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Rev.12/31/97
contain little antimony and do not have antimony migration like lead-
antimony cells.
antimony cells.
Fully charged lead-antimony cells discharge internally by an action between
active material and the grid. Impurities may hasten this action and may
result in visible or invisible changes on the plates depending on the types of
impurities present.
active material and the grid. Impurities may hasten this action and may
result in visible or invisible changes on the plates depending on the types of
impurities present.
No metals should be put into the electrolyte at any time, except a
cadmium test electrode.
Impurities may prevent a proper floating voltage from
keeping up the charge and may prevent an equalizing charge from
equalizing voltage, so a higher floating voltage may be required.
equalizing voltage, so a higher floating voltage may be required.
The rate of self-discharge is decreased by using a lower specific gravity. The
rate increases as the cell temperature rises, as may be seen on the curves of
figures 5 and 6. The charge will not be lost if a small charging current, just
equal to the self-discharge rate, is given to the cell. This charge is known as
a trickle charge and is usually made a little larger than necessary so as to
rate increases as the cell temperature rises, as may be seen on the curves of
figures 5 and 6. The charge will not be lost if a small charging current, just
equal to the self-discharge rate, is given to the cell. This charge is known as
a trickle charge and is usually made a little larger than necessary so as to
gradually restore losses caused by small loads connected to the battery.
Self-discharge increases with age to perhaps five times the initial rate. This
process is believed to be caused by the antimony being deposited on the
process is believed to be caused by the antimony being deposited on the
negative plate in a form that behaves as an impurity. Many batteries use
calcium instead of antimony as the alloying material, which reduces the
internal discharge as indicated on figure 7.
calcium instead of antimony as the alloying material, which reduces the
internal discharge as indicated on figure 7.
2.6 TEMPERATURE CHARACTERISTICS
2.6 TEMPERATURE CHARACTERISTICS
Operating temperature greatly affects performance of storage cells. Capacity
is greatly reduced when cold, as shown by figure 8. The self-discharge rate
is increased at warm temperatures, as shown by figure 7. The temperature
at which the electrolyte will freeze and burst cells is lowered as specific
gravity rises. Little danger of freezing exists if the battery is kept well
charged.
is greatly reduced when cold, as shown by figure 8. The self-discharge rate
is increased at warm temperatures, as shown by figure 7. The temperature
at which the electrolyte will freeze and burst cells is lowered as specific
gravity rises. Little danger of freezing exists if the battery is kept well
charged.
If charging current is kept constant, charging voltage will rise to a final value
and is one indication that full charge has been reached. This final voltage
increases greatly as the cell gets colder, as shown by figure 5. For this reason,
and is one indication that full charge has been reached. This final voltage
increases greatly as the cell gets colder, as shown by figure 5. For this reason,
do not try to terminate an equalizing charge by a relay that operates at a
constant voltage. This procedure would only work correctly for one
temperature. Relays are available where operating voltage varies with
temperature. This charge control must be subject to the same ambient
temperature as the battery.
constant voltage. This procedure would only work correctly for one
temperature. Relays are available where operating voltage varies with
temperature. This charge control must be subject to the same ambient
temperature as the battery.
If charging voltage is held constant, final charging current increases with
temperature, as also shown in figure 5. This condition is needed to offset
the increasing internal self-discharge current. The constant voltage charge
method automatically keeps the current at the value the battery needs for
replacing both the self discharge and load discharges.
temperature, as also shown in figure 5. This condition is needed to offset
the increasing internal self-discharge current. The constant voltage charge
method automatically keeps the current at the value the battery needs for
replacing both the self discharge and load discharges.
2.7 PROPER AMOUNT OF CHARGE
2.7 PROPER AMOUNT OF CHARGE