Holiday Trip 2012, Owner'S Manual

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2012 Trip
Placing a load on the Battery:
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
batteries while monitoring voltage to see if they
will perform to their specific rated capacities.
Charge Time & Consumption Rate
Calculating Run Times:
Calculating run time figures 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
a short duration, 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. 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 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 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 DC to operate the 120 Volt AC 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
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% 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.