On April 24, the CHAdeMO Association released the 3.0 version of its electric-vehicle (EV) charging protocol. The technology was co-developed by the China Electricity Council as a 600-amp, 900-kW, bi-directional DC quick-charging standard that is harmonized and backward-compatible with all existing standards for the world’s EVs. CHAdeMO was formed in 2010 by five major Japanese automakers and the Tokyo Electric Power Co. It has grown into a global association with more than 400 members.

The project to create an updated quick-charger standard was dubbed ChaoJi – the moniker that would also be used for a new harmonized global DC standard. The project commenced in early 2018 when representatives from China, home to the world’s largest EV market, proposed that CHAdeMO make improvements to China’s GB/T standard. The Chinese National Committee of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) are designated as Guobiao or “GB/T standards.”

An early goal was to increase the mechanical strength of the coupler but reduce its size. In monthly meetings held throughout late 2018 and 2019, CHAdeMO and CEC expanded the goals for the new standard. Those discussions culminated in a gathering of international EV charging experts in Tokyo for the 1st International ChaoJi Technical Workshop in July 2019.

900 kW for heavy-duty vehicles
CHAdeMO had long planned to upgrade its existing 400-kW protocol to the 3.0 version, which would enable a whopping 900 kW of power – with a peak of 600 amps and 1,500 volts – for heavy-duty vehicles, such as trucks and buses. But the association expanded protocols for various levels of power to a wide range of vehicles, as well as charging at homes and workplaces in addition to highway locations.

Tomoko Blech, the European secretary-general of the CHAdeMO Association, in an email to SAE’s Automotive Engineering, explained, “The first vehicle using ChaoJi is expected as early as the end of 2021.” She wrote that the increased capacity of the CHAdeMO 3.0 could be achieved at a reduced cost due to the larger scale of the Chinese EV market.

Blech wrote, “Harmonizing with China’s GB/T is one way to achieve these cost reductions by the economy of scale. China accounts for almost 80 percent of all fast chargers in the world.” CEC members performed the early-stage design work and prototyping. The Chinese and Japanese teams then mutually ensured that the new joint ChaoJi standard would be backward compatible with existing CHAdeMO and GB/T versions.

Test criteria due in 2021
In her email, Blech claimed that “Huge efforts were made to harmonize the hardware, software, and safety requirements of CHAdeMO 3.0 as much as possible with the latest versions of the relevant IEC, ISO, and SAE standards.” Based on successful trials of 500-amp, 475-kW charging in China, a 250-mile EV battery could be almost completely replenished in about 10 minutes.

Project leaders claim that if automakers utilize an 800-volt battery system, twice as much range could be added in the same time. The first demo events and trails – using liquid-cooled connectors and a max current of 600 amps – were conducted at UL Japan Kashima EMC testing laboratory in Chiba prefecture, Japan, on February 6, 2020. The testing criteria for CHAdeMO 3.0 certification, currently being written, will be released in 2021. In the U.S., CHAdeMO has accreditation as a standard managed by IEEE.

Adaptors will likely be produced and sold for Tesla and CCS-compatible vehicles to use CHAdeMO 3.0 chargers. But those would emerge from third-party providers, not as products produced by CHAdeMO or CEC. Tesla has been a member of CHAdeMO since 2012 (Tesla-CHAdeMO adaptors are produced and sold by Tesla). CharIn E.V., the industry group established to develop the Combined Charging System (CCS) as the global standard for charging battery EVs, published a position paper in 2019 opposing any use of adaptors.

Paving the way for vehicle-to-grid
Bi-directional charging, in which power can also be pulled from the vehicle to the grid, has been a fundamental attribute of the CHAdeMO standard since its inception. But it proved to be a challenge for the ChaoJi project. The proposed new coupler reduced the number of pins from seven to four, removing the optional pin that existed in the original CHAdeMO coupler. It had provided 12-volt auxiliary power to bi-directional chargers.

SAE International’s J3072 standards committee is finalizing updates to meet bi-directional charging requirements to the latest IEEE 1547-2018 standard, according to Rich Scholer, SAE Hybrid PEV Communication and Interoperability Task Force chair. The J3072 standard is focused on AC capabilities rather than DC. IEEE 1547-2018 is also used for SAE DC Chargers capable of bi-directional use, Scholer noted.

Under the ChaoJi design, CHAdeMO and China’s GB/T chargers use the same hardware. However, a special inlet adapter and a dedicated bi-directional charging sequence had to be devised to ensure full-backward compatibility of ChaoJi vehicles with the existing bi-directional CHAdeMO chargers that have this optional feature. Blech wrote, “It was quite a challenge to add a new function with the reduced number of signals, while also ensuring robustness, electromagnetic immunity, and full backward compatibility with the existing CHAdeMO, GB/T, and CCS [Combined Charging System] systems.”

Moreover, a control-pilot circuit detects which of the two communications protocols to use, thereby making the two systems compatible. The next step for the ChaoJi project, according to Blech, is to implement full-backward compatibility with the protocol used by CCS for ISO 15118. While the CHAdeMO Association made global harmonization one of the long-term goals, the group understands that it will take automakers, charger manufacturers and charging station operators 10 years or longer to transition to new standards. That’s why backward compatibility was also critical. But ChaoJi is also forward-looking, especially as it relates to next-generation battery technology.

“How the battery systems are designed in addition to compliance with the specification and standards will depend on the strategy of each vehicle OEM,” wrote Blech. “But one thing is for sure. The introduction to the EV market, possibly in the mid-2020s, of solid-state batteries capable of accepting ultra-high charging rate without the expensive thermal management system, will be a significant breakthrough.”