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Power Inverter Frequently Asked Questions

Q1: What is an inverter?
Q2: What size of inverter should I use?
Q3: Why can the 1500 Watt inverter not run my 1200 Watt microwave?
Q4: What is meant by the terms "continuous wattage" and "peak surge wattage" on the inverters?
Q5: What is the output wave of the inverter?
Q6: Are there any disadvantages of using "Square Modified Sine Wave" inverter?
Q7: How do I hook up the Inverter? What size cable should I sue and is it included?
Q8: What type of battery should I use (automotive or deep cycle)?
Q9: How long will my battery power supply last before it goes dead?
Q10: Can I know more about Inverter and battery bank selection for specific load?
Q11: What are the Safety Precautions and Installation Tips?
 

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Q1: What is an inverter?
A device which changes direct current (DC) into conventional alternating current (AC) power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few. You just connect the inverter to a battery, and plug your AC devices into the inverter ... and you've got portable power ... whenever and wherever you need it. The power inverter draws its power from a 12 Volt battery (preferably deep-cycle), or several batteries wired in parallel. The battery will need to be recharged as the power is drawn out of it by the inverter. The battery can be recharged by running the automobile motor, or a gas generator, solar panels, or wind. A very simple way to use an inverter for emergency power (such as during a rolling blackout), is to use a car battery (with the vehicle running), and an extension cord running into the house, where you can then plug in electrical appliances.
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Q2: What size of inverter should I use?
The size you choose will depend on the watts of the appliance or tool you want to run (find the power consumption by referring to the specification plate on the appliance or tool). We recommend you to buy a larger model than you think you'll need (at least 10% to 20% more than your largest load).

Example: You want to power a computer with 17" monitor and a lamp.

Computer and monitor: 300 Watts
75 Watt lights: 75 Watts
Total Needed: 375 Watts

For this application, you would need a 400 Watt inverter. You should consider a larger unit than your minimum requirements, as there will likely be a time when you wish you would have bought a higher capacity model.

If the wattage of the appliance or tool is not listed explicitly on the specification, you may use the following formula.
Multiply: AMPS X 120 (AC voltage) = WATTS.

Example: On the microwave shows 10 AMPS for continuous use.
The Wattage is 10 AMPS x 120 V = 1200 Watt

For Power Needed for different applications, please see the POWER CHART .
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Q3: Why can the 1500 Watt inverter not run my 1200 Watt microwave?
The power commonly advertised for microwave ovens are the cooking power (the power delivered to the food) not the power actually consumed by microwave oven. The microwave ovens might consume 40% to 100% more than its advertised cooking power. The recommended inverter to run 1200 Watt microwave is 2500 Watt or larger.
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Q4: What is meant by the terms "continuous wattage" and "peak surge wattage" on the inverters?
The "continuous wattage" is the wattage that the inverter can supply 24/7 as long as the DC input power supply is in good condition (usually, the DC power supply is a car battery). The "peak surge wattage" is the maximum wattage that the inverter can supply for very short period of time (a split of a second)

NOTE: Induction motors such as air conditioners, refrigerators, freezers, microwave ovens, and pumps may have a start up surge of 3 to 7 times the continuous rating. Heat generating appliances such as hair dryers and water heaters will have high peak surges as well.

Example: If the microwave oven has peak surge which is 4 times the continuous wattage, the 1200 Watt continuous microwave ovens will have 4 x 1200 Watts = 4800 Watts peak surge. The recommended inverter to run 1200 Watt continuous and 4800 Watt peak surge microwave is 2500/5000 Watt inverter or larger. In general, induction motors require an initial surge of power to start up ("starting load" or "peak load"). Once started, the tool or appliance requires less power to continue to operate ("continuous load").

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Q5: What is the output wave of the inverter?
Most of the inverters that we carry are "Square Modified Sine Wave."
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Q6: Are there any disadvantages of using "Square Modified Sine Wave" inverter?
"Square Modified Sine Wave" inverters will run most tools and appliances without any problem and are the most common type of inverter on the market. Below are the advantages of "Pure Sine Wave" (also called True Sine Wave) inverters over modified sine wave inverters:
1. Reduces audible and electrical noise in fans, audio amplifiers, TV and some sensitive audio system.
2. Inductive loads like microwave ovens and motors might run faster, quieter and cooler.
3. The following devices that might not work with modified sine wave inverters:
    - Some battery chargers for cordless tools
    - Some new furnaces and pellet stoves with microprocessor control
    - Sensitive electrical or electronic items such as certain medical equipment
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Q7: How do I hook up the Inverter? What size cable should I sue and is it included?

The small inverters (400 watts and under) come with a cigarette lighter adapter, and may be plugged into your car's lighter socket. The small units also come with cables that can be clamped directly to a battery. If you want an inverter that will plug into your cigarette lighter, you must choose one that is 400 watts or less. Larger inverters (500 watts and over) must be hard-wired directly to a battery. The cable size depends on the distance between battery and inverter, and will be specified in the Owner's Manual.

When connecting the inverter to the battery use the thickest wire available, in the shortest length practical.
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Q8: What type of battery should I use (automotive or deep cycle)?

Small Inverters: Most automobile and marine batteries will provide an ample power supply for 30 to 60 minutes even when the engine is off. Actual time may vary depending on the age and condition of the battery, and the power demand being placed on it by the equipment being operated by the inverter. If you use the inverter while the engine is off, you should start the engine every hour and let it run for 10 minutes to recharge the battery.

500 Watt and larger Inverters: We recommend you use deep cycle (marine) batteries which will give you several hundred complete charge/discharge cycles. If you use the normal vehicle starting batteries they will wear out after about a dozen charge/discharge cycles. If you do not have a deep cycle battery, we recommend that you run the engine of your vehicle when operating the inverter.

When operating the inverter with a deep cycle battery, start the engine every 30 to 60 minutes and let it run for 10 minutes to recharge the battery.

When the inverter will be operating appliances with high continuous load ratings for extended periods, it is not advisable to power the inverter with the same battery used to power your car or truck. If the car or truck battery is utilized for an extended period, it is possible that the battery voltage may be drained to the point where the battery has insufficient reserve power to start the vehicle. In these cases, it's a good idea to have an extra deep cycle battery for the inverter (installed close to the inverter), cabled to the starting battery. It is recommended to install an isolator between the batteries.
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Q9: How long will my battery power supply last before it goes dead?

That depends on a lot of variables such as the state of your battery and the amount of power you use. The heavier the demand, the quicker it will drain your battery. Experimenting with your setup is the best way to determine what you will need to do.

If your battery goes dead too soon for your desired application, you can take one of the following actions to extend your operating time:

  • Start you car engine for about 10 minutes to recharge the battery or just keep it running while you are using the inverter. Use your volt meter to keep an eye on the battery level.
  • Attach several batteries together in parallel.
  • Attach a solar charger to your battery source.
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  • Q10: Can I know more about Inverter and battery bank selection for specific load?

    This worksheet will help you determine the inverter and battery bank required to operate your specific loads:

     Load (Sample) Qty Wattage
    (w)
    Conversion to DC Amps
    (C)
    Actual DC Amps
    (A)
    Appliance Run Time
    (hours – h)
    Amp Hours Consumed Between Charge Cycles
          w / 12 C X 1.1   A X h
    19’ TV 1 100 8.3 9.1 4.0 36.4
    Coffee Maker 1 1,000 83.3 91.7 0.5 45.9
    Microwave 1 1,200 100.0 110 0.17 18.7
    Hair Dryer 1 1,600 133.3 146.7 0.17 24.9
     TOTAL   3,900     Total Ah 125.9

    Choosing the right inverter

    When sizing your inverter, calculate the total wattage required at any one time and choose the inverter with a slightly higher power output. (Start up surge should be considered for compressive loads.)

    Determining your battery bank requirements

    1. Converting AC amps to Watts: AC amps x 120 Volts = Watts
    2. Convert Watts to Actual DC amps: (Watts / 12) x 1.1 = actual DC amps
    3. amp hours consumed between charge cycles:
    run-time of appliance (hours) X actual DC amps = amp hours consumed
    4. Number of batteries required:
    (Total amp hours consumed X 2*) / amp hour rating of battery = Number of batteries required
    *Since deep cycle batteries should only be discharged to 50% total capacity, the total amp hours consumed between charge cycles should be multiplied by 2.

    Example:
    amp hours consumed between charge cycle = 126
    amp hour rating of battery = 90 (Group 27)
    (126X2) / 90 = 2.8
    (Round up to the nearest whole number.)
    Therefore, the minimum number of batteries required is three with the above values.

    Typical Battery Amp Hour Rating
    Battery Size Amp Hour Rating
    Group 27 90
    Group 31 105
    4D 160
    8D 220
    6V Golf Cart 225

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    Q11: What are the Safety Precautions and Installation Tips?

    1. Place the inverter on a reasonably flat surface, either horizontally or vertically.
    2. The inverter should not be installed in the engine compartment, due to possible water/oil/acid contamination, and excessive heat under the hood, as well as potential danger from gasoline fumes and the spark that an inverter can occasionally produce. It's best to run battery cables to a dry, cool inverter mounting location.
    3. Keep the inverter dry. Do not expose it to rain or moisture. DO NOT operate the inverter if you, the inverter, the device being operated, or any other surfaces that may come in contact with any power source are wet. Water and many other liquids can conduct electricity which may lead to serious injury or death.
    4. Avoid placing the inverter on or near heating vents, radiators or other sources of heat. Do not place the inverter in direct sunlight. Ideal air temperature is between 50° and 80° F.
    5. In order to properly disperse heat generated while the inverter is in operation, keep it well ventilated. While in use, maintain several inches of clearance around the top and sides of the inverter.
    6. Do not use the inverter near flammable materials. Do not place the inverter in areas such as battery compartments where fumes or gases may accumulate.

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