Hybrid Electric Vehicles: Batteries doc

Hybrid Electric Vehicles: Batteries UKo ¨ hler, Johnson Controls, Hannover, Germany & 2009 Elsevier B.V. All rights reserved. Introduction The idea of combining electrical engines and internal combustion (IC) engines has a long history. In 1901 J. Lohner and F. Porsche had already presented a first hybrid electric vehicle (HEV). But this revolutionary concept did not reach full maturity because the electrical components were not developed. The main concer n was the battery, a high-performing battery system with ac- ceptable long-term endurance was not available at the time. The battery of the vehicle shown in Figure 1 had a weight of not less than 1800 kg. It was not until the end of the twentieth century that HEVs became a serious alter native to vehicles propelled by an internal combustion engine. The Toyota Prius appeared on the market in 1997 and was the first HEV series vehic le in history. A second version with improved performance came out in the year 2003 (Figure 2). Mainly its fuel-saving and extremely environmentally friendly technology were the drivers for the considerable market success since that time. Triggered by the tech- nical opportunities for drastically reducing fuel con- sumption, other car manufacturers such as Honda and Ford developed their own products. Almost all car pro- ducers in the world are now working on HEVs with the clear goal of meeting the demand for fuel-saving and environmentally compatible vehicles. There are several different vehicle concepts covered under the term hybrid vehicle. The following description is to explain the differences in the technologies that have consequences for the battery system used for them. Full Hybrid Electric Vehicles The most popular representative of a full hybrid electric vehicle (FHEV) (also called strong HEV) is the Toyota Prius (Figu re 2). This type of vehicle uses the electrical storage system alone for relatively short periods in which the combustion engine would run with a lower energy efficiency. Regenerative braking, in which reclaimed en- ergy is stored in batteries, is an important feature. Pure electric driving is possible for short distances, but playing only a minor role. It is regarded as an interesting feature for some special situations such as silent cruising in re- mote areas. For energy efficiency reasons, the electrical drive system operates at voltage levels a bove 200 V. The efficient combination of both, the combustion engine and the electrical drive system, enables a reduction of fuel consumption up to 40% in comparison to normal com- bustion engine-propelled vehicles. Mild Hybrid Electric Vehicles Mild hybrid electric vehicles (MHEVs) are a technical alternative to the FHEVs. In comparison to the FHEV, the MHEV needs a lower degree of electrical power performance . Electrical operation is mainly concerned with vehicle start and acceleration phases. Regenerative charging under deceleration and braking contributes to a reduction of fuel consumption. Pure electrical driving is not provided. The electrical drive system of MHEVs operates typically at voltages between 100 and 200 V. Earlier tendencies to realize MHEVs with 42 V systems Figure 1 Porsche–Lohner hybrid electric vehicle (HEV) 1901. Source: Wikipedia. Figure 2 Toyota Prius hybrid electric vehicle (HEV) 2003. Source: Toyota website. 269 . Hybrid Electric Vehicles: Batteries UKo ¨ hler, Johnson Controls, Hannover, Germany & 2009 Elsevier B.V. All rights reserved. Introduction The idea of combining electrical engines. vehicles. Mild Hybrid Electric Vehicles Mild hybrid electric vehicles (MHEVs) are a technical alternative to the FHEVs. In comparison to the FHEV, the MHEV needs a lower degree of electrical power performance. realize MHEVs with 42 V systems Figure 1 Porsche–Lohner hybrid electric vehicle (HEV) 1901. Source: Wikipedia. Figure 2 Toyota Prius hybrid electric vehicle (HEV) 2003. Source: Toyota website. 269