What do we know about the Ehang EH216-S eVTOL battery pack(s)?
At the moment the data is sparse and we appear to have a mix of what battery packs are being used for what tests.
In this post we are primarily looking the Ehang EH216-S battery for which the airworthiness certificate from the Civil Aviation Administration of China (CAAC) was received on 13 October 2023 . INX solid state cells with a claimed 480Wh/kg is briefly discussed at the end of the article.
Aircraft
- cruise speed = 100 km/h (62 mph)
- maximum speed = 130 km/h (81 mph)
- maximum altitude = 3,000 m (9,843 ft)
- range = 35 km (22 miles) based on a flight time of 21 minutes
- aircraft has 16 propellers, 16 electric motors and is powered by batteries
- Power
- VTOL power = 155.7 kW
- +16% increase in installed power to tolerate an engine failure for a total of 180.6 kW [4]
- Cruising power = 93.4 kW
- VTOL power = 155.7 kW
- maximum takeoff weight = 620kg
- maximum payload of the aircraft = 220 kg (485 lb)
- fuselage made of carbon fiber composite
- fixed skid landing gear
- 2024 official guide price of the EH216-S in China is RMB 2.39 million ($330,000)
Battery Packs
The fact that the Ehang 216-S has 16 motors and 12 batteries suggests that this is not a completely independent system design. We need to understand the details of the Redundant Smart Battery Management System that is described by Ehang:
The Battery Management System (BMS) can monitor the status information including battery voltage, current and temperature in real time and control them within a safe range, thus effectively extending the service life of the battery. Meanwhile, the 12 batteries are combined as a system to provide safe and reliable power. Even in the event of failure or malfunction in 1 or several of the batteries, the battery system can still operate stably and
reliably and provide sufficient power for the aircraft.
- 12 batteries
- Energy = 17kWh
- recharging time = 120 minutes
This post has been built based on the support and sponsorship from: Thermo Fisher Scientific, Eatron Technologies, About:Energy, Quarto Technical Services and Alvatek.
Analysis by Paul Moller [4]: The energy required to cruise at 81 mph. for 9.9 miles is 11.4 kWh, providing a 20% reserve to protect the payload and batteries and 2.7 kWh to operate for one minute (2 x 30 seconds) at VTOL power requires a battery energy of 16.9 kWh. This agrees with the Ehang installed battery energy. The Ehang’s very short range is a consequence of its limited battery capacity and the low lift/drag ratio of rotary wing aircraft.
Solid State
Ehang are targeting certification and mass production use of IHX solid-state batteries in the EH216-S by the end of 2025. The increase in energy density increases the flight time from 21 minutes to 48 minutes as demonstrated in Ehang’s latest flight tests. Maybe the claimed 480Wh/kg at cell level is approaching the future targets.
Electrified Aircraft Propulsion Targets
- 400 Wh/kg required at the system level
- 1000’s of cycles
- Extremely high power requirements (C-rates) during takeoff and landing
- Cruise power for long range flights
- High reliability, limited maintenance
- Improved safety for thermal runaway events
References
- Ehang 216-S passenger eVTOL, Ehang
- Ehang completes 1st ever flight test of eVTOL powered by solid-state batteries, CNEVPost
- 1st Autonomous, Electric Aircraft In World To Get Approval For Commercial Flights, Cleantechnica
- Paul S. Moller, REVIEW OF SELECTED PERSONAL AIR VEHICLES,
Just 17 kWh on an aircraft with a 620kg max takeoff weight seems small. That is less than 100kg of battery on a 200 Wh/kg battery pack, and I would expect more if it’s using solid-state batteries.
100kg of battery for a 400kg base weight feels reasonable, the flight time / range is low. The solid state version they have tested has a flight time of more than twice this version. Doesn’t mean double the energy as the cruise power is lower than takeoff and hover power. I will update once we know more.