the function negotiation phase, the EVCC sends a message type that requires a SM_RM acknowledgement, while the SECC needs to use an LM for handshake.

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