Lucid Air intends to redefine the approach to the electric car with an unsurpassed level of technology. Peter Rawlinson, the brand’s CEO, takes us to the heart of the electric sedan.
Presented at the end of 2016, Lucid Air intends to climb to the top of the hierarchy, whether it be automotive or electrical technology. As the successor to the company Atevia, also known by experts for the supply of Formula E batteries, Lucid has a strong expertise. Behind the project hides Peter Rawlison, a trained engineer who mainly worked at Jaguar and Lotus. But above all, he was the chief engineer to develop an electric sedan, today known as the Tesla Model S.
Now Lucid Air is a reality and coming to American roads. The ability for the sedan to make its first concrete evidence, but also to reveal most of its mysteries. It’s pretty hard to figure out where to start with Lucid, as the plumage and ramage are one, and so many innovations it is. But who says electric car, says above all traction battery. And to speak of it, nothing better than a presentation of Peter Rawlinson himself, which will make you regret not having had him as a physics-chemistry teacher, at a time when you had nothing better to do, what you had to draw cars on notebooks.
This is one of the most important parts of Lucid Air, and not least. The electrical unit is fully developed internally from scratch. It is the autonomy at the center of the specifications that determined all the technology around this battery, composed solely of cylindrical cells. What therefore resembles a vulgar radio-controlled car battery is, after extensive research, the starting point, which makes it possible for, among other things, Lucid Air to climb to the top of the curve in terms of autonomy.
Like Tesla or Rivian, Lucid therefore chooses cylindrical cells, for technical reasons but also for thermal reasons. More affordable and already integrated in a clean cabinet, they have an inherent mechanical resistance, especially in the case of thermal runaway. Lucid Motors uses 21-700 (or 2170) cells in its packages from Samsung SDI to Dream Edition and from LG Chem to the other models in the series. The mark indicates that the chemistry is different, without going into details. In both cases, however, there are 6,600 of these cells, divided into 22 modules of 300 cells each.
The reason for this pattern: Ohm’s law. A basic electrical rule, by the way, but which presents a challenge for the manufacturer. For now, the effect is the product of the resistance (expressed in ohms) and the intensity of the second. Or P = I²xR. And the more the intensity increases, the more the heat increases, causing physical losses. In order to reduce the intensity, it is therefore necessary to increase the voltage, expressed in volts, while taking into account the current requirements.
The Lucid teams have therefore chosen to combine the two types of assembly with, per. module, 10 series groups of 30 cells mounted in parallel. This therefore gives 220 cells connected in series and 30 groups in parallel, to a maximum voltage of 924 V, or 800 V depending on the nominal value that we learn from one of the EPA reports. This also makes it possible to understand the slightly smaller capacity of the cells on board the Lucid Air Grand Touring, which shows a total usable capacity of 112 kWh, against 118 kWh in the Dream Edition.
Each module has a cooling plate located on the back of the cells into which the glycol is injected. Peter Rawlinson thus explains that if the heat is distributed in several directions, it is more important axially than radially. Lateral cooling, too, although it can be effective, imposes the installation of channels between the cells, which expands the package, while at the same time making industrialization more complex. This is how the engineers decided to use the architecture of Atevia’s racing batteries by attaching the heat sinks to the back of the cells, where contact is most important.
Lucid Air will arrive in Europe in 2022
To make better use of this technical solution, the batteries are directed downwards (positive pole towards the ground) so that the plates and the heat transfer fluid form an additional firewall to ensure passenger protection in the event of a problem. . Under the modules there is a small compartment with the bottom of the cabinet to ventilate the battery. The box has side openings to allow gases to escape in case of thermal run, and once formed, the package is an integral part of the structure of Lucid Air.
With this layout, Lucid therefore had to find a solution to connect the cells to each other via the aluminum rail. An element that has itself could also be the subject of a long description. But we will confine ourselves to specifying that this process for producing this element is unprecedented, as it is directly molded with the box containing the cells. A unique and patented solution for optimizing industrialization. This is where the cells are connected by two ribbon wires, without revealing the secrets of soldering. One is wider and less resistant to reduce heat and loss. The second, thinner and more resistant, acts as a fuse in case of a problem. By comparison, Tesla uses round wire connections, which have the natural disadvantages that they increase heat and resistance. Lucid indicates that the air would lose 100 hp with this solution per. wire.
Engine: all inclusive
Lucid’s other skill in component development is none other than the engine. The brand has thus imagined one of the smallest electrical machines in the world, which also has the advantage of including the transmission and the inverter in a single and unique package. Side figures, the set weighs only 73 kg for a maximum power of 679 hp. This therefore represents a density of 9.30 hp / kg. It is almost 3.5 times better than the rear unit of the Porsche Taycan depicted in this infographic (the others are the engines of the Tesla Model 3 and Model S without being named).
Peter Rawlinson is currently less transparent in his explanations of obvious causes of industrial secrets. But with the miniaturization of the elements, by rethinking the arrangement of the magnets on the rotor and the shape of the coils in the stator, Lucid promises a denser magnetic field. A total of 24 square copper wires are braided and pressed into the stator. These Lucid-specific innovations allow the engine to develop more reluctance torque for the same amount of magnets. Lucid also confirms that if its motor uses the techno with permanent magnets, it is also possible to be freed from its natural resistance. It would thus behave like an induction motor (or almost) at the highest speeds. Especially since this machine can go up to 20,000 rpm. But no details about this process are known yet.
Back to solve the cooling problems. Because the more a wire heats up, the more resistant it is. To this, the engineers said they discovered several dead zones in the stator winding. Zones that do not ensure the conduction of electric currents and that can be used for cooling as close as possible to the wiring that physically emits heat. Cooling is logically supplied by oil. It is injected directly into the coil via the axial channel collector. A part that is the subject of several patents, both for its shape and function, and for its integration in the middle of the stator.
This mechanical unit, encapsulated in its housing, is sandwiched between the planetary gear transmission, where the teeth are patented: according to the designers, their shape has been optimized to transmit the maximum torque, while offering as little resistance as possible. The opposite is the reduction. The inverter is located above the electric machine. This device is based on MOSFETs (for Metal Oxide Semiconductor Field Effect Transistor), which optimize the efficiency of amplifying and switching circuit voltages. The system is made with silicon carbide (SiC) rather than standard silicon, more regularly connected to an IGBT system (for insulated gate bipolar transistors).
This offers many benefits in terms of cooling, volume and electrical resistance (again). But it was above all its ability to control high-frequency switching with high voltages that interested the Lucid teams. This technology acquired in Formula E and inherited from Atevia therefore makes it possible to achieve even more efficiency in the process of converting currents according to the acceleration or deceleration phases. But it is more expensive to apply.
Built-in charger: the dream box
The last piece that stands out in Lucid Air is called Wunderbox. Installed at the front, also used to absorb deformation in the event of a collision, it controls the entire 900+ V system of the electric sedan. It is through this that the AC and DC currents pass to recharge Lucid Air.
Recharging on alternating current (household plug, public terminal, etc.) takes place via the Type 2 port, with a power that can increase to 22 kW power, according to the information communicated by the European magazine (19.2 kW in level 2 in (USA)). It also has a DC charging capacity (on Mode 4 fast charging stations) that can target 350 kW maximum power. Peter Rawlinson is convinced that the power can go further, but nothing the charging network promises so much. Not even Electrify America, with which Lucid has established a commercial partnership (the sedans benefit from 3 years of free charging), but also for the development of the car.
Peter Rawlinson prefers to calculate the autonomy achieved by recharging time, this is how Lucid Air communicates its data. In AC charging, it would take 128 km of achieved autonomy per hour. At the fast terminals, 32 km per minute could be recovered or 482 km in 20 minutes. That equates to almost 60% battery, or the equivalent of 20-80%.
Among other features, the Wunderbox can convert voltage from older generation charging stations to calibrate to the car’s 900V system. It should therefore be able to correct a 400 V current at a currently inexplicable turbo power and vice versa. In addition, it is she who takes care of the reverse charging function. This is not yet efficient, but it will be able to operate a house via Lucid Connected Home (V2G) or another electric vehicle (V2V).
A new benchmark?
Lucid Air is not just a new electric car. Nor is it just another competitor to the Tesla Model S, its spiritual half-sister. It is a new reference in terms of engineering regardless of its aspects. Designed from the inside out, all elements are thought of on each other, to form a harmonious whole, as efficient and effective as possible. On paper, the promises are big.
For this, Lucid relies on more than 10 years of experience, especially in competition, and on millions of kilometers of road tests. It is six years since Lucid Air was introduced. Six years in which engineers have partially developed these technologies to earn efficiency. On the benches of the EPA, the Lucid Air Dream Edition Range (on 19-inch wheels) aims for a range of 836 km. The Grand Touring version is credited with 830 km or 754 km depending on its configuration.
It just has to prove itself on the road in our hands. Stay connected!