WEBVTT - How does a hybrid car work?

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<v Speaker 1>Welcome to Brainstuff from how stuff works dot com where

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<v Speaker 1>smart Happens. Hi. I'm Marshall Brain with today's question, how

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<v Speaker 1>does a hybrid car work? We're all familiar with gasoline

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<v Speaker 1>powered cars, and most people have heard about our scene

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<v Speaker 1>electric cars. A hybrid car is a combination of the two.

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<v Speaker 1>Hybrid vehicle contains both a gasoline engine and an electric

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<v Speaker 1>motor in an attempt to get the best of both worlds.

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<v Speaker 1>The best way to understand the advantages of a hybrid

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<v Speaker 1>vehicle is to think about a car traveling down a

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<v Speaker 1>highway at the postage speed on level ground. In this case,

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<v Speaker 1>the engine is doing three things. First, it's overcoming rolling

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<v Speaker 1>resistance in the drivetrain. Second, it's overcoming air resistance, and

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<v Speaker 1>third it's powering accessories like the alternator and the air conditioner.

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<v Speaker 1>The engine might need to produce no more than twenty

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<v Speaker 1>horse power to carry this load. The reason why cars

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<v Speaker 1>have a hundred or two hundred or three hundred horsepower

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<v Speaker 1>engines is to handle acceleration from a standing stop, as

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<v Speaker 1>well as for passing and hill climbing. We only use

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<v Speaker 1>the maximum horsepower rating for one percent of the driving time.

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<v Speaker 1>The rest of the time we are carrying around the

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<v Speaker 1>weight and friction of that much larger engine, and that

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<v Speaker 1>wastes a lot of energy. In a pure hybrid vehicle,

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<v Speaker 1>you have a complete electric car. It includes an electric

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<v Speaker 1>motor to provide power to the wheels, as well as

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<v Speaker 1>batteries to supply the motor with electricity. Then you have

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<v Speaker 1>a completely separate gasoline engine powering a generator. The engine

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<v Speaker 1>is small, perhaps only twenty horsepower, and it's designed to

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<v Speaker 1>run it just one speed for maximum efficiency. The purpose

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<v Speaker 1>of this small, efficient engine is to provide enough power

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<v Speaker 1>for the car at its cruising speed. During times of acceleration,

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<v Speaker 1>the batteries provide the extra power necessary. When the car

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<v Speaker 1>is decelerating or standing still, the batteries recharge. This sort

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<v Speaker 1>of hybrid car is essentially an electric car with a

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<v Speaker 1>built in recharger for longer range. The advantage is that

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<v Speaker 1>the small, efficient gasoline engine gets great mileage. The only

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<v Speaker 1>problem with this traditional hybrid car is the weight. The

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<v Speaker 1>car has to carry the weight of the electric motor,

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<v Speaker 1>the generator, the gasoline engine, and the batteries. You don't

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<v Speaker 1>need as many batteries as a pure electric car, so

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<v Speaker 1>that saves some weight, but a full size electric motor

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<v Speaker 1>plus a ten kilowatt generator can weigh several hundred pounds.

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<v Speaker 1>Most hybrid vehicles, therefore, try to strike a compromise. They

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<v Speaker 1>use a larger gasoline engine that's connected directly to the

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<v Speaker 1>drive train, along with a smaller electric motor attached to

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<v Speaker 1>the engine or the transmission. The gasoline engine provides most

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<v Speaker 1>of the car's power, with the electric motor adding extra

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<v Speaker 1>power is needed for acceleration. Because the electric motor can

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<v Speaker 1>double as a generator during breaking and only has to

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<v Speaker 1>run part of the time, it can be extremely light.

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<v Speaker 1>The disadvantage of this approach is that the gasoline engine

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<v Speaker 1>must run at varying speeds, which reduces its efficiency. For

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