Basics of Start-Stop system and Micro Hybrid

Basics of Start-Stop system and Micro Hybrid

 

Start-Stop System

 

The Start-stop system is based on an intelligent combination of engine, brake, and battery management, which stops the internal-combustion engine when the vehicle is at a standstill in a traffic jam or at a red light. As soon as the driver presses the clutch pedal, the system automatically restarts the engine. The electronics ensure that the driver can save fuel and cut CO₂ emissions without compromising on convenience.

 

The start-stop system is also known as Stop-Start or Idle Stop and Go system. This feature is present in hybrid electric vehicles, but has also appeared in vehicles which lack a hybrid electric powertrain. For non-electric vehicles fuel economy gains from this technology are typically in the range of 5 to 10 percent.

 

How Start-Stop System Works:

 

Note: The working of Start-stop System will be handled in the next part of the article. It requires basic understanding of automotive systems.

 

Systems with Start-Stop

 

1.) Micro Hybrid

 

A Micro Hybrid is a conventional fossil-fuel vehicles (diesel/gasoline etc.) with Start-stop system.

 

The Micro hybrids are fitted with an Internal Combustion Engine (ICE) and a large electric machine. These vehicles allow the engine to be turned off whenever the car is coasting, braking, or stopped, yet restart quickly when the clutch or accelerator is pressed. The basic propulsion is via the ICE but the electric machine will help start the vehicle.

 

A Micro Hybrid system the electric motor doesn't add thrust to the combustion engine. In other words it can not power assist to the ICE.

 

 

2.) Mild Hybrids

 

In a Mild hybrid the internal-combustion engine is assisted by an electric motor, which delivers additional drive power and braking power in different operating states. There is a small difference between Micro and Mild Hybrids. In mild Hybrids the electric motor adds thrust to the combustion engine or does power assistance to the combustion engine. However the electric motor cannot turn the drive wheels by itself. The fuel advantage for mild hybrid is slightly better then Micro Hybrid. They also implement regenerative braking to generate power.

 

3.) Full Hybrid

 

In a full hybrid internal combustion engine is combined with one (or two) electric motor(s). In additional to running on the internal-combustion engine and being assisted by the electric motor, it also allows for purely electric driving.

 

Note:

- A Hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles, which combine an internal combustion engine and one or more electric motors. In this article hybrid vehicles term refers to hybrid electric vehicles (HEVs) unless otherwise specified.

- There are more variants in Hybrid Electric vehicle wherein Start-Stop system is used which is out of scope for this article.

 

 

Advantages of Micro Hybrid as compared to Conventional system

 

- The start-stop system reduces the amount of time the engine spends idling, thereby improving fuel economy and reducing emissions.

- Fuel economy gains from this technology are typically in the range of 5 to 10 percent

- The CO₂ reduction is almost the same as the gain from Fuel Economy.

- Implementation cost is not very high (generally in range $300-$400)

- In combination with Modern Spark ignition engine, a warm start uses as much fuel as is required for 0.7 seconds of idling. So every stop more then 0.7 seconds pays off.

- Generally it implements regenerative braking which improves the energy efficiency of vehicle.

 

Disadvantage of Micro Hybrid System

 

-         Fuel Saving is not as good as Mild or full Hybrid

-         Some vehicle functions may not run when engine is Off (Air conditioner etc)

-         Even though the implementation is cheap, the vehicle manufacturer may charge huge amount for vehicles with Start-Stop systems

 

Regenerative Braking

 

In a traditional braking system, brake pads produce friction with the brake rotors to slow or stop the vehicle. Additional friction is produced between the slowed wheels and the surface of the road. This friction turns the car's kinetic energy into heat.

In regenerative braking system, the system that drives the vehicle does the majority of the braking. When the driver steps on the brake pedal these types of brakes put the vehicle's electric motor into reverse mode (generator mode), producing electricity that is then fed into the vehicle's batteries

 

Vehicles using regenerative brakes also have a hydraulics braking system, the vehicle's electronics must decide which braking system is appropriate at which time.

 

Automobiles with Micro Hybrid System

 

Some of the earliest vehicles to use this technology were the Volkswagen Polo "Formel E" and Fiat Regata "ES" models of the 1980s. These early implementations could not get much commercial success due to their pricing.

 

Toyota has been selling cars with start-stop system for several years in Japan. Both Toyota and Mazda will be introducing stop-start technology available also outside of Japan in some of their 2009 model year vehicles, and Renault will introduce the technology in all of its European models by 2010.

 

Fiat introduced the Robert Bosch GmbH made system in the end of 2008 in Fiat 500, while Volvo introduced it in 2009 in its DRIVe models

 

Micro hybrid in India

 

Mahindra & Mahindra introduced the stop start based Micro Hybrid system to Indian Automotive market. This involved home grown technology for vehicles with mechanical fuel injection and later JV with BOSCH for common rail based vehicles. It is known as "Fuel Smart" and is implemented in its SUV's Mahindra Scorpio, Mahindra Bolero.

 

Tata Motors has later introduced this system on their LCV Tata Ace.

 

There are many others vehicles which will implement Start stop in near future.

 

 

 

Important Points to Remember:

 

1. The non-Electric vehicle with Start-stop systems is known as Micro Hybrid

2. In many texts Start-Stop system is referred as Micro hybrid. But in actual Start-Stop is a subsystem of Micro hybrid not the full system.

3. Many people have misconception that there is no difference between Micro Hybrid and Mild Hybrid but that's not true.

4. The driver can deactivate the Start-Stop system at any time, and vehicle will act as normal ICE vehicle.

 

 

Further Reading

 

I will add more details on below topics in my future articles:

- Detailed Working of Start-stop System in non Electric Vehicle (Micro Hybrid)

- Difference in Micro and Mild Hybrid such as Electrical Power difference and the features.

- Component of Micro Hybrid System

- Regenerative Braking

- Hybrid Electric Vehicle and electric drive