Electric vehicles (EVs) are automobiles powered entirely or significantly by electricity. Unlike conventional vehicles that rely solely on internal combustion engines, EVs use electric motors and motor controllers for propulsion. This provides quieter, smoother operation and substantially reduced air pollution compared to gasoline-powered vehicles.
Below we examine the key components and systems involved in EV design and manufacturing that enable sustainable personal transportation.
The drivetrain provides power to the wheels for propulsion. A typical EV drivetrain consists of:
- Traction batteries – Provide electrical energy storage
- Electric motor – Converts stored electricity into mechanical power
- Power electronics – Controls motor operation
- Transmission – Transfers torque to wheels
- Wheels/axles – Deliver driving force to road
Rechargeable lithium-ion batteries are predominantly used:
- High energy and power density
- High cycle life
- Reasonable cost
- Require sophisticated battery management system (BMS)
Battery packs contain many cells connected in series and parallel to deliver high voltage (200 to 400V) and capacity (50 to 100+ kWh). The large battery capacity provides an EV’s driving range on each charge.
Permanent magnet AC synchronous and induction motors are common choices due to their high efficiency and performance:
- Compact and lightweight
- High torque capability for acceleration
- Operate at over 90% efficiency
Motors are typically in the 50 to 150 kW continuous power range, using high density magnets and advanced control algorithms. Some EVs use multiple motors for all-wheel drive capabilities or independent torque control.
- Convert DC battery output to adjustable AC for motor
- Allows torque and speed regulation through pulse width modulation
- Facilitates regenerative braking for energy recovery
The power electronics strongly influence overall drivetrain efficiency.
A single speed gear reduction transmission is typically used:
- Maximizes efficiency by avoiding losses in a multi-gear transmission
- Simpler, more reliable, and lower cost
- Electric motor provides wide torque/speed range needed for desired performance
Some EVs use a 2-speed transmission for improved highway range and efficiency.
Vehicle Design Optimization
EVs are designed for maximum range, performance, safety and efficiency:
- Use of lightweight materials like aluminum and carbon fiber reduces mass
- Lower mass requires less energy to accelerate and climb hills
- Streamlined body shapes minimize air resistance
- Improves highway range where air drag is dominant
- Kinetic energy during braking is recovered as electricity
- Stores energy in battery rather than wasting it as heat
- Liquid heating and cooling loops optimize temperatures for batteries, motors, and power electronics
Low Rolling Resistance Tires
- Tires specifically engineered to minimize road friction
- Reduce energy lost deforming tires while driving
Careful attention to these factors maximizes the vehicle’s driving range per battery charge.
Producing EVs involves some unique processes:
Battery Module/Pack Assembly
- Individual cells closely packed together into modules
- Modules assembled and interconnected into a full battery pack
- Enclosure integrates cooling plates, monitoring electronics, and safety features
- Electric motor(s), gearbox, inverter, charger, converter, etc. assembled into a modular powertrain system
- Simplifies manufacturing by integrating components together early
Alignment of Chassis and Powertrain
- Motor and gearboxes aligned precisely to axles and wheels
- Eliminates driveline vibrations and noise
- Extensive use of aluminum and plastics instead of steel
- Carbon fiber, magnesium, and other exotic materials utilized
- Advanced joining techniques like aluminum laser welding
- Entire battery pack inserted and secured as single unit
- Simplifies assembly compared to positioning many small cells
Testing and Validation
- Extensive voak testing to ensure battery safety
- Validating vehicle range and performance specifications
- Verifying adherence to regulatory compliance
These processes aim to streamline manufacturing by designing assemblies for ease of automation, reducing part counts, and utilizing techniques tailored for EV architectures.
Battery Technology Innovations
Developing better batteries is central to making affordable, long range EVs. Key areas of battery research:
- Alternative anodes like lithium titanium oxide (LTO)
- Advanced cathodes like lithium nickel manganese cobalt oxide (NMC)
- Solid state electrolytes to replace liquid electrolytes
- Lithium sulfur and lithium air as potential high energy chemistries
- Silicon composite anodes for higher energy density
- Nickel-rich cathodes to reduce cobalt content
- Nanomaterials to shorten lithium ion diffusion pathways
- Tabless electrodes to improve thermal performance
- Dry electrode coating processes to increase energy density
- Three-dimensional electrode architectures
- Wet coating processes for thicker, more uniform electrodes
- Advanced drying techniques like freeze drying
- Roll-to-roll production for higher volumes
These innovations aim to improve battery energy density, power, durability, safety, production volume, and cost – all factors critical to widespread EV adoption.
Charging Infrastructure Growth
Convenient public and home charging options are essential to make EVs practical:
- Faster Level 2 chargers (6-20 kW) reduce charge times
- Smart charging coordinates with grid to lower costs
- Bidirectional charging allows V2G electricity flow
- DC fast chargers (50-350 kW) enable long distance travel
- Workplace charging expands opportunities
- Easy payment methods via apps, cards, automatic billing
- Universal connectors and charging standards
- Improved reliability and uptime
Widespread charging availability addresses range anxiety and improves EV satisfaction.
- Declining battery prices will reach $100/kWh threshold enabling cost parity with gas vehicles
- Faster charging rates will minimize charging times to add hundreds of miles quickly
- New learning-based battery management systems will extend range and lifetime
- Simplified drivetrain architectures will reduce manufacturing costs
- Enhanced vehicle-grid coordination will make EVs valuable grid assets
These trends will drive continued EV adoption and improvement.
Frequently Asked Questions
- What are the main components in an electric vehicle drivetrain?
The key components are the traction batteries, electric motor(s), power electronics, transmission, and wheels/axles.
- How do manufacturers optimize EVs for maximum range?
Range is extended through lightweighting, aerodynamics, regenerative braking, thermal management, and low rolling resistance tires.
- What manufacturing processes are unique to EVs?
Key EV manufacturing processes include battery assembly, powertrain integration, precision motor-wheel alignment, lightweight material fabrication, and battery installation.
- What battery innovations are being worked on for EVs?
Important areas of battery research are new chemistries, advanced active materials, innovative cell designs, and improved manufacturing processes.
- Why is public charging infrastructure so important for EVs?
Convenient and plentiful public charging enables long distance travel and assures drivers they can charge when needed, reducing range anxiety.