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An inverter changes the battery's DC power into AC power. An inverter changes the battery's DC power into AC power for the electric motor and the generator's AC to DC to recharge the battery.
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Toyota Prius battery pack
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It also extends the life of the battery by maintaining the correct charge and adjusts the regenerative braking power. When you slow down or brake in the Prius, the kinetic energy from wheel motion generally dissipated as heat, is converted to electric current and stored in the battery.
Increased fuel efficiency is significantly enhanced by this process that accounts for around 20% of the energy used by the Prius. Additionally, the transmission helps recharge the battery when your foot is off the accelerator, mostly in a coasting or downhill mode. There's also the car's computer that monitors the amount of charge in the battery, keeping it between 30-70% capacity, and allowing the battery to last several hundred thousand miles - generally the life of the vehicle.
The Prius's electronic control system adjusts to driving conditions by selecting which engine to use, thereby increasing power output and lower fuel usage. The transmission in the Prius has only one gear set - no clutch, starter, alternator or torque convertor - and easily adjusts the function of the gas engine, the electric motor and the generator to driving situations. The planetary gear power-split device in the transmission allots power from the IC engine to the drivetrain and generator, which produces electrical power that charges the battery, drives the electric motor and serves as the starter for the gas engine. The surprising effect is a quiet, seamless system. The car is especially quiet while idling when the IC engine shuts off.
For 2004, the latest model of the Prius will be the first Toyota to be outfitted with a new high-voltage/high-power Hybrid Synergy Drive powertrain, which can run on either or both gas and electric motors. Of course, while running on electricity only, fuel economy improves and toxic emissions are reduced. The major improvement in the new system is the duration of electric-powered driving and improved power and performance derived from the electric motor, which has been increased by 50%. A 15% rise in fuel efficiency is also expected to the mid-50 mpg range for combined city and highway driving.
The Honda Civic hybrid, the primary competitor of the Prius, employs the technology of its predecessor, the Insight, in a more conventional-looking vehicle. Other than a few design distinctions, the Civic hybrid preserves the look of the popular non-hybrid four-door Civic sedan. Under the hood, however, is where the differences exist. A cover under the engine and rear floor improves aerodynamics and subsequently fuel economy, and a cable runs from the transmission housing to connect the electric motor stashed between the transmission and the gas engine to the battery control at the rear. The Civic hybrid's electric components are more compact than the Insight's and are lodged between the back of the rear seat at the front of the trunk, accessible through a trunk panel.
The transmission in the Civic hybrid has variable gear ratios supplied by belts that run between moveable pulley wheels, offering a smooth ride and increased fuel efficiency. One unusual experience happens when accelerating hard - the engine speeds up and the transmission seems to lag or slip a clutch. Then the engine revolutions slow as the ratio changes while the car is accelerating. Another oddity occurs at idling - stopped at traffic, the engine shuts off to save fuel and when you begin to accelerate, there's no hesitation. Car owners will enjoy the overall smooth ride and exceptional steering due to an electrically-operated rack-and-pinion steering system.
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