Hybrid Electric Vehicles: Batteries doc
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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.
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