Hybrids Explained

Hybrids Explained

Defining the term ‘hybrid’ as it relates to the automotive world.

When you hear the word “hybrid,” what comes to mind?

A Toyota Prius? The Prius is the most common and distinctive hybrid on the road today. But there are other hybrids, too, such as the Honda Insight, Civic and Accord, Nissan Altima hybrid, Toyota Camry and Highlander hybrids, Ford Escape hybrid, Lexus RX400H and GS450H hybrids, Saturn Vue hybrid, and the 2009 Chevy Malibu, Chevy Tahoe, GMC Yukon and Silverdo hybrids.

There aren’t a lot of hybrids on the road (only about 1.4 million to date), but their numbers are growing. Depending on what happens with fuel prices, the economy and the financial balance sheets of the automakers, hybrid sales could grow to as much as 20 to 25 percent of new car and truck sales within a few short years.
So what exactly is a hybrid? The word itself means the offspring or combining of two different things, be it plants, animals or technologies. By combining the two, you hopefully get the best attributes of both. With respect to automobiles, a hybrid vehicle is one that uses two different power sources for locomotion. Right now, that means using a high-voltage battery and electric motor(s) to augment the vehicle’s gasoline engine. In the future, it could mean using any combination of battery power, fuel cell technology, alternative fuel spark ignition or diesel engines, or even compressed air or high-inertia flywheels to power vehicles.

For model year 2010, Chevrolet says it will offer the first mass-produced “extended range electric vehicle” (E-REV), which is essentially a “plug-in” hybrid. The car will be called the “Volt.” Inside will be a lithium ion battery that is recharged by plugging the car into a conventional 110V electrical outlet. This will give the car a range of up to 40 miles on electric power alone, which should be adequate for the typical commuter. The car will also have a small gasoline engine that takes over when the battery is low, and to recharge the battery. Chevrolet says future models of the Volt may replace the gasoline engine with a diesel engine or even a hydrogen fuel cell.
The basic idea behind a hybrid vehicle is to use supplemental battery power so the gasoline engine runs less. The less the gasoline engine runs, the less fuel the engine burns and the better overall fuel economy the vehicle delivers. Running the engine less also reduces pollution and CO2 emissions, which helps reduce global warming.

The current approach with hybrids is to shut the engine off completely when a vehicle has stopped for more than a few seconds. This saves the fuel that would otherwise be wasted when the engine is idling and getting zero miles per gallon.

When the driver steps on the gas pedal to go after the light turns green, a “full” hybrid such as the Toyota Prius, then uses battery power alone to start the vehicle moving. The vehicle will continue to run on battery power alone until it hits a speed of 12 to 25 mph. At this point — which depends how hard the driver is pressing on the gas pedal and how fast the vehicle is accelerating — the engine restarts and takes over. During hard acceleration, the vehicle may use both battery power and engine power to maximize performance.

With a “mild” hybrid vehicle such as a Saturn Vue or Honda Civic hybrid, there is no full battery mode of operation. Mild hybrids only have a start/stop system that turns the engine off when the vehicle comes to a halt. The mild hybrid system then restarts the engine as soon as the driver steps on the gas. The starter/alternator may also provide an added boost during hard acceleration. This is called “electronic supercharging” because the extra power assist only occurs when accelerating quickly, when climbing a steep grade or when towing. The added kick is the equivalent of an extra 20 to 30 horsepower while it lasts.

In the Saturn Vue, for example, the mild hybrid system uses a combination starter/alternator that is belt-driven and bolts to the side of the engine. There is a high-voltage battery in the back for starting the engine and adding electronic boost, but the battery does not have the capacity or voltage of a full hybrid battery like that in a Prius. Even so, the high voltage can still be dangerous and requires certain precautions when servicing or repairing the vehicle.

Adding a supplemental battery start/stop system and a full electric driving mode up to a certain speed can make a substantial difference in a vehicle’s fuel economy. A Prius will typically get anywhere from 42 to 60 mpg in the city, depending on how it is driven. On the highway, battery power is not used so there is not much benefit in cruising fuel economy. But in stop-and-go traffic, and when accelerating (which uses the most energy), a hybrid can boost fuel economy 25 to 50 percent.

In spite of all the improvements that have been made in gasoline engines over the years, they are still not very energy efficient. They waste up to two-thirds of the heat energy produced by every drop of gasoline they burn. Most of the waste heat either goes out the tailpipe or is absorbed by the cooling system. Diesel engines are 20 to 30 percent more efficient than gasoline engines, but also waste a lot of heat energy. So engineers see hybridization with supplemental battery power as one way to significantly improve fuel efficiency without making drastic changes in engine technology (at least for now). Down the road, fuel cells may eventually replace gasoline and diesel engines entirely. But there are still a lot of questions about where all the hydrogen that would be needed to power large numbers of vehicles would come from, how it would be stored and distributed, and how much it might cost. Until those problems are sorted out, hybrids appear to be the best short-term solution to reducing fuel consumption and emissions.
Though most people think hybrid technology is relatively new (the first Prius went on sale in Japan in 1997, and was brought to the U.S market in 2001), it actually dates back to the early days of automotive history. In 1905, an inventor named H. Piper applied for a patent for a hybrid vehicle powered by an electric motor and a gasoline engine. In France, the Paris Electric Car Co. built a number of electric hybrid vehicles from 1897 to 1907.

About the same time, Ferdinand Porsche designed cars for the Lohner Car Co. in Austria that had electric motors inside the wheel hubs. The gasoline engine drove a generator to power the motors, eliminating the need for a conventional transmission (this is the same setup used today in train locomotives). Other automakers that produced hybrid cars during this period were General Electric, the Galt Motor Co., Siemens-Schuckert, Woods Motor Vehicle Co., and the Walker Vehicle Co.

These early hybrids were very primitive and crude compared to today’s hybrids, but the basic concept was similar. The two main reasons why hybrids never caught on and became mainstream was because engines improved and gas was relatively cheap. Higher compression ratios, overhead valve cylinder heads and other improvements meant gasoline engines could deliver good performance and fuel economy without expensive add-ons. And as long as gasoline was relatively cheap and readily available, fuel economy wasn’t such a big deal.

Then came the oil embargo of the 1970s, soaring fuel prices and the first major “energy crisis” to confront our nation. Once again automotive engineers looked at hybrid technology as a way to improve fuel economy, but opted instead to downsize vehicles and switch to smaller engines (remember the Chrysler K-Cars and Ford Escort?) Import car sales skyrocketed and the Big Three Detroit automakers began to lose market share.

When fuel prices came back down, cars began to bulk back up. By the 1990s, many Americans were driving large SUVs instead of passenger cars. Then gasoline prices started to rise again, and some people began to look around for more fuel-efficient options. The first was actually the Honda Insight, which went on sale in 2000, followed by the Prius in 2001. But these were limited production vehicles, built in relatively small numbers. And many people were leery of the new, unproven technology.

As time went on, people became more familiar with hybrid cars, and realized the advantages they offered. The “green” movement also went mainstream, and people became more interested in driving vehicles that made a statement about being fuel efficient and environmentally friendly. When gas prices soared to more than $4 a gallon in 2008, people were standing in line at dealerships to buy hybrid cars at full list price (plus whatever the dealers could tack on for added profit). The dealers couldn’t give away their big SUVs.

Now, most of the world’s automakers have climbed aboard the hybrid bandwagon and have introduced (or will be introducing) new hybrid models to satisfy the public demand. Production numbers will continue to be limited, though, primarily because of bottlenecks in battery manufacturing. Toyota is building a third hybrid battery plant in Japan, and the domestic automakers have pooled their efforts to develop next generation batteries that promise to be even better than today’s hybrid batteries.
Unfortunately, hybrid technology is not easy or cheap. It reportedly adds $2,500 to $3,000 or more to the sticker price of the vehicle. Consequently, the payback depends on the price of gasoline, the mileage the vehicle gets, and how many miles the vehicle is driven. When gas was more than $4 a gallon, the payback was fairly quick. But if gas continues to sell for less than $2 a gallon, the payback will take twice as long.
Hybrid technology is expensive because it adds a lot of hardware to the vehicle.

A full hybrid requires a large high-voltage battery, control electronics and one or more electric motors incorporated into the transmission or flywheel. A mild hybrid is somewhat less expensive because it uses a smaller battery and a combination starter/alternator, but it still adds significant cost to the vehicle.

Some people question the reliability of the high-voltage battery and powertrain in hybrid vehicles. So far, most hybrids have proven to be just as reliable as any other vehicle, and warranty issues have been nil. All cars have their quirks, and hybrids are no exception.

There have been some incidents of hybrids suddenly shutting down due to electronic glitches in their control modules. But the high-voltage batteries have been rock solid reliable (except for the early production Saturn Vue hybrids, which were recalled to replace some bad batteries).

Most vehicle manufacturers are offering extended warranties on the hybrid components. The first-generation Toyota Prius models are covered by an eight-year, 100,000-mile warranty.

On the newer Prius models, Toyota has extended the hybrid warranty to 10 years or 150,000 miles. Similar coverage is offered by most of the other vehicle manufacturers on their hybrid models.

Hybrid technology does add a lot of complexity to a vehicle. Because of this, many independent repair shops feel they are not trained or equipped to work on hybrids. But this situation is improving as hybrid training becomes more available, and more technicians get up-to-speed on the new technology.
The main concern with hybrid vehicles is the high-voltage battery and electronics. Depending on the application, the battery may be packing anywhere from 174 volts to more than 300 volts.

That’s enough to electrocute an unwary technician or rescue worker should the vehicle be involved in an accident. Fortunately, many safeguards are built into hybrid vehicles to minimize the danger.

The high-voltage battery is buried in the back of most hybrids under carpeting and panels, making access rather difficult. The high-voltage circuits are heavily insulated and shielded, and are usually color-coded orange (or blue in the case of mild hybrids with 42 volt systems). The hybrid battery is automatically isolated from the electrical system if the control module detects a short to ground, or if any air bags are deployed in a collision.

Technicians are required to wear insulated rubber gloves that can withstand 1,000 volts, and to disconnect the high-voltage battery before doing any repairs that involve components in the hybrid system.

This is not necessary when doing other repairs such as brake work, engine maintenance, etc. Using insulated tools (wrenches, ratchet handles, screwdrivers, pliers) when working on hybrids is also recommended. Of course, once the battery is disconnected there is no danger — assuming the technician waits up to 30 minutes for the high-voltage capacitors inside the inverter to discharge before doing any work that involves the hybrid electronics.

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