How Hybrid System Indicators Work

Musician Rami Jafee prepares to test drive the Ford Escape Hybrid SUV. Hybrid system indicators keep drivers of hybrid cars in the know about their fuel efficiency and driving habits.
Musician Rami Jafee prepares to test drive the Ford Escape Hybrid SUV. Hybrid system indicators keep drivers of hybrid cars in the know about their fuel efficiency and driving habits.
Vince Bucci/Getty Images

Early automobiles, ones built near the turn of the 20th century, didn't come with many extra features. Engineers were more concerned more with the practical nature of engines and other mechanical aspects -- in other words, getting a car to actually work -- so this tended to overshadow most efforts in design and usability. Most auto manufacturers were simply installing engines in light carriages and buggies, fitting bicycle wheels to each of the four corners and rolling the cars out the factory door -- without much focus on luxury. Aside from the steering wheel, the pedals and occasionally a handbrake, these early cars were essentially "horseless carriages." Actually, that's how a lot of people referred to them at the time. The dashboard was effectively void of any bells or whistles. In fact, the term "dashboard" allegedly comes from the screen people used on horse-drawn vehicles to block any water, mud or snow a horse's hooves might fling upward while "dashing."

In 1902, however, car interiors started to become a bit more helpful. The introduction of the speedometer put a gauge right near the steering wheel, allowing drivers to see just how fast they were traveling. We might take something as simple as a speedometer for granted today, but early in the car's history, this was really the only way to accurately monitor their speeds and drive safer. Since then, improvements to the car's interior have only increased, making the drive both safer and more comfortable. Now, we have clusters of indicators letting us know our speed, the engine's revolutions per minute (RPMs), the engine oil pressure, coolant temperature and even whether or not we've remembered to buckle our seat belt. We also have air-conditioning and heating systems that allow us to accurately control the interior's temperature -- sometimes in multiple zones.

With global temperatures heating up, gas prices fluctuating and drivers looking for alternatives to gasoline-only engines that give off heavy amounts of carbon emissions, many are looking toward hybrid cars -- specifically gasoline-electric hybrids -- for an environmentally and economically sound solution.

Now, hybrid cars are upping the ante by giving drivers even more information with which to work. On top of traditional instrument readouts like speed and RPMs, some hybrids are using increasingly sophisticated hybrid system indicators, which inform the green-minded commuter about important statistics like real-time fuel economy and battery levels.

So what do hybrid system indicators actually do to assist drivers? Do they simply give us statistics, or can they take their information a step further and help people become better, more efficient drivers? Find out on the next page.

Hybrid Fuel and Energy Displays

Hybrid system indicators are a big leap from old fuel gauges in terms of how much data they display.
Hybrid system indicators are a big leap from old fuel gauges in terms of how much data they display.
Justin Sullivan/Getty Images

The fuel gauge within the instrument cluster from an older gas-powered car is clearly one of the most important pieces of information a driver needs to monitor. This rather simple device works with the help of a sending unit inside the car's fuel tank. This consists of a small foam float connected to a thin metal rod, which wipes against an electrical device called a resistor as the gas level decreases. The resistor sends an electric current to the fuel gauge, and the results are displayed via the small needle every driver uses to tell whether the gas tank is full or empty. As the fuel level decreases and the float moves downward with it, the metal rod, or wiper, moves across the resistor -- the farther along it moves, the stronger the electric current is. And the stronger the electric current is, the closer to empty your tank is, too.

Newer cars use microprocessors to read the resistor and communicate this information -- hybrid cars aren't any different. Computers are behind much of how hybrid system indicators collect, calculate and display information, especially since most hybrid drivers want to know things like battery life and fuel economy in addition to how much gas is left in the tank. The main draw to hybrid system indicators is that they're multi-informational -- they present the driver with not just one or even a few pieces of information but many, many bits of valuable data. These features are typically customizable and can reflect a wide range of statistics.

Because hybrids use a combination of an electric motor and gasoline engine, the main focus of a hybrid system indicator is usually the battery level, the gas level and the dynamic between the two. Hybrids measure battery life using volt meters or computers to send the flow of amps to the display unit. The traditional fuel sender unit, along with fuel temperature sensors and more sophisticated vehicle inclination sensors, determines gas levels and sends the information to a microprocessor. This information is sent directly to the fuel display for the driver to see. The computer also continuously takes the car's average miles per gallon reading to determine how efficiently the engine is operating.

So how can all of this make you a better driver? Keep reading to find out.

How to Hypermile Using Hybrid System Indicators

Many hybrid system indicators can coach or guide drivers on fuel efficient habits.
Many hybrid system indicators can coach or guide drivers on fuel efficient habits.
Matthew Cavanaugh/Getty Images

Most hybrid system indicators on the market give the usual information, like miles per gallon and battery life. But are there intuitive and innovative ways to present the data?

On top of just giving drivers important data, many hybrid system indicators use special graphics and bright visualizations to convey a car's green features. These high quality displays are typically digital readers at the very least, but more intricate and high-tech ones are using liquid crystal display (LCD) technology to graphically illustrate the vehicle's performance. Ford's SmartGauge, for example, which it features on its Ford Fusion Hybrid, has a large speedometer in the center of its instrument cluster, but it's surrounded with bright, customizable LCD displays that give battery and fuel levels, miles per gallon and other valuable data. Depending on how efficiently you're driving, a computer-generated illustration of a leafy vine changes to reflect how "green" the car is at the moment. If you drive recklessly, like if you lean a little too heavily on the gas pedal, the leaves wither and die. If you focus more on efficient driving tactics, such as a light foot on the accelerator pedal, for instance, the leaves will grow and flourish.

This leads us to another feature of many hybrid system indicators, specifically one meant to help the owner. Depending on the system, drivers may also receive hypermiling tips from the instrument cluster, or advice on more efficient driving techniques. For instance, one of the easiest practices you, as a driver, can alter is how quickly you accelerate or decelerate -- the harder you press on the pedals, whether it's to move forward or to brake, the less efficient you're driving. Some systems will even let you know when you're accelerating or braking too hard by notifying you when you're doing it. Of course, they'll also let you know when you're driving at maximum efficiency, too.

Other major devices include Toyota's Hybrid System Indicator for the Prius, a central instrument display with a digital speedometer, fuel gauge, shift-level indicator and odometer reading, along with an LCD multi-information display panel that lets drivers know energy and fuel consumption, inside and outside temperatures and audio levels.

Honda makes use of a new feature called Eco Assist, which provides the driver with instantaneous feedback. In addition, at the end of each drive, the computer gives an "eco score" to the driver. This score indicates how efficient that particular trip was. The system keeps track of how the driver progresses and even awards various levels of eco status.

For more information about hybrid cars and other related topics, follow the links the next page.

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  • Gartman, David. "Auto Opium: A Social History of American Automobile Design." Routledge: New York, NY. June 10, 1994. (April 6, 2009) ei=gEzeSeG1O5_ItgezzOmiAQ &sa=X&oi=book_result&ct=result&resnum=3#PPP1,M1
  • "2010 Honda Insight Hybrid - Multi-Information Display (MID)." (April 6, 2009)
  • Klum, Evander. "Toyota Launches 2008 Highlander Hybrid." Aug. 23, 2007. (April 6, 2009)
  • Kur, Bob. "New dashboard gauges teach drivers to hypermile." Dec. 16, 2008. (April 6, 2009)
  • Merriam-Webster Online Dictionary. "Dashboard." 2009. (April 6, 2009)
  • Quain, John R. "Ford Fusion Hybrid's SmartGauge Display." The New York Times. April 2, 2009. (April 6, 2009)
  • "From speedometers to modern instrument clusters." Jan. 2005. (April 6, 2009)
  • Siemens VDO. "100 Years of Speedometers." Nov. 7, 2002. (April 6, 2009)
  • "2009 Toyota Prius Features." (April 6, 2009)
  • Toyota Technical Service Bulletin "T-SB-0163-08: Fuel Tank and Fuel Gauge Diagnostic Tips." Aug. 5, 2008. (April 6, 2009)
  • Vella, Matt and Reena Jana. "Ford's Green Plan to Drive Sales." Dec. 8, 2008. (April 6, 2009) 787972.htm