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Thread: Low Voltage

  1. #1
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    Low Voltage

    I have a 400 watt modified sine wave inverter I would use with a 12 volt deep cycle battery. I recently purchased a 150 watt inverter to use with my 56 volt leaf blower battery. Both inverters are supposed to produce 120 volts AC. I recently read where a guy had an inverter that only put out 86 volts that fried two fans. So out of curiosity I checked mine. For reference my house outlets produce 124 volts. The smaller inverter put out 77 volts and the larger inverter produced 102 volts. I ran a 24” fan from the larger inverter, and the fan motor did make a louder hum than when run from house outlets. Can someone offer an explanation for the reduced voltages, and will this damage lights, phone chargers, small TV, fan, etc...? Both batteries were fully charged by the way. These inverters would be used during a storm until I could get my generator up and running.

  2. #2
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    How are you measuring the AC voltage on the inverter outputs? If the inverter is generating a modified AC waveform (most cheap inverters do) you will not be able to measure the voltage accurately without a meter that does true RMS. A standard cheaper meter will measure low voltage due to the non-sine AC waveform.

    If the output is really under voltage then yes, it can cause excessive heat and in some cases damage due to increased current, particularly in motors.

    https://www.evaluationengineering.co...nts-with-a-dmm
    https://www.ecmweb.com/design/articl...-motor-voltage

  3. #3
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    Quote Originally Posted by cdb View Post
    How are you measuring the AC voltage on the inverter outputs? If the inverter is generating a modified AC waveform (most cheap inverters do) you will not be able to measure the voltage accurately without a meter that does true RMS. A standard cheaper meter will measure low voltage due to the non-sine AC waveform.

    If the output is really under voltage then yes, it can cause excessive heat and in some cases damage due to increased current, particularly in motors.

    https://www.evaluationengineering.co...nts-with-a-dmm
    https://www.ecmweb.com/design/articl...-motor-voltage
    I’m checking the voltage output with a typical Craftsman handheld meter that measures volts, amps and ohms. Thanks for the links.
    Last edited by Colt Carson; 10-06-20 at 23:19.

  4. #4
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    A few ideas:

    What is the battery voltage while under these loads?

    Inductive loads like 120v fans larger than hand size can be hard on small inverters.

    Test again with other loads (like the 56v charger) if you can.

    You get what you pay for with inverters. No cheap solutions and cheap ones are usually very inefficient with your limited battery power to boot.

    donrowe.com used to be my go-to for decent inverters. They started selling a wider range (including cheap ones) a while back, but may still be a good reference point.

  5. #5
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    I am guessing the modified sine wave power of my inverter causes my basic meter to read the output voltage of the inverter incorrectly. I am going to purchase an AIMS pure sine inverter so I don’t have future issues.

  6. #6
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    Quote Originally Posted by Colt Carson View Post
    I am guessing the modified sine wave power of my inverter causes my basic meter to read the output voltage of the inverter incorrectly. I am going to purchase an AIMS pure sine inverter so I don’t have future issues.
    Maybe so, maybe no.

    What does your meter read on inverter output with no load?

    Do test with non-motor load and report back battery voltage as well.

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