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User’s Manual—Read before using this equipment
8
PLANNING THE INVERTER SYSTEM
Any large wattage inverter system requires planning before installation. There are several steps
to the planning process so the user must determine the following:
• Maximum inverter wattage required.
• Operating time (run time) needed between battery recharges.
• Battery bank capacity in amp-hours.
• Charger requirement to charge batteries within a practical time.
• Distance between battery bank and inverter.
DETERMINING MAXIMUM APPLIANCE WATTAGE
Maximum AC appliance wattage is the first factor in planning battery and charging systems.
Some Background:
Large microwave oven specifications list cooking power (watts) and appliance power. Appliance
power is the AC load the inverter has to supply.
Most other electrical tools, appliances and audio/video equipment have labels that list the unit’s
power requirements in watts. If the tool or device is rated in amps, multiply the amps by 115
(115V AC) to determine the watts. For example, a power tool rated at 4 amps will draw 460
watts. Determine the wattage of each appliance you need to simultaneously operate. Add all of
the appliance wattages to obtain an estimated “total watts” number. Remember to consider the
startup surge that motorized appliances will cause. Do not exceed the surge rating of this inverter
(3,000 watts) this can cause immediate overload shut down.
At 5,000 watts continuous output, this inverter requires a DC power supply (battery bank)
that can continuously supply the following level of amps for the duration of the run time:
#3742-2 (12V DC Input)
—
300 amps @ 12V
#
3742-4 (24V DC Input)
—
150 amps @ 24V
#3742-8 (48V DC Input)
—
75 amps @ 48V
SIZING THE BATTERY BANK
A battery bank is an interconnection of batteries; in this case, to provide 12 volts. To determine
the minimum battery ampere-hour rating that you will need to operate appliances from the
inverter and any DC appliances powered by the battery bank, follow these steps:
(The following calculations are specific to 12V systems. For 24V or 48V systems, a different
calculation is required but the same principles should apply)
1. List the maximum continuous wattage that an inverter has to supply.
2. Estimate the number of hours each appliance will be in use between battery recharges. This
will vary. For example, a typical home-use coffee maker draws 500 watts during its brew
time of 5 minutes, but maintaining pot temperature only requires 100 watts. Typically, a
microwave oven only operates for a few minutes. Refrigerators and air conditioners cycle
on and off. Some longer operating time appliances are lamps, televisions, computers and
sound systems.
3. Determine the total watt-hours of energy needed by multiplying average power consumption
in watts by hours of run time. For example: 1,500 watts for 10 hours = 15,000 watt hours.
