ELECTRICAL SYSTEMS-HOUSE - 8
153
CAY M A N 2 0 0 7
The hydrometer is
calibrated at 80° F.
Temperature affects the
hydrometer readings.
The higher the electrolyte
temperature, the higher the
speci c gravity reading.
The lower the temperature,
the lower the speci c
gravity reading. Add or
subtract four points for each
10° variance from the 80°
F chart. Readings between
cells should not vary more
than 50 points.
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.
Placing a load on the Battery:
Another test that can be performed is to
place a speci c 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 batteries while
monitoring voltage to see if they will perform to
their speci c rated capacities.
NOTE:
See the chart for temperature
compensation. 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.
Battery Charge Time & Consumption Rate
Calculating Run Times:
Calculating run time gures when operating
120 Volt AC electrical items with an
inverter can be exponential 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 (Ahrs) 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. For example: A
deep cycle battery with a rated capacity of 100
Ahrs. is designed to release current at the rate
of 5 Amps per hour. Multiplying a 5 Amp load
over a 20 hour discharge period equals the rated
100 Ahr. capacity.
Temperature
Correction Chart
030815
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