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110v 400w Current limiter

Discussion in 'General Electronics Chat' started by Cameron_Toews, Sep 8, 2017.

  1. Cameron_Toews

    Cameron_Toews New Member

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    I have an inverter inside my pickup truck. It is rated at 110v ac and 400w. I want to be able to charge my batteries for my tools, but the inverters built-in protection cuts it off every time i plug the charger in. The charger only pulls 2.1A but it obviously has an inrush current which sends the inverter into protection. I'm looking to build a small device that would basically act as a current limiter, to minimize the inrush of the charger first trying to crank on. I'm picturing a standard plug that has male and female on it, acting as an inline device to limit current.

    I figure i could use an ntc thermistor but my knowledge of these is very limited, i am an electrician by trade but have done some electronics work over the years but it has been sparse at best.
     
  2. Colin

    Colin Member

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    Get a 1.2 amp-hr battery and put it on the output socket. Wait 1 min and now plug in the charger.
     
  3. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Last edited: Sep 9, 2017
  4. dave

    Dave New Member

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  5. Colin

    Colin Member

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    I was thinking the inverter would not start-up.
     
    Last edited: Sep 9, 2017
  6. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Cameron_Toews and I were thinking of putting the CL in the 120V side of the inverter; not the 12V side...

    Let's say you use a SL15 40004. It has a cold resistance of 40Ω, and a hot resistance of less than 1Ω. We dont know how much the inrush current to his charger is, but we do know that the steady-state current is about 2A. If the charger looked like a short, then the initial current would limited only by the 40Ω, so would be 120V/40Ω = 3A. Once the CL heats up and changes state, at the final charger current the voltage dropped across the CL is 1Ω*2.1A = 2.1V, which he can live with.


     
    Last edited: Sep 9, 2017
  7. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    I have designed power supplies with these "inrush limiters".
    Then the CL is hot it takes 48 seconds to cool off. (data sheet) From my experiance it takes longer. You have a load, unplug, wait 1 minute, plug in. It you don't wait the problem is not solved.
     
  8. Colin

    Colin Member

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    .
     
    Last edited: Sep 9, 2017
  9. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    The worst thing that will happen is that the inverter will shut down as it does now. Waiting for the CL to cool occasionally might be a bit inconvenient, but still better than never being able to charge the batteries...
     

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