does anyone know of a more efficient 3k/6k 12v inverter.

MEK1954
MEK1954 Registered Users Posts: 23 ✭✭
in General Solar Power Topics #1
My 12v 4K/8k inverter is consuming 20 amps and my demand is only 2.08 amps is this normal seams a little inefficient to me, does anyone know of a more efficient 3k/6k 12v inverter.
Mark



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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    edited December 2020 #2
    MEK1954 said:
    My 12v 4K/8k inverter is consuming 20 amps and my demand is only 2.08 amps is this normal seams a little inefficient to me, does anyone know of a more efficient 3k/6k 12v inverter.
    Really not sure what we are looking at or what you are describing.

    Do you have the input and output voltage?
    If you are using 20 amps at 12.5 volts or 20a x 12.5V = 250 watts. and are outputting 2.08a x 120v= 249.6 watts, Looks pretty good!

    Amps is moot a measure of power, just current. Power is amps x volts.
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  • MEK1954
    MEK1954 Registered Users Posts: 23 ✭✭
    #3
    The AC current and DC currant !!  I should have done the math, thanks.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    edited December 2020 #4
    A 12v 4kVA inverter is not realistic due to near 400 amp max current consumption. Also cheap inverters often have high no-load idle consumption.  Not sure if your 2.08 amp reference is 120 VAC output current or no load inverter 12vdc idle current.  If it is no-load DC idle current that would not be unexpected for a 4kVA inverter.

    You did not state if it is true sinewave or modified sinewave inverter.  If modified sinewave, a Kill-A-Watt like meter will not likely read correctly.

    Reasonable 12v max VA rating inverter is 1500 VA. Generally, the higher the power the inverter, the greater its overhead power consumption.


    As to your readings,  2.08 amp * 120vac = 250 watts at AC output.  DC meter showing 251 watts input.  Never would be that good.

    250 watts AC power output with 95% inverter efficiency is 263 watts from battery and would be a good efficiency for a smaller inverter but at just 250 watt load on a 4 kVA inverter the idle overhead consumption by inverter will likely prevent achieving 95% overall efficiency.

    I specifically stated inverter as VA not watts.  Inverters and generators are rated for VA not watts output.  Their losses are based on current through their switching devices, transformer, and wiring.  Poor power factor loads will impact maximum capability and inverter efficiency. 

    Motors will have inductive power factor in 0.7 to 0.9 range. 

    TV's and other electronic equipment may have simple rectifier-filter capacitor power supplies with power factor in 0.65 to 0.7 range.  Their AC load current profile is short high current pulses at twice AC line frequency. 

    U.S. power grid residential service cost is based on real power and doesn't charge extra for poor power factor loads so manufacturers don't put in extra cost to improve device power factor.  Europe has more regulations on power factor for devices consuming more then 75 watts.  One of worst offenders in U.S. are inverter-based refrigerators, touting high efficiency, with very poor power factors in 0.6 -0.7 range.  Terrible for powering by a battery based inverter. 

    Manufacturers specifically have different unit design for U.S. versus Europe market as they can save a buck or two on manufacturing cost by not including power factor correction for product targeted to U.S. market.

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  • New_Mexico_Will
    New_Mexico_Will Registered Users Posts: 107 ✭✭
    #5
    I used an AIMS UL listed 12 volt 3,000/6,000 watt inverter for a year and a half with no issues.  That thing was (is) a tank.  It even ran my 12" chop saw and small welder without complaints.  The amperage made me nervous, but it never blew a fuse.  I'm definitely happier in 48 volt world, but those wattages at 12 volts are really fine if you manage it correctly. 
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  • MEK1954
    MEK1954 Registered Users Posts: 23 ✭✭
    #6
    DC 20 amps at 12.5 volts or 20a x 12.5V = 250 watts. and are outputting AC 2.08a x 120v= 249.6 watts,
    I asked this question before thinking it through so my inverter is more efficient then I first thought.
    Thank you all for your help.
    Mark
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #7
    RCinFLA said:





    U.S. power grid residential service cost is based on real power and doesn't charge extra for poor power factor loads so manufacturers don't put in extra cost to improve device power factor.  Europe has more regulations on power factor for devices consuming more then 75 watts.  One of worst offenders in U.S. are inverter-based refrigerators, touting high efficiency, with very poor power factors in 0.6 -0.7 range.  Terrible for powering by a battery based inverter. 

    Manufacturers specifically have different unit design for U.S. versus Europe market as they can save a buck or two on manufacturing cost by not including power factor correction for product targeted to U.S. market.

    Inverter based refrigerators do have a poor power factor, this affects the VA rating consumption for the power generation source, the DC-AC inverter in the case of offgrid, however the offset is not subject to the batteries which still supply real power as opposed to apparent power.

    Being that inverter based refrigerators are generally a small load, typically less than 100W,  the effect is minimal since in offgrid as the battery capacity is the primary concern, hopefully the refrigerator is a small percentage of the inverters VA rating, it's high power, poor power factor loads that are of greater concern in offgrid. 

    Whilst the statement is true for the grid utility supplier who needs to compensate for the aggregate of all poor power factor loads, the benifit of inverter based refrigerators offgrid is an acceptable compromise especially the absence of surge current. 



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