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If one cell in a particular battery bank being tested is at a 50% state of charge while
the others are indicating a full charge, charge only that battery to see if the low cell will
come up. At the same time, do not over charge the healthy cells. If the low cell does not
come up after charging, this battery can damage the rest of the battery bank and should
be replaced. An accurate digital volt meter + - .5% will also give an indicator of the
battery’s state of charge. Another test that can be performed is to place a specific load
on the battery for a predetermined length of time equal to that particular battery’s rating.
This machine is usually an adjustable carbon pile that can vary the load being applied to
the battery(s) while monitoring voltage to see if they will perform to their specific rated
capacities.
NOTE:
See the Temperature Compensation Chart. Liquid levels should be even
between the cells of the battery being tested as it will affect the accuracy of the
test.
WARNING:
Sulfuric acid in the batteries can cause severe injury or death. Sulfuric acid
can cause permanent damage to eyes, burn skin and eat holes in clothing.
Always wear splash-proof safety goggles when working around the battery.
If the battery electrolyte is splashed in the eyes, or on skin, immediately flush
the affected area for 15 minutes with large quantities of clean water. In case of
eye contact, seek immediate medical aid. Never add acid to a battery once the
battery has been placed in service. Doing so may result in hazardous splattering
of electrolyte.
Charge Time & Consumption Rate
Calculating Run Times:
Calculating run time figures when operating 120 Volt AC electrical items with an
inverter can be expediential. This is due to battery characteristics. Flow characteristics
of electrons vary with different battery types and chemical compositions. Deep cycle
batteries are generally designed to slowly release a majority of their charge capacity.
Deep cycle batteries are rated in amp hours (Ahr) with the discharge occurring over an extended period of time
before the battery is charged. Engine starting batteries are designed to quickly release large amounts of current
for short durations without depleting battery reserves. Commercial type batteries bridge the gap of deep cycle and
engine batteries. Commercial batteries release medium amounts of current over a longer period of time, but they
are not designed to cycle their charge capacity.
The working range of a deep cycle battery is between 50 and 100% state of charge (SOC). Deep cycle batteries
should not be cycled below 50% state of charge. Discharging a deep cycle battery below 50% state of charge
shortens the life of the battery. Deep cycle batteries use an amp hour rating which is usually calculated over a 20
hour discharge interval. Example: A deep cycle battery with a rated capacity of 100 Ahr is designed to release
current at the rate of five amps per hour. Multiply a 5 amp load over a 20 hour discharge period equals the
rated 100 Ahr capacity. These discharge figures are calculated with the battery starting at 100% state of charge
with the battery at 80º F when the discharge cycle begins. Increasing the discharge load applied to the battery
from five amps to ten amps on a 100 Ahr battery does not yield 10 hours of discharge time. This is due to the
internal reactions which occur when a battery is discharging. Actual discharge time for a 10 amp load may be
closer to eight hours of discharge time. Increasing the load applied to the battery to 20 amps will not yield five
hours discharge time but may be less than three hours. It might be understood as a point of diminishing return.
Calculating applied loads to an inverter to approximate run time from the battery amp hours available is not an
equal trade up when voltage is inverted and amperage is calculated.
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