Cell to Pack design for the Mercedes Vision EQXX battery is just one of the aspects that make this an interesting vehicle. OK, this is a research vehicle designed to push the envelope.
With expert engineering and Formula 1 thinking, our battery chemists squeezed the energy of the EQS into the dimensions of a compact car. The battery pack in the VISION EQXX holds almost 100 kWh of energy, yet has 50% less volume and is 30% lighter than the already benchmark pack in EQS.
VISION EQXX – taking electric range and efficiency to an entirely new level, Mercedes-Benz Media
The claims for this battery pack are very significant:
- cell to pack
- lightweight battery case
- air cooled
- ground breaking battery management system
- max system voltage >900V
- Total energy = 107.8kWh
- Usable energy < 100kWh
- SoC Window < 92.8%
- Configuration = 216s 1p
- Nominal Voltage ~788V
- Nominal Capacity ~ 137Ah
Assuming the maximum system voltage equates to the maximum cell voltage of 4.2V, thus suggesting this pack configuration is 216 cells in series. This would then give a nominal pack voltage ~788V and hence a cell capacity of ~137Ah.
- Peak Power = 158kW10s
Taking the peak motor power of 150kW and assuming 95% efficiency gives a peak battery power capability
- Charging
- Fast charge power = 150 kW
- 300km of range added in 15 minutes
- Pack Mass = 495 kg
“The lid is made from a unique, sustainable composite material derived from sugar-cane waste, reinforced with carbon
fibre, as used in Formula 1.”
- Pack Dimensions = 1985 x 1270 x 100mm
- Pack Volume = 272litres (assuming 20 litre for the OneBox)
- Cooling
- Passive air cooling
This post has been built based on the support and sponsorship from: About:Energy, AVANT Future Mobility, Quarto Technical Services, TAE Power Solutions and The Limiting Factor.
A combination of airflow around the battery in the car and a heat sink panel on the base of the battery that wicks away temperature plus little vents on the battery itself, which open to draw in more air as it gets hotter. [4]
- BMS
- Active Cell Balancing “battery management system and power electronics have been designed with an absolute focus on reducing losses.” [3]
- HV Distribution
- OneBox – “The separate compartment for the electrical and electronic (EE) components, called the OneBox, likewise made more room for cells, with added benefits for installation and removal. The OneBox also incorporates novel safety devices with energy efficient operations that consume significantly less energy than the equivalent component in a production EV.”
Metrics
- Gravimetric Energy Density = 218 Wh/kg
- Volumetric Energy Density = 396 Wh/litre
“energy density of close to 400 Wh/l” [3]
The gravimetric energy density of this pack is a testament to having a vision.
- Gravimetric Power Density = 319 W10s/kg
- Volumetric Power Density = 580 W10s/litre
This is a pack optimised around energy and to make this work it sits in a car that is very efficient and hence minimised power demands. Thus giving the opportunity to use passive cooling that reduces the mass of the pack and hence further improves the vehicle efficiency. Engineering and driving this virtuous circle into a vehicle design is inspiring.
References
- Mercedes-Benz’s Vision EQXX EV Does Over 600(!) Miles On a Charge, MotorTrend
- Mercedes Vision EQXX: 621-mile EV concept charts the brand’s future, Green Car Reports
- VISION EQXX – taking electric range and efficiency to an entirely new level, Mercedes-Benz Media
- How Mercedes Built an Air-Cooled Battery for the Vision EQXX Concept, TheDrive
Great innovation indeed. The innovative material, cell-to-pack design, elimination of liquid cooling system and I read they used silicon-based or silicon-graphite anodes which provide higher energy density, leading to unparalleled efficiency. I wonder how they will manage fast charging without active cooling or maybe that Is why it is just a research vehicle that might have to make major changes to be a production EV.