In view of battery costs and environmental considerations, the batteries used to
power these portable devices should preferably be rechargeable. The demand for
rechargeable batteries is increasing in line with that for portable products. Table 1.1
shows the sales of the most important rechargeable battery types in Japan in 1998
[2]. The majority of the rechargeable batteries are manufactured in Japan. Table 1.1
shows that the number of batteries sold increased dramatically in 1998 relative to
1997. More information on rechargeable battery types will be given in chapter 3.
The energy yielded by a portable device in the form of, for example, sound or
motion, ultimately derives from the electrical energy supplied by the mains. The
conversion of energy from the mains to the eventual load inside a portable product
can be described as an energy chain [3], which is shown in Figure 1.2. The links of
the energy chain are a charger, a battery, a DC/DC converter and a load.