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How Hybrids Work:
Hybrid-Electric Vehicles (HEV)

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Basics to a Hybrid-Electric System

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Alex Steele


2010 Toyota Prius Hybrid
2010 Toyota Prius Hybrid

What is a Hybrid-Electric Vehicle? As gas prices climb, we hear more and more about the latest automotive alternative. A lot of prospective hybrid buyers desire improved fuel economy, others value cleaner emissions and others just have to have one. Development and production of hybrid vehicles by automakers is on the upswing. But how does this new technology work?


Hybrid Fundamentals:


A hybrid car, truck or SUV uses more than one means of propulsion -- in this case, an internal combustion engine combined with an electric motor.


As opposed to plugging your car into an electrical outlet (we'll get to that later), a hybrid-electric vehicle (HEV) uses a generator to charge a high-power battery. The generator is driven by two sources of rotational force. One is the conventional internal combustion engine, which keeps the vehicle electrically self-sufficient, and the other is a process referred to as "regenerative braking".


Cars and light-duty trucks use a hydraulic braking system which applies pressure at the brake pads or shoes, which contact the brake rotor or drum, respectively. This controlled friction slows the vehicle while wearing down the brake linings and disbursing heat. "Engine braking" is also used to aid in deceleration. This technique employs engine compression when downshifting. Both braking processes convert kinetic energy (motion) into heat (another form of energy), which is unused and discharged into the atmosphere.


Regenerative braking works in concert with standard brakes. When driving an HEV, upon initial depression of the brake pedal, the generator applies resistance to the drivetrain. This resistance slows the vehicle prior to the conventional brakes kicking in. A portion of the kinetic energy, which was previously wasted as heat, now rotates a generator and charges a battery, in turn powering an electric motor. The electric motor then assists the internal combustion engine, therefore transforming a newly harnessed source of power into additional miles per gallon and a reduced production of harmful emissions.


The HEV's onboard computer coordinates the system. Upon deceleration it activates regenerative braking to produce electricity. When that's not enough, engine power is directed to drive the generator and sufficiently charge the battery. The hybrid system also has the ability to shut off the engine while the vehicle is stopped, followed by an automatic restart, eliminating unnecessary fuel consumption at idle. Due to the high-torque characteristics of an electric motor, it's used more at low speeds, while the gas engine does most of the work on the highway, resulting in exceptionally high miles per gallon in city driving.



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24 Nov 2015, 23:14
LOL. It is funny how Japanese cars waited for Germans to come out with something hybrid but since Europe is all about small diesel engines, the Germans didn't really care for hybrids. Just now Japs are bringing hybrids and most? of them were failures. Actually first the brought electric but that failed totally so now its hybrids. But Germans if they don't want to loose american pie will have to bring hybrids in. Perhaps they could copy Japs for a change.
23 Jul 2014, 14:16
Well, to take your last point first hybrids are really nothing but a marketing gimmick. There's nothing "wrong" with them they do reduce fuel consumption. It's just a ridiculously expensive way to do it when you can build cheaper cars that get just as good mileage with efficient gasoline engines.As for the future here's my estimate: electric. The reasons are basically simple; alternative fuel cars would (based on what we know) be either biofuels or hydrogen. The first is workable but there's no way for us to produce that much biofuel without causing massive impact on the ecology worldwide. And, unless we develop some very innovative technology that isn't in the offing, it is NOT carbon neutral though it does reduce the "carbon footprint" considerably.Hydrogen presents technical problems ones that will take years to solve. Mainly this involves how to store enough hydrogen on a car to give it a decent range. also, hydrogen is currently obtained from oil. The alternative electrolysis could become cost effective. But to use electricity to break down water for its hydrogen you have to have to produce the electricity first.My guess-when we reach the point of producing that much electricity without using oil or coal to do it (by solar power, for instance) and can do it cost-effectively you might as well use that electricity to power electric cars. We already know how to build them, with enough range for urban driving and short trips and do so at reasonable cost. Going to hydrogen would just be an expensive complication.The real key we need is large scale cost-effective alternative means of generating the electricity in the first place. But the technology for that ( or technologies, rather there are several) are either already working (wind, for example) or on the verge of becoming highly competitive such as new tidal power and solar array technologies now in development).


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