How Hybrid Cars Work

How Conventional Cars Work

1. The engine burns gasoline to produce power and to generate the electricity needed to run the car’s radio, air conditioner, and other electronics.
2. The engine turns the transmission.
3. The transmission turns the wheels.
4. The turning wheels make the car move.

Hybrid Cars: Gasoline and Electric

The Electric Motor

• The electric motor powers the transmission: The transmission turns the car’s wheels, so whatever powers the transmission makes the car go. In some hybrid cars, the electric motor powers the transmission on its own when the car is at low speeds. At these speeds, the gas-powered engine contributes no power and uses no gas.
• The electric motor assists the engine: When the electric motor isn’t powering the car by itself, it adds torque, which assists the engine in turning the transmission. Hybrid cars have smaller engines than gasoline-only cars, since the motor works alongside the engine to power the transmission. The combined operation of the smaller engine and the electric motor means that hybrid cars need less gasoline than conventional cars to spin their wheels with the same amount of power.
• The electric motor turns off and restarts the engine: Conventional cars use gasoline when they idle, since the engine continues to run when the car is stopped. Hybrid cars don’t use gasoline when they idle. The motor on a hybrid car acts as a starter that turns the engine on when it’s needed and off when it’s not needed (for example, when stopped at a red light). The motor also keeps the air conditioning and other electronics on whenever the car is operating.
• The electric motor recharges the batteries: The electric motor can also generate its own power by recharging its batteries during normal vehicle operation.

The Batteries

• They don’t need to be plugged in: One of the biggest misconceptions about hybrid cars is that they need to be plugged in to recharge the batteries—they don’t. Today’s hybrid cars recharge their batteries while driving, with no cords or plugs.
• They reuse energy that conventional cars waste: When a driver applies the brakes to stop the car, the brakes generate heat from friction. That heat provides an energy source, which hybrid cars capture to recharge their batteries. This process is called regenerative braking.
• They last through the life of the car: Most rechargeable batteries—such as the types used in cell phones or laptops—last for only a few years before their ability to recharge diminishes and they need to be replaced. But hybrid car batteries don’t lose their ability to recharge, in part because they’re never completely full or empty. The batteries maintain an optimal charge of about halfway full, making them last as long as—or longer than—the typical life of the car.