187
2008 IMPERIAL
ELECTRICAL SYSTEMS - HOUSE — 8
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. Multiply a 5 Amp load over
a 20 hour discharge period equals the rated 100
Ahr. capacity.
These discharge
fi
gures are calculated with
the battery starting at 100% state of charge
with the battery at 80º F when the discharge
cycle begins. However, increasing the discharge
load applied to the battery from 5 Amps to
10 Amps on a 100 Ahr battery does not yield
ten 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
fi
ve 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.
When the inverter is used to operate an AC
load it uses approximately ten times the DC
current needed from the battery when inverting
12 Volts DC to operate the 120 Volt AC item.
There is also a small ef
fi
ciency loss of about
10% when inverting.
For example:
When using
the inverter to operate an AC electrical item,
which has a current draw rating of 2 Amps, the
inverter will use over 20 Amps DC power from
the batteries.
Determining Current Consumption:
First determine the amount of current used
by an AC item.
For example:
The television is
rated at 200 watts at 120 Volts AC. Calculate
watts to amps. Divide 200 watts by the
operating voltage of 120, this equals 1.6 Amps.
Multiply 1.6 Amps AC current by a factor of
ten the inverter will use, this equals 16 Amps
DC battery current. Add the revised 10%
ef
fi
ciency loss
fi
gure, this calculates to a total
of 17.6 Amps DC. If the battery bank capacity
is rated at 500 Ahrs., actual elapsed time to
the suggested 50% state of charge would net
viewing time for the television at approximately
13 hours in ideal conditions.
The run time
fi
gure will vary greatly with
the actual state of charge of the battery bank
when the discharge process begins. Ambient
temperature, combined with other working
loads, such as lights and parasitic loads applied
to batteries, affect run times.
Calculating the exact run time is not precise
due to all the variables and equations involved;
however, an approximate time
fi
gure can be
obtained. Proper battery maintenance and charge
cycles affect battery performance. Observe the
battery condition with hydrometer and voltage
readings. Use only distilled water when
fi
lling
batteries. To achieve the highest quality of
battery performance and longevity maintain the
batteries in their proper operating range.
SOLAR PANEL (Optional)
The solar power system consists of one
solar panel with mounts, a Combiner box and
charge controller that can handle up to
fi
ve
100 watt solar panels.
Solar Panel:
The solar panel is a laser-grooved, buried-
grid panel that is capable of delivering about
5 Amps of charge per hour, per panel, in full
sunlight. One 100 watt solar panel delivers
enough power to offset the normal day-to-
day drain on batteries caused by various
parasitic electrical loads, such as transmission
memories, alarm systems, natural self-
discharge of batteries and other like items.
Adding a second, third or more solar panels (up
to
fi
ve, depending upon needs and electrical
consumption) can replace what is drawn out of
the batteries from the operation of lights, water
pumps, inverter, etc., while dry camping.
