the container. In addition, effective utilization of active components in the chemical
reaction is often less than optimal. Electrode reactant materials can become electronically
disconnected, or shielded from the electrolyte, preventing them from participating
in the electrochemical reaction, thereby rendering them passive. They add to
weight and volume, but do not contribute to the transduction between electrical and
chemical energy.
A rule of thumb that was used for a number of conventional aqueous electrolyte
battery systems in the past was that a practical cell could only produce about 1/5–
1/4 of the maximum theoretical specific energy. Optimization of a number of factors
has made it possible now to exceed such values in a number of cases. In addition,
the maximum theoretical values of some of the newer electrochemical systems are
considerably higher than were available earlier.
Some rough values of the practical energy density (Wh/liter) and specific energy
(Wh/kg) of several of the common rechargeable battery systems are listed in
Table 1.1. These particular values are not definitive- they depend upon a number of
operating factors and vary with the designs of different manufacturers; However,
they indicate the wide range of these parameters available commercially from different
technologies.
Another important parameter relating to practical use of batteries is the amount
of power that they can supply, often expressed as specific power, the amount of
power per unit weight. This is highly dependent on the details of design of the cell,
as well as the characteristics of the reactive components. Hence, values vary over a
wide range.
The characteristics of batteries are often graphically illustrated through the use
of Ragone plots, in which the specific power is plotted against the specific energy.
This type of presentation was named after D.V. Ragone, chairman of a governmental
committee that wrote a report on the relative properties of different battery systems
many years ago. Such a plot, showing approximate data on three current battery