How Does the Hybrid Synergy Drive Work?

February 10, 2012

Hybrid vehicles are the subject of ever increasing popularity, thanks in part to their complex hybrid synergy drive systems. These systems, pioneered by the Toyota Prius, use a combination of gasoline and electric engines in tandem with a continuously variable transmission to give superior fuel economy and power delivery over a wide range of speeds and conditions. Hybrid Synergy Drive is a drive-by-wire system with no mechanical connection between the engine controls and the engine itself, and as such uses solely electrical signals to determine drive train output.

Overview of Operation

In a conventional internal combustion engine, a battery is used to power accessories while the engine is turned off. As well as in combination with a starter motor, which is used for starting purposes only. An alternator powers accessories and recharges the battery while the engine is in use, and the engine itself is the focus of the vehicle's motivation. In a Hybrid Synergy Drive or HSD power train, the transmission, alternator and starter motor are replaced with a pair of powerful electric motors which generate approximately 60hp, and can work either by themselves or in unison with a conventional internal combustion engine as needed. Power distribution is controlled through a combination of mechanical power splitter, and computer controlled shunts while the motors themselves are powered by a battery pack and used for start up, low speed driving and acceleration.

Internal Combustion or Electric Power on Demand

While the internal combustion engine itself may not even be active during start up, it may be used on demand for higher road speeds, increased acceleration, or to aid in increased battery charging. When the aid of the internal combustion engine is required, one of the electric motors may be used as a starter. When the aid of the gasoline engine is no longer required, the engine itself may be turned off as needed, with load shifted in full to the electric motors. This allows a hybrid engine configuration to achieve superior fuel economy without any holes of lags in power delivery.

Regenerative Braking

In convention vehicles, braking duties are handled in full by the braking system. In the case of a vehicle equipped with hybrid synergy drive, the bulk of braking is actually handled by the same electric motors that power the vehicle. The initial travel of the brake pedal engages the motors into generator mode, which converts forward momentum into electrical current. This in turn is used to both slow the vehicle and recharge the vehicle's battery packs simultaneously. This both eliminates the need for conventional battery charging methods and greatly extends the life of traditionally equipped braking components.

Hybrid Synergy Drive equipped vehicles have managed to directly address many of the downsides found in both gasoline powered and electrically power drive trains alike, by combining their strengths into one versatile package. It is through this unique versatility in operation that hybrid technologies have become so successful compared to their fully electrically powered counterparts. Also, it's one of the main reasons why this technology may become a staple in the future of automotive technology.

Related Questions and Answers

What are the Best Sources for Information about Hybrid Vehicles?

Information about hybrid vehicles can be obtained from several different sources. Vehicle manufacturers will have a considerable amount of information on the vehicles they make. Additionally, side by side comparisons can be made between standard vehicles and hybrids, or between hybrid models. is another good source for information. There are also some sites that are specialized in green technology, and more specifically, alternative fuel and hybrid vehicles. One of these sites is, and the other is AE Hybrid Cars.

Does it Really Cost More to Build a Hybrid Car than Normal Gasoline Vehicles?

It costs more to build a hybrid car than it does to build a standard vehicle. Hybrid vehicles contain multiple electric motors, a battery pack, and the supportive electronics to use this extra equipment. The battery pack is specialized and typically around 288 volts, which is significantly more than a standard 12-volt battery. The electric motors are large and expensive. After all, they have enough power to propel the vehicle up to 25 miles per hour without the use of the fuel-burning engine. What is more, the computer and electronics are responsible for charging the battery pack and determining when to use the electric motor or fuel-burning engine.

Do Hybrid Cars Really Put Out Less Pollution?

Hybrid cars' pollution is considerably less than that of their standard fuel burning engine counterparts. A fuel burning engine is used exclusively to propel the vehicle, in standard type automobiles. However, hybrid vehicles use both a fuel burning engine and electric motors. At low speeds, and stop and go driving, the hybrid uses the electric motor exclusively to move the vehicle. Indeed, the fuel burning engine will not even be started until the vehicle sustains speeds of 25 miles per hour or more. Because a portion of the work is performed by electric motors, the hybrid vehicle's emissions are lower.

How Much is a Hybrid Car on Average?

You are probably wondering: 'how much is a hybrid car?' on average. With so many vehicle manufacturers producing hybrid vehicles, the costs are very close to being comparable to standard vehicles. Side-by-side comparisons show hybrids to be less polluting and about twice as efficient on fuel. Although they typically cost from $4,000 to $20,000 more than standard cars, a hybrid can pay for the cost difference in fuel savings over the life of the car loan. Indeed, just consider how much fuel savings there would be over the life of the vehicle. Expect to pay approximately $30,000 for an average mid-sized vehicle.

Is the Market for Hybrid Cars Growing?

The market for hybrid cars is growing mostly due to the high cost of fuel. In addition to the costs of fuel, environmental concerns have also played a major role in the proliferation of hybrid vehicles. Even though we are in depressed economic times, more people are willing to pay the little extra to purchase a hybrid vehicle, because they will be saving money on fuel in the end. Indeed, hybrid vehicles also use less mechanical parts in their construction, making them more reliable and cost effective to operate.