GLOSSARY
13
Life Number of years of satisfactory float
operation or number of charge-discharge
cycles for motive power operation.
Loss of Charge The capacity loss occur-
ring in a cell or battery standing on open
circuit as a result of local action.
Lug Portion of grid used for support of
the plate group, usually along top edge of
grid, as “hanging lug.” Also, tab on grid
used for connection of plate to strap and
other plates.
Millivolt (MV) One thousandth part
of a volt.
Moss Dendritic crystals of lead (Pb) which
sometimes grow at high-current density
areas of negative plates, e.g. along edges,
at feet, or a plate lugs. May cause a short
circuit within cell.
Moss Shield Plastic or hard rubber per-
forate sheet which insulates the gaps
between negative plates and the positive
strap, and between positive plates and the
negative strap.
Negative Terminal The terminal toward
which current flows (as ordinarily con-
ceived) in the external circuit from the pos-
itive terminal.
OHM A unit of electrical resistance.
Open Circuit The state of a battery when it
is not connected to either a charging source
or to a load circuit.
Open Circuit Voltage The voltage at its
terminals when no appreciable current is
flowing.
Pilot Cell A selected cell of a storage
battery whose temperature, voltage, and
specific gravity are assumed to indicate the
condition of the entire battery.
Plate A pasted grid, either formed or un-
formed.
Polarity An electrical condition determining
the direction in which current tends to flow.
By common usage the discharge current
is said to flow from the positive electrode
through the external circuit.
Positive Plates Consists of the grid and
the active material from which current
flows to the external circuit when the
battery is discharging.
Positive Terminal The terminal from
which current flows (as ordinarily
conceived) through the external circuit
to the negative terminal when the cell
discharges.
Post Terminal or other conductor which
connects the plate group strap to the out-
side of the cell.
Rated Capacity The ampere hours of
discharge that can be removed from a fully
charged secondary cell or battery, at a spe-
cific constant discharge rate at a specified
discharge temperature and at specified cut
off voltage.
Self Discharge Loss of charge due to local
action.
Short Circuit Current The current which
flows when the two terminals of a cell or
battery are inadvertently connected to each
other.
Standing Loss The loss of charge by an
idle cell or battery, resulting from local
action.
State of Charge (SOC) The amount of
electrochemical energy left in a cell or
battery.
Stratification As applied to electrolyte it
is layers of high gravity acid in the lower
portions of a cell, where they are out of
touch with the ordinary circulation of the
electrolyte and thus of no use.
Sulfated A term used to describe any
plate or cell whose active materials
contain an appreciable amount of lead
sulfate.
Sulfation The formation of lead sulfate
on a plate or cell as a result of discharge,
self-discharge, or pickling.
Sulfuric Acid (H
2
S0
4
) The principal acid
compound of sulfur. Sulfuric acid of a high
purity and in dilute form is the electrolyte
of lead-acid storage cells.
Temperature Correction In storage cells,
the specific gravity and charging voltage
vary inversely with temperature, while
the open circuit voltage varies directly
(though slightly) with temperature.
Terminals The terminals of a battery are
the points at which the external circuit is
connected.
Tray Steel enclosure for motive power bat-
tery cells.
Vent An opening provided to permit the es-
cape of gas from a cell or mold.
Vent Assembly A cell venting device con-
sisting of a ceramic vent stone and filler
funnel assembled on a threaded or a quar-
ter turn bayonet base.
Vent Cap See VENT PLUG.
Vent Plug The piece or assembly of
pieces employed to seal the vent and fill-
ing well of a cell cover except for a small
hole in the plug itself which permits the
escape of gas. Vent plugs are usually held
in place either by threads or by a quarter
turn catch (bayonet vent plug), or by a
snap-in fit.
Vent Well The hole or holes in a cell cover
through which gas escapes, fluids are
added or the electrolyte level is checked.
The vent plug or vent assembly fits into the
vent well.
Volt The practical unit of measurement of
electro-motive force or potential difference
required to send a current of one ampere
through a resistance of one ohm.
Voltage The difference of potential which
exists between the terminals of a cell or
battery, or any two points of an electrical
circuit.
Voltage Range The difference between
the maximum and minimum cell voltages
that exist within a battery or string of cells
when all of the cells are charging
or discharging.
Voltmeter An instrument for measuring
voltage.
Watering Adding water to battery
electrolyte to replace electrolysis and evap-
orative losses.
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