Battery Application & Technology
Active material - Constituents of a
cell that participate in the electrochemical
Battery - Two or more cells
electrically connected to form a unit. Under common usage,
the term "battery" also applies to a single cell.
Capacity - Number of ampere-hours
(Ah) a fully charged cell or battery can deliver under
specified conditions of discharge.
Cell - Basic electrochemical unit
used to store electrical energy.
Current - Flow of electrons equal to
one coulomb of charge per second, usually expressed in
Cutoff voltage - Cell or battery
voltage at which the discharge is terminated. The cutoff
voltage is specified by the manufacturer and is a function
of discharge rate and temperature.
Cycle - The discharge and subsequent
charge of a secondary battery such that it is restored to
its fully charged state.
Duty cycle - Operating parameters of
a cell or battery including factors such as charge and
discharge rates, depth of discharge, cycle length, and
length of time in the standby mode.
Electrode - Electrical conductor and
the associated active materials at which an electrochemical
reaction occurs. Also referred to as the positive and
negative plates in a secondary cell.
Electrolysis - Chemical dissociation
of water into hydrogen and oxygen gas caused by passage of
an electrical current.
Electrolyte - Medium which provides
the ion transport function between the positive and negative
electrodes of a cell.
Equalizing charge - Charge applied to
a battery which is greater than the normal float charge and
is used to completely restore the active materials in the
cell, bringing the cell float voltage and the specific
gravity of the individual cells back to equal values.
Float charge - Method of charging in
which a secondary cell is continuously connected to a
constant-voltage supply that maintains the cell in a fully
Gassing - Evolution of gas from one
or more electrodes resulting from electrolysis of water
during charge or from self-discharge. Significant gassing
occurs when the battery is nearing the fully charged state
while recharging or when the battery is on equalizing
Potential difference - Work which
must be done against electrical forces to move a unit charge
from one point to the other, also known as electromotive
Primary cell or battery - Cell or
battery which is not intended to be recharged and is
discarded when the cell or battery has delivered its useful
Secondary battery - A battery that
after discharge may be restored to its charged state by
passage of an electrical current through the cell in the
opposite direction to that of discharge. (Also called
storage or rechargeable.)
Separator - Electrically insulating
layer of material which physically separates electrodes of
opposite polarity. Separators must be permeable to ions in
the electrolyte and may also have the function of storing or
immobilizing the electrolyte.
Specific gravity - Ratio of the
weight of a solution to an equal volume of water at a
specified temperature. Used as an indicator of the state of
charge of a cell or battery.
Sulfation - Formation of lead sulfate
crystals on the plates of a lead-acid battery.
Terminal - External electric
connections of a cell or battery, also referred to as
"terminal post" or "post."
Thermal runaway - A condition that
occurs in a battery (especially valve-regulated types) when
charging energy results in heat generation within the
battery greater than the heat dissipated, causing an
uncontrolled rise in battery temperature. This can cause
failure through cell dry-out, shortened life, and/or melting
of the battery.
Trickle charge - Method of charging
in which a secondary cell is either continuously or
intermittently connected to a constant current supply in
order to maintain the cell in fully or nearly fully charged
Voltage - Electromotive force or
potential difference, expressed in volts (V).