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Lead-acid rechargeable battery is
the oldest form of battery in existence; invented
by the French physician Gaston Planté in
1859, lead-acid was the first rechargeable battery
for commercial use.
 Today,
the flooded lead-acid battery remain its domineering
position for automobiles, forklifts and large uninterruptible
power supply (UPS) systems due to its relatively
low cost and ease of upkeep.
During the mid 1970s, maintenance-free lead-acid
battery was develped that could operate in any position.
Known as the SLA (sealed lead-acid) or VRLA (valve
regulated lead-acid), the liquid electorlyte of
these batteries were transformed into moistened
separators in a sealed enclosure. Safety valves
were installed to allow venting of gas during charge
and discharge.
Determine an optimum charge voltage limit is critical;
the result has always been a compromise. A high
voltage limit (above 2.40V/cell) produces good battery
performance but shortens the service life due to
grid corrosion on the positive plate. The corrosion
is permanent. A low voltage (below 2.40V/cell) is
safe if charged at a higher temperature but is subject
to sulfation on the negative plate.
Lead-acid charging is not subject to memory effect;
hence leaving the battery on float charge for a
prolonged time does not cause damage. Lead-acid
does not react to fast charging well; typical charge
time will take somewhere between 8 to 16 hours.
The battery must always be stored in a charged state.
Leaving the battery in a discharged condition causes
sulfation, a condition that makes the battery difficult,
if not impossible, to recharge.
 Lead-acid
battery does not react well under deep cycling.
A full discharge causes extra strain and each cycle
deplete a small amount of capacity of the battery
permanently. To prevent over stressing the battery
through repetitive deep discharge, selecting a battery
with larger capacity is recommended.
Depending on the depth of discharge and operating
temperature, the average sealed lead-acid battery
provides approx. 300 discharge/charge cycles. The
primary factors determining cycle life is gride
corrosion of the positive electrode, depletion of
the active material and expansion of the positive
plates. These changes are most prevalent at higher
operating temperatures. Cycling does not prevent
or reverse the trend.
The optimum operating temperature for the lead-acid
battery is 25°c (77°F). As a guideline,
every 8°c (15°F) rise in temperature will
cut the battery life in half. VRLA, which would
last for 10 years at 25°C (77°F), will only
be good for 5 years if operated at 33°C (95°F).
Theoretically the same battery would endure a little
more than one year at a desert temperature of 42°c
(107°F). |
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Do not place batteries in close
proximity that may cause sparks. |
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SLA batteries are designed for
application in any position, but avoid charging
them in an upside-down position or leakage
of electrolyte from safety vents migh occur. |
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Avoid exposing or locating the
batteries near a heat generating device. |
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Provide enough insulating of
lead wires between the batteires and the application. |
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Do not charge the batteries
in sealed container. |
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Follow the specified charging
method and conditions (such as charging voltage,
current and time). Avoid overcharge or undercharge,
that may shorten battery service life. |
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Charge battery immediately after
deep-discharge, and charge them before use. |
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Never use a cracked, deformed
or leaking battery. |
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Store the batteries under fully
charged state and keep in a dry and low temperature
place. Recharge them at least every six months
during storage. |
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Do not short-circuit or disassemble
the battery. |
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Never dispose the batteries
into fire or garbage bin, especially in countries
where there are legal or voluntary regulations
on recycling of batteries. |
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The battery housing is ABS plastic
material, clean it with soft cloth only. Do
not use organic solvents or adhesives. |
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In the event if eyes contact
with acid (electrolyte), wash eyes with clean,
cold water and consult physician immediately. |
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Electrochemical energy storage is
based on the conversion of chemical energy into
electrical energy and vice versa. for the direct
conversion into electrical energy, the reaction
has to be split up into two separate electrode reactions,
one that releases electrons, and the other one that
absorbs electrons. Then the electron exchange can
be transformed into a current that flows through
the consumer (device).
Below is the overall reaction in charge (right to
left) and discharge (left to right) of lead-acid
battery :
Pb + PbO2 + 2H2SO4
2PbSO4 + 2H2O
This reaction means that during discharging lead
(Pb) and lead dioxide (PbO2) are converted
into lead sulfate (PbSO4) at the negative
and positive electrode respectively. During charging,
both reactions are reversed. In other word, during
discharge sulfate ions (SO42-)
of the sulfurice acid are absorbed into the electrodes.
When the battery is charged, these reactions are
reversed.
Although the design and the construction of the
VRLA battery are different, its chemistry is that
of the traditional lead-acid battery. |
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