Warning, Helpful formulas – Power Drive 2000 User Manual
Page 8
NOTE: The wattage rating applies to resistive loads. The inverter will operate
most AC loads within its power rating. Some induction motors used in
freezers, pumps, and other motor-operated equipment require very high
surge currents to start. The inverter may not be able to start some of these
motors even though their rated current draw is within the inverter’s limits.
Operating time will vary depending upon the type, capacity charge level of the
battery, and the power draw of the AC products you are using. With a normal
vehicle battery and a 100 watt load (such as a small television) you can
expect an operating time of 2 to 3 hours. It is recommended that you start
your vehicle once an hour when using the RPPD2000 for extended periods of
time to prevent draining the battery.
WARNING
: To prevent personal injury or loss of life, never start or leave your
engine running in a poorly ventilated area such as a garage.
Helpful Formulas:
To Convert AMPS to WATTS: AMPS X VOLTS = WATTS
To Convert WATTS to AMPS: WATTS ÷ VOLTS = AMPS
These formulas yield a close approximation of the continuous loads of a
product.
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ma
atte
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p L
Lo
oa
ad
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Multiply: WATTS X 2 = Starting Load
This formula yields a close approximation of the starting load of the
appliance, although some may require an even greater starting load. NOTE:
Induction motors such as air conditioners, refrigerators, freezers and pumps
may have a start up surge of 3 to 7 times the continuous rating. Most often
the start up load of the appliance or power tool determines whether an
inverter has the capability to power it.
For example: You have a freezer with a continuous load of 4 amps, and a start
up load of 12 amps:
4 amps x 120 volts = 480 watts continuous, 12 amps x 120 volts = 1440 watts
starting load
You would need an inverter with peak-surge rating greater than 1440 watts to
run this appliance.
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DC
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Am
mp
ps
s::
AC Watts divided by 12 x 1.1 = DC Amps
This is the size vehicle alternator you would need to keep up with a specific
load; for example, to keep up with a continuous draw of 1000 watts, you
would need a 91 amp alternator.