BATTERY TERMINOLOGY rev 2

BATTERY TERMINOLOGY
Batteries are used for a wide variety of services throughout technology today. To
begin to study battery operation and characteristics, a few terms that are used
with batteries must be understood.
EO 1.1 DEFINE the following terms as they relate to
batteries and voltaic cells:
a. Voltaic cell
b. Battery
c. Electrode
d. Electrolyte
e. Specific gravity
f. Ampere-Hour
Voltaic Cell

The term voltaic cell is defined as a combination of materials used to convert chemical energy
into electrical energy. A voltaic or chemical cell consists of two electrodes made of different
types of metals or metallic compounds placed in an electrolyte solution.
Battery
A battery is a group of two or more connected voltaic cells.
Electrode
An electrode is a metallic compound, or metal, which has an abundance of electrons (negative
electrode) or an abundance of positive charges (positive electrode).
Electrolyte
An electrolyte is a solution which is capable of conducting an electric current. The electrolyte
of a cell may be a liquid or a paste. If the electrolyte is a paste, the cell is referred to as a dry
cell; if the electrolyte is a solution, it is called a wet cell.
Specific Gravity
Specific gravity is defined as the ratio comparing the weight of any liquid to the weight of an
equal volume of water. The specific gravity of pure water is 1.000. Lead-acid batteries use an
electrolyte which contains sulfuric acid. Pure sulfuric acid has a specific gravity of 1.835, since
it weighs 1.835 times as much as pure water per unit volume.
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BATTERY TERMINOLOGY Batteries
Since the electrolyte of a lead-acid battery consists of a mixture of water and sulfuric acid, the
specific gravity of the electrolyte will fall between 1.000 and 1.835. Normally, the electrolyte
for a battery is mixed such that the specific gravity is less than 1.350.
Specific gravity is measured with a
Figure 1 Simple Hydrometer
hydrometer. A simple hydrometer
consists of a glass float inside a glass
tube, as shown in Figure 1. The
hydrometer float is weighted at one end
and sealed at both ends. A scale
calibrated in specific gravity is positioned
lengthwise along the body of the float.
The float is placed inside the glass tube,
and the fluid to be tested is drawn into
the tube. As the fluid is drawn into the
tube, the hydrometer float will sink to a
certain level in the fluid. The extent to
which the hydrometer float protrudes
above the level of the fluid depends on
the specific gravity of the fluid. The
reading on the float scale at the surface
of the fluid is the specific gravity of the
fluid.
Ampere-Hour
An ampere-hour is defined as a current
of one ampere flowing for one hour. If
you multiply the current in amperes by
the time of flow in hours, the result is the
total number of ampere-hours. Amperehours
are normally used to indicate the
amount of energy a storage battery can
deliver.
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Batteries BATTERY TERMINOLOGY
Summary
Battery terms are summarized below.
Battery Terminology Summary
A voltaic cell is a combination of materials used to convert chemical
energy into electrical energy.
A battery is a group of two or more connected voltaic cells.
An electrode is a metallic compound, or metal, which has an abundance
of electrons (negative electrode) or an abundance of positive charges
(positive electrode).
An electrolyte is a solution which is capable of conducting an electric
current.
Specific gravity is defined as the ratio comparing the weight of any liquid
to the weight of an equal volume of water.
An ampere-hour is defined as a current of one ampere flowing for one
hour.
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BATTERY THEORY Batteries
BATTERY THEORY
A battery converts chemical energy to electrical energy. This conversion enables
electrical power to be stored.
EO 1.2 STATE the purpose of a battery.
EO 1.3 DESCRIBE the operation of a simple voltaic cell.
EO 1.4 STATE the chemical equation for the reaction
that occurs when a lead-acid battery is being
charged or discharged.
EO 1.5 EXPLAIN the relationship between specific
gravity and state of charge of a lead-acid battery.
Batteries
The purpose of a battery is to store chemical energy and to convert this chemical energy into
electrical energy when the need arises.
As described in previous chapters, a chemical cell (or voltaic cell) consists of two electrodes of
different types of metals or metallic compounds and an electrolyte solution which is capable of
conducting an electric current.
A good example of a voltaic cell is one that contains zinc and copper electrodes. The zinc
electrode contains an abundance of negatively charged atoms, and the copper electrode contains
an abundance of positively charged atoms. When these electrodes are immersed in an electrolyte,
chemical action begins. The zinc electrode will accumulate a much larger negative charge
because it dissolves into the electrolyte. The atoms, which leave the zinc electrode, are positively
charged and are attracted by the negatively charged ions of the electrolyte; the atoms repel the
positively charged ions of the electrolyte toward the copper electrode (Figure 2).
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