Better Together: Electric Aircraft Charge Connector Standardization

We are currently witnessing the transition to electric and autonomous technologies, revolutionizing all forms of mobility. The impact of electrification within the automotive industry has been profound, and it’s just a matter of time before the wave of new technology completely disrupts the aviation industry. Drawing a parallel between the two, the purpose of this article is to make the case for charge connector standardization, with the aim of avoiding the messy early years of electric automobiles. An examination of early electric aircraft design suggests that without industry-wide cooperation, we may be in danger of repeating the same ugly history in aviation.

While not an exhaustive list, the vast majority of electric vehicles on the road today use one of these seven charge connector types:

  • Tesla Specific
  • Type 1 (J1772)
  • CCS 1
  • Type 2 (Mennekes)
  • CCS 2
  • CHAdeMo
  • GB/T

There are many reasons why the world has been slow to standardize on electric automobile charge connectors, including the distinction between AC and DC charging, variations in power capability, and regional standards bodies believing they each have a better solution. For consumers, the lack of a single standard compels motorists to carry a variety of frustrating adaptor cables, anticipating the possibility of charging at stations with mechanically incompatible connectors.

The automotive industry is finally beginning to clean up the mess of charge connectors, with the consensus moving toward a “Combined Charging System,” specifically “CCS2,” in both Europe and the Americas. Even Tesla, which has been slow to conform its designs to an outside standard, has demonstrated support for the new CCS2 standard by including the connector with Model 3s sold in Europe and Singapore. Capable of charging rates of up to 350kW, the CCS2 and DC supercharger allow a Model 3 to add 200 miles of range in only 25 minutes: not quite as fast as filling a car with gasoline, but getting much closer.

Image: Tesla Model 3 with CCS Combo 2 Charge Connector

In Asia, the Japanese, who drove the CHAdeMO standard, and the Chinese, who drove the GB/T standard, have joined forces to create yet another connector standard, currently known as “ChaoJi.” The ChaoJi connector is said to offer a 900kW power rating (2.6x higher than CCS2), and up to 1,500V charging (compared to 1,000V for CCS2), which reduces wire gauge and cooling requirements. Final specifications will be released in 2020, and electric vehicles with ChaoJi connectors are scheduled to appear in China and Japan in 2021. Given the current geopolitical situation, it seems unlikely that this connector will find mass adoption by Western countries, and we will be left with at least two standards to address the needs of most electric vehicles.

Image: Prototype of the future “ChaoJi” charge connector (courtesy of Car Watch, Japan)

As the industry matures, however, both ground and air vehicles will soon scale to sizes that require more than the 350kW charge capability of CCS2. Several companies have announced intentions to develop large-scale electric trucks, including Daimler, Renault, Volvo and Tesla. Based upon Tesla’s stated range of 500 miles for its new semi-trailer truck, industry experts estimate the platform to have a 1,000kWhr battery. “Megacharging” such a beast in 30 minutes will require at least 2MW of power.

In the field of electric aircraft, Eviation recently unveiled its 9-passenger Alice airplane at the Paris Airshow. With a similar sized battery of 900kWhr, the Alice will also require a 2MW charger to turn the aircraft in under 30 minutes. As these examples illustrate, there will soon be a demand for very high-powered DC charging, one which clearly exceeds the capabilities of both CCS2 and ChaoJi.

ChargePoint, recognizing the emerging market opportunities for both electric trucks and aircraft, introduced a 2MW charge connector concept at the 2018 Uber Elevate conference. According to Pasquale Romano, ChargePoint’s CEO:

“The ChargePoint engineering team focused on several key elements in developing the new design. To meet performance requirements, up to four BMS interfaces and four 500-amp delivery circuits are needed. Each delivery circuit will have a voltage range from 200 to 1,000 volts. To facilitate autonomous data and vehicle performance payload offload, a provision for high speed data transfer was also included. Designed to be used in heavy vehicle applications, the connector must be rugged and able to withstand the rigors of frequent use, while also being easy to insert and remove.”

As the operator of the world’s largest electric vehicle charging network, ChargePoint has clearly taken its many years of real-world experience and applied it to the requirements for next-generation “megacharging.”

Image: Chargepoint 2MW charge connector (courtesy of Chargepoint)

ChargePoint is committed to supplying charging solutions for the future Uber Air eVTOL taxi service, targeted to launch in 2023. Demonstrating growing commitment toward the ChargePoint 2MW charge interface, Safran showed a prototype of the ChargePoint connector as part of its eVTOL cabin display at the 2019 Uber Elevate conference in Washington, D.C.

But ChargePoint is just one player in the ecosystem, and in order to spur mass adoption, a worldwide committee-driven standard for megacharging is required. The standards body behind CCS2 is CharIN, an association with over 150 members from the entire electric vehicle value chain. CharIN formally established a requirement specification for High-Powered Charging of Commercial Vehicles (HPCCV) in February 2019. Unfortunately, the power specification reflects a stated need of 1MW or greater, rather than 2MW or greater, a disappointing development given the immediate needs of emerging trucks and aircraft with 1,000kWhr batteries. CharIN has not yet publicly disclosed a design choice, though the period to accept HPCCV proposals closed in May 2019. In my view, any design announcement less than 2MW is likely to send the CharIN working group back to the drawing board, as customers like Uber Air will prefer the heftier ChargePoint solution, even if it remains proprietary.

It’s difficult to overstate the importance of fast charging aircraft. In the world of electric passenger automobiles, at-home “trickle charging” is common, since electric automobiles typically have enough range for drivers to complete their daily routine and return home with reserve. The same, however, cannot be said for electric aircraft. Even an amateur pilot enjoying a weekend hobby will be limited to flight times of one hour or less in the first-generation aircraft. Pilots wanting to fly longer (or make round trips to nearby destinations) will want to supercharge to get back in the air as quickly as possible. And for air taxi operators and flight training schools, supercharging is a must. Otherwise, the downtime for charging could equal or exceed the flying time. This means an immediate demand for chargers capable of at least 2C rate power transfer.

So far, each airframe company appears to be developing their own proprietary charging solutions by necessity, and most of these solutions do not currently offer 30-minute recharge times. But in order to effectively grow the market for electric aircraft, leveraging the DC supercharging efforts of the automotive industry is the logical strategy. Given the broad acceptance of CCS2 for electric automobile charging, it only makes sense that all aircraft with batteries of 175kWhr or less should also use the CCS2 connector, and be capable of communicating and charging from automotive CCS2 DC superchargers. The 175kWhr capacity ensures the desired 2C rate when charging at the maximum CCS2 power.

For vehicles with a battery capacity greater than 175kWhr, up to the 1,000kWhr capacity expected for 9-passenger aircraft, the proprietary ChargePoint 2MW connector and their future “megacharger” appears to be an ideal solution, both for aviation as well as trucking. Early support from the Uber Elevate partners demonstrates a trend in the eVTOL market. That said, if CharIN HPCCV emerges with an equal or better connector design, including 2MW+ power capability, then the industry may yet shift in this direction.

One additional hurdle worth mentioning is regulatory approval. The FAA and EASA each have yet to weigh-in on certification requirements for third-party DC superchargers, though certification remains a logical requirement to ensure aircraft safety. Unlike the case of AC charging, where the vehicle’s onboard charger manages the proper charge profile, DC supercharging puts the battery under the management of the external charger. Exceeding the maximum charge voltage or current, for example, could damage the aircraft battery and create a safety risk. Hence, some amount of FAA and EASA oversight is likely warranted.

As with most things in electric aviation, the details are continuously evolving. If we in the industry want to encourage rapid adoption among all of the users of electric aircraft — general aviation pilots, flight schools, and air taxi operators — consensus-driven standards will be required. Perhaps the General Aviation Manufacturers Association (GAMA) is the best group to form a working group to address this standardization issue for the aviation industry? If anyone from GAMA EPIC is reading this and wants my help, please give me a shout!