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  • Inverter: continuous power consumption?

    Hello just another technical question which is not clear to me:
    When the carputer is off, will the inverter always continue to draw power from the battery if not switched off?

    thanks in advance,
    -m
    My Carputer: http://www.mp3car.com/vbulletin/showthread.php?t=48014

  • #2
    oh for god sake dude!

    AND TO ANSWER YOUR QUESTION BEFORE YOU COMPLAIN:

    of course it uses power if you dont turn it off!

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    • #3
      ok ok, so sorry...
      My Carputer: http://www.mp3car.com/vbulletin/showthread.php?t=48014

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      • #4
        Don't mind him. Yes it will draw power. Nothing to worry about if you're just leaving for a few hours, but don't expect your battery to have anything left after leaving it overnight.

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        • #5
          Some inverters have 'cooling fans' that continue to run after the computer has been turned off. Fans consume a significant amount of power (as compared to discrete components).
          Check out my carputers:
          DVD, GPS, MP3, 6.4" LCD Touchscreen, 5" Headrest LCDs, PSone, DSSC, etc.

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          • #6
            Well thank you for the answers.
            So if I understand it is not a continuous output of (let's say) 300W.
            Power consumption goes accordingly with the power drainage.
            So if the carputer stays off the draining will be drastically lower.
            Is this correct?
            My Carputer: http://www.mp3car.com/vbulletin/showthread.php?t=48014

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            • #7
              GRRR

              yeah buddy, the inverter wont draw 300W unless it is under a high load. It can output 300W so expect the input to be over 300W (due to ineficencies) when calculating the wire and fuses required. But then again I would never draw 300W from a 300W rated inverter. Always keep a healthy margin.

              Whn the PC is off it will draw a small amout of current but this will kill your battery in short term and long term (ie car batteries don't like constant draws and will eventually go tits up on you).

              You need to use some sort of isolation (relay etc) or just turn it off. There are planty of ideas on here so have a look round.

              one more thing: always hook up your inverter to the batttery not the ciggy lighter and put a fuse on the +ve lead as close to the battery as possible. Also, do not mount your inverter in your engine bay (we had one guy do this).

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              • #8
                my monster power inverter says to unplug it when not in use for about a week since it imposes a constant power drain even when switched off...i'm assuming for monitoring temps and turning on/off the fan accordingly

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                • #9
                  depending on your 12v outlets in your vehicle it might not draw anything out of them. in my truck when the key is off the convenience outlets are off. to include the cig lighter. but in some cars they always stay hot... best way to take the guess work out of it is to shut your car down and use a multimeter and measure the output of the socket. or connect a solar cell to your battery to keep a constant charge on it.

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                  • #10
                    A lot of inverters on the market still draw a small amount of power even when switched off. This is why you use a relay.

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                    • #11
                      Originally posted by schapman43
                      A lot of inverters on the market still draw a small amount of power even when switched off. This is why you use a relay.

                      How is a good way to know if it draws any power? I know that the fan on my inverter is only on when the inverter is switched on and never otherwise.

                      Sima 300w

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                      • #12
                        Originally posted by dagnasty
                        How is a good way to know if it draws any power? I know that the fan on my inverter is only on when the inverter is switched on and never otherwise.

                        Sima 300w
                        Use a meter in series with the power input and set to measure current. Be carefull as the meter has to be able handle the current drawn by the inverter (if its turned on and under full load) 300(+) watts (input side)= a draw of 300/12 25amp You can proberly shunt most of thre power with a resistor but its been years since I messed with electronics, ask somebody else about that.
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                        • #13
                          The ammeter should be in series on the GROUND side of the inverter, not the positive side. Red lead to inverter, black lead to ground.

                          The inverter should be switched OFF when you do this, as most multimeters can only handle 15 amps before their fuses blow. Besides, you're looking for current draw when OFF, not on.

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                          • #14
                            i've searched, and i couldn't find an answer to this question (instead of making a new thread) i thought i'd ask here...

                            if you properly wire an inverter to the battery and ground it, in addition to using a startup/shutdown controller....would there still be power consumption? (i'm assuming so)

                            so...if the inverter is continuously draining power, i'd assume installing a relay or a switch would alleviate this...yes?

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                            • #15
                              Yea, the whole point of using a relay/switch is cut the battery power going to the inverter when you turn the car off..... All inverters I have seen draw a little power even when off, so cutting the power to it (by a switch/relay) will of course keep it from draining the battery.
                              Nick
                              '99 Ford Escort ZX2 CarPC <-- RIP Feb '07

                              2006 Chevy Equinox LS (Current Project)

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