Teardown: Unpacking the Lucid Motors Battery Pack
Pulling apart a Lucid battery pack provides insights into traction battery design.
The traction battery pack design is one of the keys to building an electric vehicle (EV) with long-range and quick charging.
Lucid Air Sapphire. Image courtesy of Lucid Motors
Because an EV battery makes up as much as half the cost of the vehicle, components that are easy to manufacture and assemble can reduce the EV’s overall cost. Traction batteries contain large amounts of electrical energy in a relatively small space, so the safety and protection of the battery cells are a major consideration.
Types of Battery Cells
EV battery cells come in three types.
As the name implies, pouch cells contain the electrodes and electrolytes in a flexible polymer bag that the battery pack structure must support.
Prismatic cells are similar to pouch cells but use a hard plastic shell to contain the cell components.
Cylindrical cells are similar in concept to the AA batteries most people are familiar with but are usually larger in diameter and length.
Although each type has advantages, cylindrical cells are becoming more popular among EV makers.
Cylindrical Cell Benefits and Challenges
Packaging cylindrical cells presents both challenges and advantages. It is advantageous for the traction battery to have the highest energy density possible to increase EV range, resulting from placing the individual cells as close together as possible.
When cylindrical cells are packed together, there remains space between the cells, reducing the energy density of the pack. The spaces are not all bad, however, as they allow cooling of the individual cells, either through airflow or the passing of liquid cooling media around the cells.
Tearing Down the Lucid EV Battery Pack
Lucid Motors builds luxury electric sports cars and grand touring cars at its Arizona manufacturing plant. The product lineup ranges from the Lucid Air Pure with 480-horsepower and a 410-mile range for $82.400 to the 1,234-horsepower Air Sapphire with a range of 427 miles and an eye-watering $249,000 price tag. In between, the Air Grand Touring provides a 516-mile range at $125,600 retail.
Although the goals of safety, high energy density, and low cost are similar for all EV manufacturers, how those goals are realized differs. Munro & Associates examined the battery pack from a Lucid Sapphire EV. Munro’s findings can provide insights into how EV battery engineers create traction battery packs.
A Lucid Motors battery pack. Image used courtesy of Lucid Motors
Munro examined the 22-module traction battery pack from a Lucid Air Grand Touring model. The base level of the battery pack contains 19 modules, while three additional modules are located on a second level along with the power distribution level. Lucid uses between 18 and 22 modules in its traction battery packs, depending on the model and trim level. The 18-module pack has 92 kilowatt-hours (kWh) capacity, while the Grand Touring pack with 22 modules has a capacity of 112 kWh. The Sapphire model pack has 22 modules, but a change in battery cell chemistry provides 118 kWh.
Lucid uses exclusively 21700 cylindrical cells in its traction battery packs. This cell is 21 millimeters (mm) in diameter and 70 mm long and is larger and has more capacity than previous generation 18650 (18 mm diameter, 65 mm long) cells. There are 300 cells in each Lucid module. Hence, the 22 module models contain 6,600 individual cylindrical cells, each of which must be connected in the proper way to provide the required voltage and current output and monitored for voltage and temperature. Each module is made up of an injection-molded plastic case that contains ten groups of 30 cells that are separated by thermos-formed mica sheets. The cells are free-floating in the modules and, unlike other packs, do not have a potting system to hold the individual cells in place.
Image used courtesy of Munro & Associates
On top of each module also sits an aluminum cooling plate that assists the pack’s liquid cooling system to help keep temperatures under control. Nylon hoses provide a feed of cooling liquid to and away from the pack.
The EV Battery Pack’s Composite Base
The Lucid traction battery pack sits beneath the vehicle, extending from the front of the car to the rear. The modules are mounted to a base made from fiberglass-reinforced epoxy that acts as a floor for the pack and protects it from road debris and other impacts. At the rear, mid-pack, and front of the base, aluminum castings hold the modules in place. Side sills and additional supports are machine aluminum extrusions. Structural adhesives attach the castings and extrusions to the composite base. Three separate lids are made from sheet molding compound (SMC), a plastic material that covers the top side of the base and protects the modules from above.
Serviceability is not part of the strategy that Lucid is employing for its traction battery packs, according to the Munro team. The extensive use of structural adhesives, including on the plastic SMC top covers, makes disassembly nearly impossible without damaging or destroying parts and components.
The Verdict on the Lucid Motors Battery Pack
Every EV manufacturer has its own way of building its traction battery packs. Although Lucid Motors has its way of doing things, the result must be a battery pack that provides the highest energy density possible for maximum range, a design that facilitates easy assembly for reduced costs, and a reliable package that offers a decade or more of service without requiring any maintenance – all while ensuring the pack is safe and well-protected from road debris and hazards. Munro concluded that the Lucid Motors battery pack was impressive and cleverly designed to meet these requirements.