As AAM aircraft move closer to production, competing charging standards come to the fore.
In the fall of 2023, the industry offered three different charging standards to the Advanced Air Mobility (AAM) community. Each system has been in development for a long time, at the end of October 2023 in Augsburg, Germany. electro.Aero provided an update on the progress of the SAE International Working Group's multi-year meeting to develop standards for charging electric aircraft. Two weeks later, Joby and Beta unveiled the details of the different charging systems they were pursuing.
This article outlines the three main methods. But first, a quick recap of the empty ** car rental ecosystem for Uber Elevate's first comprehensive framework and proposed charging system. It is worth noting that after Jopy inherited the work of Uber Elevate, the GEACS charging standard developed by it is a supplement to the current competition of aviation charging standards, rather than a homogeneous ineffective work.
chargepoint（uber elevate）
In January 2018, at VFS's 5th Annual EvTOL Symposium, Chargepoint's Alan Dowdell mentioned the differences between AC and DC charging standards for cars and other charging systems, and hoped that the EVTOL industry would not repeat the mistakes of the past.
ChargePoint has developed a 2-megawatt charger concept for Uber Elevate.
At its first Elevate Summit in April 2017, Uber announced a partnership with ChargePoint, which bills itself as "the world's leading and most open EV charging network," as well as an increase in battery reserves in seven minutes.
These high-powered fast charges will supplement the energy used in each flight, and the empty ** car rental supports hours of operation by continuously "topping up" the battery to a state of charge of approximately 80% between each pick-up and drop-off;Then, it can be fully charged before each "rush hour" travel demand surges.
ChargePoint unveiled its 2MW high-power charging concept design for electric semi-trucks and eVTOL aircraft at the second annual Elevate Summit in May 2018. To meet the performance requirements, up to four BMS (battery management system) interfaces and four 500A transmission circuits are required. Each transmission circuit has a voltage range from 200 volts to 1000 volts. In order to facilitate the offloading of autonomous data and complete machine performance payloads, high-speed data transmission is also included. Connectors must be robust and easy to insert and remove. In addition, the connector supports optional auxiliary liquid cooling for aircraft or semi-trucks while they are charging.
ChargePoint's approach may not be adopted after Uber terminates its Elevate program.
SAE international standards (ARP6968 and AIR7357).
SAE International (originally founded in 1905 as the Society of Automotive Engineers) is an internationally recognized standards development organization (SDO) with more than 240 technical committees and draws on the expertise of nearly 9,000 volunteers. SAE and other SDOs are already setting charging standards for electric vehicles around the world.
Tesla, the best-selling electric car manufacturer, has developed a proprietary system, so most other cars in North America use the Combo 1 (CCS1) combo charging system, which combines a previous-generation round AC plug with a DC fast charging port. In the European Union (EU), it is mandatory to use an incompatible version of Combo 2 (CCS2) (even for Tesla), and the GB T 20234 AC/DC charger is the only system allowed in China, which produces the most electric vehicles in the world. Japan also has a chademo DC charging standard.
However, in November 2022, Telsa opened up its proprietary connector design to the public, calling it the North American Charging Standard (NACS) connector;This is the (draft) SAE J3400 connector that is now publicly available. Since then, most major car companies have announced that they will equip cars sold in North America with NACS chargers, with the exception of Mazda, Mitsubishi, Stellantis (Chrysler, Fiat, etc.) and Volkswagen Group. Tesla cars in Europe use the CCS2 standard, while Tesla cars in China use the GB T standard. As a result, NACS will not only become the SAE standard, but will become the de facto standard that will be used in almost all new cars in North America.
Several standards for EV charging connectors.
Australian developer of electric aircraft charging systemsAero began working with SAE International in February 2019 to develop an industry standard for aircraft charging. Joshua Portlock, co-founder of Electro Aero, led the SAE AE-7D Aircraft Energy Storage and Charging Committee on the development of the aerospace recommendation ARP6968 "Light Electric Aircraft Conductive Charging Connection Kit" for aircraft charging requirements up to 500 kW;It is expected to be finalized in 2024.
Mobile charging units sold by Electro Aero provide continuous charging power from 7 to 240 kW. The units can be interconnected with SAE ARP6968 as well as automotive CCS1, CCS2, and GBT charging standards, and the units can be reconfigured between standards. Electro points out that the car CCS charger doesn't work unless plugged horizontally, has a large, heavy outlet with unused AC pins, and doesn't have a 28V auxiliary power supply;In addition, there are two separate standards, CCS1 and CCS2.
A megawatt-class charging system (MCS) for heavy-duty electric buses and trucks could be the basis for the planned Air7357 standard.
Although SAE's ARP6968 connector is based on the Chinese GB T DC plug, Electro.Aero highlighted the benefits of the new standard for aircraft. Benefits include higher voltages (up to 1000 volts), aviation-standard 28 volt auxiliary power that stays on after charging is complete for better battery health and automation, the lock activates as soon as it is plugged in and automatically starts charging, and it can charge up to 1785 batteries (7 times higher than the GB T limit).
The SAE Commission is currently preparing an Aerospace Information Report (AIR) for aircraft that require more than 500 kilowatts. The air7357 "Megawatt and Extremely Fast Charging for Aircraft" was launched in November 2020. SAE** elaborates on its rationale: "Current standards (AS6968, J1772, etc.) do not include the power levels required for extremely fast charging (XFC) for medium-sized aircraft applications (150 to 200 kWh batteries are charged at 5 degrees Celsius or higher) and evolving commuter and single-channel concepts (500 kWh to > 1 MWh for charging at temperatures of 2 degrees Celsius or more). There is a need to understand the design considerations for this type of charging and establish use cases for this type of charging to help the industry develop appropriate device standards.
Several standards for EV charging connectors.
Similar to how the ARP6968 is physically based on the GB T automotive standard, the Air7357 standard is currently exploring the use of the Charging Interface Initiative (Charin) Ev.Coupler developed for automotive megawatt charging systems (MCS) for heavy-duty electric buses and trucks, although SAE J3271 is still working on it. It is important to note that this discussion relies on a fluid-cooled charging cable to achieve 35-A above, but the fluid does not pass through the triangular charging plug. As the MCS J3271 has not yet been finalized, the aerospace-grade air7357 is still in early development;It is not expected to be finalized within a few years.
Flyone has been operating a fleet of two-seater electric Pipistrel Alpha Electro training aircraft commercially for several years. It uses a portable external air conditioner, which is piped to the battery air intake, to cool the battery in Australia's summer heat – often over 35°C – which avoids the battery from overheating while charging and reduces capacity drops. This solution is simpler, lighter, more reliable, and less expensive to maintain than liquid-cooled systems, so exterior air conditioning for small aircraft should be considered whenever possible.
Joby Aviation (GEACS).
Uber invested in Joby in 2020 and then spun off its Elevate program, transferring personnel and intellectual property to the empty ** car rental company. With lessons learned from Uber's nearly five years of UAM research and development, Joby focuses on fast charging, as well as charging methods that facilitate optimal battery conditioning in multiple sets of redundant battery systems to maximize the productivity of its aircraft, with the aim of keeping it in the air as much as possible to earn revenue.
In addition, for safety and redundancy, Joby distributed four detached, isolated battery packs in the wings and forward power nacelles, repeated their design over the past decade, and developed the originally planned proprietary system. At the end of the summer of 2023, Joby decided to open its Global Aviation Charging System (GEACS) specification to the world;Maybe it's because more and more complete machines are about to be certified, and seeing the example of Tesla, opening up a standard that allows evtol infrastructure to develop, or other business reasons. Joby began reaching out to other Evtol Original Equipment Manufacturers (OEMs), with several other companies expressing interest in Jody's integration approach.
Joby published an overview of the GEACS specification on November 7th. The key to this approach, Joby said, is "the benefits of integrated battery conditioning, security and high-speed data offload, which is expected to meet the safety and cybersecurity requirements set forth by the FAA, as well as the ability to charge multiple independent battery packs simultaneously." Isolating the battery module and these other features will result in a "lower certification burden", although others question the proximity of the coolant and high-voltage charging cables.
Joby GEACS integrated charging connector.
Jopy's GEACS may compete with MCS within the SAE Air7357 standard, as it is still in the early stages of information reporting. To be efficient in terms of weight and charging time, megawatt-class aircraft may require off-board liquid cooling for battery conditioning.
Joby has released a flyer on the technical details of its charging system, highlighting its approach and benefits, saying that the Ethernet connection ensures that the vast amount of data generated by the aircraft can be done quickly and securely**. Fluid couplings and electrical connectors are designed to minimize the complexity and forces involved in connection and disconnection.
In addition, GEACS includes the exchange of coolant with an external temperature control source, thereby maintaining the unit battery pack at the ideal temperature throughout the charge cycle, without the need for a full on-board thermal management system. This is the same as pre-flight pre-conditioning, enabling fast charging with minimal impact on battery life. It is designed to output 150 1000 VDC and up to 300 A through each of its two channelsSince the Joby S4 has four batteries, it needs two connectors at a time, each charging and cooling two separate battery packs at the same time.
And, of course, the weight of the residual liquid ("deionized 40% ethylene glycol with preservatives"), as well as pumps and controllers inside the aircraft. On the other hand, for UAM tasks that require fast charging, if there is no integrated liquid cooling system in the charging connector, a separate system must be connected to circulate the coolant, for example, the liquid may be flushed out of the aircraft battery system with air. In addition, small electric conventional or short take-off and landing (ECTOL or ESTOL) aircraft that do not require a quick turnaround may not require liquid cooling at all. Surprisingly, Lilium claims that its eVTOL aircraft are designed to be designed without the need for external cooling.
Beta Technology (CCS).
Based in Burlington, Vermont, Beta has been outspoken about its charging infrastructure plans and progress over the past few years. In addition to flight test prototypes of the A250 EVTOL and CX300 Alia ECTol aircraft, Beta also unveiled its first elevated landing platform installed with crew rest stops, office space, and energy storage batteries in 2019. Beta has built a network of 15 charging stations from Vermont to Florida or Arkansas, and in October 2023 flew the Alia on a 3,200-kilometer flight to the U.S. Air Force's Duke airfield. Beta will install chargers at 55 additional locations on the East Coast and Gulf Coast and in California next year, with plans to continue expanding the charging network.
Beta has been using the CCS1 standard for its electric aircraft, having been installing multi-mode charging stations that can be used in airplanes or cars. The BETA's charging module is also designed to be up to 1000 VDC, with a continuous power output of 320 kW that will charge the ALIA aircraft in 50 minutes.
Beta now also has a Mini Cube, designed as a stand-alone Level 3 DC fast charger that can be used with all CCS units (including air and ground vehicles), providing 60A, 40kW of continuous output power.
There are significant architectural differences between Beta's ALIA, Archer's Midnight, and many non-VTOL AAM companies. While Joby has four separate battery packs, other companies have opted for a parallel battery architecture for charging. Designs such as the Alia and Ampaire Eel Eest test benches have battery packs underneath the cockpit, reminiscent of Tesla's "skateboard" configuration. This helps to better connect the external cooling system. Beta has a thermal management system that plugs in separately from the charger, which gives OEMs more flexibility when designing their cooling systems.
On November 7, Beta and Archer announced their collaboration to accelerate the adoption of interoperable charging systems across the electric aviation industry and advocated for the CCS-based standard as the single global standard for EVTOL charging.
BETA's CCS1 connector header.
GAMA released a report in August 2023 titled "Interoperability of Charging Infrastructure", which was signed by 13 AAM companies. The signatories noted that while charging needs will change over time, the focus here is on the benefits of shared, compatible, or interoperable infrastructure, and committed to using CCS1 plugs in North America and CCS2 plugs in Europe. Although the two plugs are not compatible with each other without an adapter, the charger will be interoperable with all aircraft using local CCS standards.
The EuroCAE standard ED-308, titled "Guidelines for VTOL Charging Infrastructure", was published in February 2023. The document includes minimum requirements for EVTOL charging infrastructure for verticase take-off and landing. The technical standard confirms that CCS2 (EU Authorized Standard) is suitable for electric aircraft charging and is "an off-the-shelf solution." As a second step, a future publication of the document will extend the scope to the MCS once the standard has been fully described and matured.
Where are you going?There are at least 10 different types of EV plug configurations in active use worldwide. Wisk Aero says that while its original aircraft used the CCS1 standard, Wisk has also designed a system very similar to the one demonstrated by Joby for use in its production EVTOL aircraft.
It is clear that there are different options when it comes to chargers to install in the future AAM infrastructure. If other OEMs think it's better to integrate coolant into the charging connector, then products like GEACS may be more widely used. If not, CCS1 in North America and CCS2 in Europe could become ubiquitous aircraft charging plugs in the short term, until ARP6968 could become an internationally recognized standard. Time will tell if they will coexist peacefully in the short to medium term, whether there will be a unified megawatt-class charge coupler in the future, or whether there will be some kind of ** authorized standard in the countries where the AAM operates, as is the case with electric vehicles in the EU and China.
While initial OEM decisions are always centered around the entire aircraft, SAE standards are developed by charging manufacturers, who have a number of aircraft manufacturers as customers who support them extensively. The ideal solution is that the best overall charging standard will be universally accepted internationally, rather than country-specific or machine-specific.
Article **From: Aviation House