18
Rev.12/31/97
If cells of either lead-antimony or lead-calcium are
undercharged, service will
be poor and battery life short. If
overcharged
, service with either cell type will
be good, but excessive overcharging will shorten life. Proper charging,
means
slight overcharging to cause the
least possible sedimentation and a minimum of
heavy gassing.
This condition requires very little makeup water. No
perceptible sedimentation or buckling of plates occurs during charge at high
or low rates if cells are not allowed to gas vigorously. Sedimentation starts
with gassing and is proportional to the total amount of gas liberated. Lead-
selenium cells do not have the grid growth or the lead-antimony cell
problems. Typical curves of recharge times after 100-percent discharge at
the 8-hour rate are shown in figure 9.
or low rates if cells are not allowed to gas vigorously. Sedimentation starts
with gassing and is proportional to the total amount of gas liberated. Lead-
selenium cells do not have the grid growth or the lead-antimony cell
problems. Typical curves of recharge times after 100-percent discharge at
the 8-hour rate are shown in figure 9.
2.8 HIGH-RATE OVERCHARGING
2.8 HIGH-RATE OVERCHARGING
After a battery is fully charged, continuation of charging current at a high
rate damages positive plates. Violent gassing takes place, bubbles form in
rate damages positive plates. Violent gassing takes place, bubbles form in
the interior of the active material, and the resulting pressure forces bubbles
through the porous active material. The active material restrains the
bubbles sufficiently so that many particles of plate material are broken out.
These particles rise with the bubbles and result in a muddy red or brown
bubbles sufficiently so that many particles of plate material are broken out.
These particles rise with the bubbles and result in a muddy red or brown
color of the electrolyte. Some of this fine sediment settles on negative plates
where it short circuits. The sediment is converted to gray sponge lead and
results in a growth of moss-like sediment deposited on top edges of the
negative plates. This deposit indicates that high-rate overcharging
previously occurred. The battery will overheat on sustained heavy charge
rates. The temperature of the cells should never intentionally be allowed to
exceed 100 °F.
where it short circuits. The sediment is converted to gray sponge lead and
results in a growth of moss-like sediment deposited on top edges of the
negative plates. This deposit indicates that high-rate overcharging
previously occurred. The battery will overheat on sustained heavy charge
rates. The temperature of the cells should never intentionally be allowed to
exceed 100 °F.
2.9 LOW-RATE OVERCHARGING
2.9 LOW-RATE OVERCHARGING
At lower rates of overcharge, bubbling is reduced and sediment falls to the
bottom of the cell. Overcharging at a very slow rate disturbs electrolyte so
little that fine brown sediment falls in a vertical line, forming tiny ridges on
top of the sediment. Ridged sediment is a good indication that the recent
overcharging was not at high rates. Obviously, overcharging should be kept
at a minimum, and ridges should be small.
bottom of the cell. Overcharging at a very slow rate disturbs electrolyte so
little that fine brown sediment falls in a vertical line, forming tiny ridges on
top of the sediment. Ridged sediment is a good indication that the recent
overcharging was not at high rates. Obviously, overcharging should be kept
at a minimum, and ridges should be small.
2.10 UNDERCHARGING
2.10 UNDERCHARGING
If the battery gets too little charging, unconverted sulfate remains on the
plates too long and hardens. The longer plates stay in less-than-full-charge
condition, the harder the sulfate becomes and the more difficult it is to
reconvert. When new, the sulfate is easily converted back to soft active
materials by a normal charge, but a long overcharge is required to remove it
after becoming hard. Sulfate accumulates unnoticed, a little on each
charge, if charging is not enough to eliminate all the sulfate. This residue
build-up continues until a substantial portion of ampere-hour capacity is
lost. The remedy is to increase charging to give a
plates too long and hardens. The longer plates stay in less-than-full-charge
condition, the harder the sulfate becomes and the more difficult it is to
reconvert. When new, the sulfate is easily converted back to soft active
materials by a normal charge, but a long overcharge is required to remove it
after becoming hard. Sulfate accumulates unnoticed, a little on each
charge, if charging is not enough to eliminate all the sulfate. This residue
build-up continues until a substantial portion of ampere-hour capacity is
lost. The remedy is to increase charging to give a
slight overcharge.
This
procedure must be put into practice while the battery is new and followed