Holiday Navigator 2003 Owner's Manual page 326

Electrical Systems - House
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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 figures 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 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. 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 to operate the 120 Volt item. There is also a small efficiency
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. 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% efficiency loss
figure, 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 figure 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
figure 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 filling batteries. To achieve
the highest quality of battery performance and longevity maintain the batteries
in their proper operating range.
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