Analysis of the Ferrari Battery Patent
Ferrari Battery Patent US 11,220,169 B2. Images reconstructed by Cecile Pera based on the original patent.
It is not a secret, Ferrari is working on Full Electric Vehicles. Despite the reluctance of the purists, John Elkann, CEO of Ferrari, has announced that Ferrari will launch its first pure-electric sport car in 2025. Obviously, Engineers have to come with new ideas and innovation to bring the Ferrari philosophy towards Electric Motors and Battery development. So far, we have not learnt so much about what Ferrari is doing but a recent patent granted in January 2022 gives us a sneaky peak into Ferrari BEV development program.
This article is based on a Patent (US 11,220,169 B2) published by Ferrari and granted on 11 January 2022. Under the very general title “Electric and Hybrid Sport car” is hidden several developments made by Ferrari. The main innovation of this patent is to relocate a structural element of the vehicle on the Battery pack. For this, the Battery Pack is completely redesigned and consequently presents several interesting features. Besides this primary objective, Ferrari is also addressing in this patent several key elements for their brand: how the Battery Pack can (indirectly) enable a better aerodynamics (!) and how the mass repartition can be optimised to offer the best drivability for their customers…
The Global Ferrari Battery Pack Design
Ferrari Battery Pack - Right: sketch extracted from the Patent US 11,220,169 B2; Left: rendering reconstructed by Dr Cecile Pera. The Battery pack consists of 2 parts: (1) a flat under-floor and a chest installed behind the seats.
The first element of the Ferrari Patent is the global design of the Battery Pack. The patent shows several drawings explaining the global design and also the packaging details. From the patent, we have reconstructed a rendering of what the Ferrari Battery Pack could look like…
The Pack consists in 2 separate parts: (1) a flat-floor on top of which a (2) chest is installed. The flat front part (1) supports on its upper part the passenger seats, while the chest (2) is placed behind the passenger seats as shown in the next image below. Please note that Ferrari adds in the patent that “even though the figures do not show any IC Engine, it can be housed in the front part of the car or behind the rear battery pack”, meaning that this configuration could be applied not only for a full Electric Vehicle but also to a future Hybrid high-performance Supercar.
If the general Battery Pack does not look like anything I have seen so far, we can ask ourselves what is the difference between this pack and an usual Battery Pack? Is that architecture completely new? Battery packs can be organised into 3 configurations which can be mixed and matched:
The under flat-floor: this is the most common Battery Pack in today’s BEV and is commonly labelled as a “skateboard platform” (EV Card EV31);
The tunnel: this is an elongated battery installed in the middle of the vehicle between the left and right passengers within the traditional transmission tunnel. This is, for example, the configuration proposed in Audi A5 e-tron Auattro Plug-in-Hybrid back in 2011;
The chest: this is a chest-shaped (as in treasure chest) battery usually placed behind the seats. This configuration is very common in Hybrid and high performance cars such as the McLaren Speedtail, for example.
Here, Ferrari is combining the configurations 1 and 3. But why doing that?
The underfloor (1) offers a very low centre of gravity but spreads battery mass everywhere in-between the front and rear axles. This is rarely (never?) the configuration chosen by high performance EV. Usually, Supercars prefer to keep the centre of mass in the same location as most ICE HyperCar = behind the driver for better drivability and “feeling”. This is why most of the existing Electric supercars (for example, Lotus Evija) have a Chest-Battery configuration, as well as most Hybrid SuperCars, notably the Ferrari SF90-Stradale.
Yet, Ferrari is not the first manufacturer to propose a High-Performance fully electric vehicle that combines multiple battery configurations: the RIMAC Nevera, for example, combines a large chest (3) with a long tunnel (2) and a very small underfloor flat (1). Even keeping it to the combinaison of a large chest behind the driver and an extended underfloor, Ferrari is not introducing a never-seen approach: the recently presented Leva project by Lotus has the same philosophy. The Aspark Owl is another example of an EV SuperCar with a Battery combining a chest and flat floor. The next ETCR Battery developed by Williams Advanced Engineering is also using the same approach.
In some extent, you also can say this is the architecture developed by AUDI in their Dakar RS Q e-tron except that the chest part was in-between the copilot and the driver (where you would normally find the transmission tunnel of a traditional ICE vehicle).
As you can see, this is not where this patent introduces a unique innovation.
The Breakthrough in the Battery Floor
Ferrari Battery side view extracted from the Patent US 11,220,169 B2. The Battery Pack is a rendering reconstructed by Dr Cecile Pera.
When looking at the Battery Pack from the side, you can see that the Battery underfloor is not horizontal but instead tilted with a slight angle making the chest upwards at the rear of the vehicle. The patent claims an angle from 1 to 5 degrees but mentions that it is ideally 3 degrees. This angle is created at the junction between the front and the rear parts of the Battery Pack thanks to a special design. This allows to move the chest progressively further from the ground when going towards the back of the car (= what is usually called a “diffuser”), allowing the flow of air beneath the car to accelerate, thereby creating a low pressure under the rear of the Supercar and generating some downforce. The patent claims that ‘This fact improves the aerodynamic load of the car”.
It is important to notice that the chest does not follow this inclinaison but on the contrary stays perpendicular to main structure. This is very important to understand from a structural point of view.
ETCR Battery Pack designed by Williams Advanced Engineering
How innovative is this “non-flat” Battery casing bottom by Ferrari? Is that “disruptive”? Unfortunately, not really… Ferrari has not made the first “none-flat” housing even not the first Flat Floor (config 1) with a chest on seating on the top (config 3). For example, this is what is already used in the FIA ETCR ( eTouring Car World Cup is a touring car Series for Electric Cars) launched in 2021. The Battery Pack was designed by Williams Advanced Engineering (WAE) and already features a Chest + Skateboard structure with a rear chest slightly upwards. In some sense, the WAE configuration is much more advanced as it is based on a complete moulded composite, not reduced to feature a unique angle to tilt the rear of the pack but allowing a complete complex design to fine tune the aerodynamic of the cars.
The Structural Elements in the Ferrari Battery
Ferrari Battery Pack sketch extracted from the Patent US 11,220,169 B2. Highlighted are Structural elements in the Battery bottom casing that can be plugged to the main vehicle frame thanks to the clips circled in purple. All the cohesion forces converge towards the centre of the battery bottom plate.
So, what is exactly the Ferrari Patent about? As described in the main claim of the published patent, Ferrari proposes to incorporate some structural elements (called SBR in the Patent) of the vehicle frame inside the Battery Pack and this is where the true innovation sits.
These structural elements (highlighted in pink in the image above) are housed in the rear part of the vehicle. These rear oblique side members, once associated with the rest of the main vehicle frame, participate to the full definition of the chassis structure. On the floor of the vehicle, they define triangular structures (shown in grey on the picture). As triangular structures are extremely rigid and stable, this innovative structure enables a very rigid floor and help the vehicle stability at high speed.
You can notice that all the structures converge toward the same central point referred to by Ferrari as the Central Converging point (called CTRN in the patent). Please note that the SBR are strictly part of the Battery casing (Ferrari says that they are manufactured as “one single piece together with the base”). The SBR are designed in such a way that they can absorb a part of the stress transferred to the frame by the suspension which is brilliant! According to Ferrari, they also contribute to absorb the Battery Pack deformation in case of an impact (even if I imagine the rest of the frame should include other elements for Battery protection and crash-worthiness).
These structural elements can be plugged to the main frame of the vehicle thanks to 2 specific pairs of flanges (circled in purple in the image). The rear flanges are connected to a rigid portion of the chassis commonly known as "rear tower" to which a rear suspension is usually fixed. The front flanges are attached from the vehicle main frame to the central node of the pack. Of course the edge of the Pack is also attached thanks to multiple screws as it is usually the case with all Batteries.
What Cells will Ferrari use?
Ferrari Battery Pack extracted from Patent US 11,220,169 B2. The right view with cylindrical cells was made by Dr. Cecile Pera for illustration but does not correspond to any real configuration.
For the flat bottom part including these side bars, packaging large cells is impossible and we understand that the lower Battery housing has to be filled with cylindrical cells (the patent says “the cylindrical shape of the single cells is particularly advantageous to occupy all the space available”).
Nevertheless, the fact that the Battery floor is filled with cylindrical cells does not necessarily imply that the rest of the Pack also consists of cylindrical cells. The Ferrari patent clearly says that the rest of the Battery Modules can use Cylindrical, Prismatic or Pouch Cells. Ferrari even mentioned that it is particularly advantageous when 2 separate Battery Packs with different capacities and different C-rates (OROVEL Card EV30) are needed.
From the description of the internal structure of the Chest-Battery part, it seems clear that Ferrari aims at filling this Chest-Battery with classical cuboid Modules supported by structural support scaffoldings. The patent says that “the different layers preferably consist of plates of metal material”.
Ferrari Battery Rear Pack structure. The plates (red) are parallel to the Rear Floor while the scafolding structures (blue) are vertical to the reference horizontal floor of the vehicle.
These plates should be parallel to the rear structure according to the patent but the scaffolding is based on a pure vertical structure meaning that the defined boxes are not perfectly perpendicular to each other. The Ferrari Patent mentions that the column structures are made from extruded tubular elements - preferably with a cylindrical section.
Reference: Ferrari Patent US 11,220,169 B2, “Electric or Hybrid Sport Car”; Inventor = Fabrizio FAVARETTO; 2022
