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Thread: HELP!!! Need advice - power problems...

  1. #1
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    Post HELP!!! Need advice - power problems...

    I have a 300 watt inverter that is plugged into my cigarette lighter... if the inverter isn't getting enough power, then it will beep and turn on and off, on and off, on and off....

    I already fried one motherboard and I have made a new computer that is ready to go into the car, but I don't want to kill this one - so what is the resolution to this power problem?

    My guesses are that I could get a stronger battery, or wire the inverter directly to the battery...

    Any comments or advice is greatly appreciated

    Thanks all -

  2. #2
    Maximum Bitrate gizmomkr's Avatar
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    When is it turning off and on ?

    does it just sit there aqnd do it constantly, or is it just while the car is cranking or what ?
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  3. #3
    FLAC DodgeCummins's Avatar
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    300 watts at 120v = 3 amps (approx)

    So your Inverter is probably pulling about 5 amps. Your cigarette lighter is probably fused for 10 amps. No problems yet.

    However it is that connection between the inverter plug and the cigarette lighter plug. You probably aren't getting a good contact.

    You could string wire to the battery and put a fuse at the battery end.

    Or you could splice into the wires running to your lighter socket (not a crimp on splice, actually strip some wire and add some solder) and solder your inverter input direct to that circuit. It will still be fused in the fusebox.

    Problem is, once you clip the cords, if it is still cycling then you will have to do some fiddleing around to return it.

    BTW the center contact point in the lighter socket is positive, the shell around the outside is negative...for US anyway.

    Hope that helps.

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    Exclamation

    Yes - actually the inverter is only resetting when the car is idleing - if i get going on the interstate, it will work fine but as soon as I come to a stoplight, the inverter will not be getting enough power anymore and start to beep and reset....

  5. #5
    Maximum Bitrate Meatballman's Avatar
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    Sounds like your battery might be going...and the thing is running off the alternator. You may need a new battery.

  6. #6
    Oms
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    DodgeCummins: just to clarify here, you've got the amps way wrong. If the computer is pulling 300W @120V, that's ~2.5 amps, but only on the AC side of the circuit. On the DC side, the inverter is pulling a lot more. Those 300W of power have to come from somewhere; at 12V, 300W is 25 amps, and that's not counting the inverter's overhead.

    Of course, 300W is just the peak power, the computer will not use that much, not continously. But in any case, it's a lot of power to pull through a lighter socket, so you're absolutely right to advise him to wire the inverter straight through.

    mwinkler: could be your alternator going bad, too, or even just the alternator belt. I had the same effect in wet weather with a loose V-belt - the belt would slip a bit, and the alternator just wouldn't put out enough juice.


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  7. #7
    Retired Admin Aaron Cake's Avatar
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    Cool

    It sounds like your alternator has issues. Classic sign of a dying alternator is low voltage at idle, dimming lights, etc.

    To cure inverter problems forever, use a DC-DC converter.

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  8. #8
    FLAC DodgeCummins's Avatar
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    Oms law,

    UR correct sir...I was figuring out the wrong side (I have been working on projects to step down voltage)

    And on that note, my Lighter socket is fused for 10 amps...I am curious what this one is set for.

  9. #9
    Maximum Bitrate gizmomkr's Avatar
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    mwinlker -

    Take your car to a service center, ask them to check the electrical / charging system.
    They have equipment designed especially for that.... (its really just a dumbed down volt meter.... ) but they can tell you if your batery / alternator / charging system is ok.

    Based on your description - something wrong, not with the inverter , with your car.

    Now would be a great time to mention -
    ***To everyone with lots of stuff connected to there car ****

    Your alternator has limits, if you exceed those limits by hooking to much stuff up to it- It will fail ! , your car is not an endless source of power.....

    Dodge - you seemed to be a bit lost as to how the 10 amp lighter socket runs a 300 wat inverter : The inverter is capable (s/p) of supplying UP TO 300 watts, it is not alwayse drawing that much juice. The same applys to your CPU power supply. a 250 Watt ATX aupply with 1 hard disk pluged into it isnt going to pull 250 Watts. The amount of power drain placed on the system is proportional to the load its driving.

    When you fire up that pc, and the inverter I am willing to bet you draw an average of about 7 amps (depending) +-2 Thats a guess.

    My system draws about 6.5Amps surge (on boot) and then drops to about 4.5Amps

    If you really want to know how much power your system draws- HOOK UP A DMM. (Digital Multi Meter) well I guess you could use an analog meter.... Anny worthwile DMM will have a seting for AMPERAGE. the thing is , you must hook the meter in series with the circuit your trying to test. This means you *MUST* stay within a certin range (determined by the meter) I think radioshack makes one for about 50.00 that goes up to 20Amps. Be carefull, your not soposed to run the equipment off the thing, you just test it, and then unhook it.
    Gizmo-
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  10. #10
    FLAC DodgeCummins's Avatar
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    gizmomkr,

    I agree with everything you say.

    I do not believe the ligher plug is the most efficient power connector. He could have enough resistance in the lighter plug to lower the input to the inverter a bit, that coupled with the fact that a stock alternator produces almost no power at idle, could be enough to flake the machine out.

    BTW they make aftermarket alternators that put out around 60 amps at idle and 120 or so at peak rpm.

    Gunk on your battery posts, under the battery connectors will also lower the output, scrape it with a knife to get down to the shiny metal (a battery post brush will shine up the corrosion, not always clean it off)

    Batterys have potential and current. The potential is the 12v by design, with the multiple layers adding up to 12v. Current is the rate it can put out that 12v. A bad battery can measure 12v with no load on it, but as soon as you turn some stuff on, the output drops rapidly. Most auto repair shops can do a load test on the battery.

    A battery that came from the factory with the car will die in 3 years or less.
    Replace it with the most CCA (cold cranking amps) you can fit in the box.

    My trucks batteries (it uses 2) died almost exactly 3 years after manufacture. Right before I changed them, I could only crank the engine for 4 seconds before the power dropped to far to kick in the starter relay.

    But the stereo equipment worked just fine. (of course this is an extreme case)

    Good Luck.

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