DC to AC Inverter

Discussion in 'The Projects Forum' started by Dalaran, Jul 13, 2011.

  1. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    I have my solar panel, charge controller and battery all ready to go for a test run. I was hoping to use a 12VDC to 120VAC inverter that was originally made for a car. I hooked it up to a 12V power supply and was astonished to see it drew ~150mA without a load! I guess they don’t make these things too efficient since they don’t need to.

    Can anyone recommend a design for a more efficient inverter, maybe one that I could build?

    My other option, since I was hoping not to have to disconnect inverter when I’m not using it, is to add a switch on the power going to this inverter.

    Anyone have any other suggestions, ideas or comments?

    Thanks!
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    If the no-load current draw is only 150mA, that's pretty darn good. I sincerely doubt you'll be able to do even close to that with a home-made inverter.

    All inverters are going to have current draw even with no load, as long as they are generating the rated output voltage. They really aren't very efficient with light-to-none loading, as there is fixed "overhead" for things like charging/discharging MOSFET gates, powering IC's, etc. thatjust has to happen in order to generate even zero-current output.
     
  4. iONic

    AAC Fanatic!

    Nov 16, 2007
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    150mA. If the inverter uses a fan consider yourself efficient. It sort of depends on the power rating of the inverter and your power needs.
     
  5. Dalaran

    Thread Starter Active Member

    Dec 3, 2009
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    Thanks for the reply everyone... I really didn't realize this was actually reasonable. Is this the same for a large inverter used for home solar applications? Obviously not the same current but there is some draw even when not in use?

    If this is the case then I guess I will need a switch to manually turn on and off the inverter. .15Ah is quite significant in my little set-up, especially when it is not being used more than 50% of the time.

    I had thought they would be in some low power mode where it would sense attempting to draw current and turn on.

    Again, much appreciated.

    edit: The writing is worn off but I believe it was a 75W inverter. There is a tiny fan inside to the best of my knowledge.
     
  6. iONic

    AAC Fanatic!

    Nov 16, 2007
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    75W, that's about as small as I've seen! But, yes, especially if the fan is always on. Sometimes they do not turn on unless there is a current draw. Perhaps if you discard the fan and attach a 1ft x 1ft heat sink you may only consume 50mA in a standby situation. I'm joking about the size of the heat sink. You wouldn't think you would need a heat sink just to make the 110V available. Check the current rating of the fan if it is available. That would give you a decent indication of what the rest of the device would consume.
     
    Last edited: Jul 14, 2011
  7. Audioguru

    New Member

    Dec 20, 2007
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    I have seen those tiny 75W inverters on sale for almost nothing so I agree that their efficiency is not cared about. 150mA at 12V is only 1.8W.
     
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