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 concern was the battery, a high-performing battery system with acceptable 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. | Hybrid Electric Vehicles Batteries U Köhler Johnson Controls Hannover Germany 2009 Elsevier . 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 concern was the battery a high-performing battery system with acceptable 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 alternative to vehicles propelled by an internal combustion engine. The Toyota Prius appeared on the market in 1997 and was the first HEV series vehicle 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 technical opportunities for drastically reducing fuel consumption other car manufacturers such as Honda and Ford developed their own products. Almost all car producers 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 Figure 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
