A battery is an electrochemical device that stores chemical
energy and converts it into electrical energy. It's function is to provide
electrical power independent of power systems or equipment.
Batteries are provided in many shapes and sizes. However,
they are classified into two specific categories:
Primary Battery - one which cannot be recharged
Secondary Battery - one which can be recharged
Primary batteries are discharged once and discarded. Other
than proper storage, there is no special care required to obtain full life
expectancy. On the other hand, secondary batteries are rechargeable and do
need special care in order to provide power for their full life expectancy.
This covers basic information on batteries - conditions
which shorten their life expectancy, preventative maintenance to insure full
life, and the replacement of defective batteries with current replacement
There are four major types of batteries generally used in
emergency lighting: gel lead, pure lead, lead acid, and nickel cadmium. In
general, all batteries consist of a container, some form of electrolyte and
two electrodes (metal plates). The difference between the various types is
the composition of the electrolyte and the type metal used in making the
These batteries are a form of lead acid batteries, except that the
electrolyte is in a gelatin form. Some are designated as lead-calcium and
some as lead-dioxide depending on the material used in constructing the
These come as cylindrical cells of two volts each. The cells contain
spirally wound plates of pure lead, hence the name. Looking like big
flashlight batteries, they are easily recognized and come in various sizes.
These are "wet cell" batteries with a diluted sulfuric acid liquid and lead
plates of several possible variations. They can carry identifications such
as: Lead Antimony, Lead Calcium, Maintenance Free, Long Life Lead and Medium
Life Lead. These designations refer to construction variations and material
used in forming the plates.
These batteries are of the highest quality. They are alkaline nickel cadmium
cells with a potassium hydroxide electrolyte. They can easily be recognized
since the individual cell rate is 1.2 volts.
BATTERIES - TECHNICAL INFORMATION
A battery is rated under ideal conditions, however, in
actual use, these conditions are not always met. Changing temperatures, over
charging, under charging, deep discharge and physical abuse will affect the
performance of a battery. Let's look at what effect, if any, these
conditions have on batteries.
Ideally, batteries should operate with the temperature range to 60 - 80
degrees F to obtain optimum performance and help extend battery life.
Although capacity improves significantly as temperature increases, battery
life also deteriorates as temperatures rise above 80 degrees F rapidly.
Temperatures lower than the optimum operating range can be used to prolong
battery life (storage and shelf life), however, it will reduce available
capacity and battery operating time.
Causes continued high current flow after a full charge is attained. The
water of the electrolyte is decomposed and the battery will age prematurely.
Excessive water loss indicates overcharge.
Causes the current flow to essentially stop before the battery is fully
charged. This allow some of the lead sulfate to remain on the battery plates
which can eventually reduce the available capacity of the battery by causing
sulfation and plate damage.
Can cause the battery to be damaged and impair performance if discharge is
continued after the terminal voltage falls below 80% of nominal. Deep
discharging a battery past its designed end volts can cause the active paste
to loosen from the surface of the plate grid so that the plate will no
longer be able to receive a subsequent charge.
Can shorten life expectancy and/or impair the performance of a battery. Some
A. Storing batteries in excessively warm locations can cause
accelerated self discharge and affect active plate materials.
B. Storing batteries directly on concrete or dirt floors
will also accelerate self discharge.
C. Dropping a battery can cause internal and/or container
D. Avoid commercial battery "rejuvenator" solutions which
can cause batteries to degrade.
E. Tap water contains impurities, so use only approved
distilled or de-ionized water to maintain electrolyte levels.
F. Loose connections, as well as making or breaking
connection while batteries are in use can cause heat up and damage to the
connectors and/or terminal posts.
G. Shorting a battery can also cause damage to the terminal
post as well as internal damage to the battery.
H. Battery failure can also occur from shallow
charge/discharge cycles and the battery appears to have lost capacity. This
is sometimes referred to as "memory" effect. It is rarely seen, and only
occurs with sintered style Nicad batteries.
Aside from failures due to normal age deterioation, more
conditions leading to battery failure can be prevented or minimized through
proper storage, installation and maintenance. Before storing a battery, a
pre-storage check for possible damage or electrolyte leakage should be
performed. Batteries should always be fully charged and stored in a clean,
cool (60-70 degrees F), dry area away from potential sources of heat or
external ignition, such as heating units, direct sunlight or adjacent
electrical equipment. When battery leads and/or intercells are needed, they
should be of the correct thickness needed for the applied load current. Care
should also be taken that the correct "battery connection diagram" is used
to install the batteries before making connections. When connecting, care
should be taken that all contact surfaces, particularly the connecting
posts, are clean. All connections should be tight and resistance free.