Running 1500W off car batteries

  1. I'm going to be running an appliance off car batteries.

    Appliance specs:
    120V
    60HZ
    12A
    1500W

    I need to run it for about 6 hours.

    Would a single car battery with an engine running maintain that power?
    Or will i need to connect several up in series??
     
  2. jcsd
  3. Danger

    Danger 9,879
    Gold Member

    I'm no expert, but I suspect that you'd be farther ahead just buying a commercial device and tapping the alternator. Get a good one, though. The cheap units can cause damage to the alternator diodes.
     
  4. Without running the engine, 1500 watts for 6 hours would be like cranking the engine for 6 hr (or 'til the battery goes dead). Running the engine would charge the battery, of course, but I suspect that the alternator would be operating at capacity i.e., get hot. Furhtermore, you'd use a lot of gas running the vehicle engine.

    If you don't do it very often (e.g., 2-3 times per year) it might be OK, but, I bet you'd be money ahead if you bought a small Honda electric plant. At Tru Value I see them for about $1000. They're quiet, light-weight and easy to use.
     
  5. berkeman

    Staff: Mentor

  6. dlgoff

    dlgoff 3,034
    Science Advisor
    Gold Member
    2014 Award

    " Would a single car battery with an engine running maintain that power?"

    You can't run an A.C. appliance with a D.C. battery.
     
  7. ¡Gotcha! ¡Gotme! I just assumed he'd have one of these new high-powered inverters between the battery and his appliances.

    BUT, look at the fine print. He says:"Or will i need to connect several up in series??" Connecting them in series would certainly be a mistake. However, connecting them in parallel may not be too bad. That is until you're ready to go home. Unless you've connected your vehicle battery and the inverter power batteries through isolation diodes (available at Shucks) you won't be able to start your rig when you want to go home.
     
  8. I'm completely lost and thoroughly confused by the above. Power inverters don't have batteries. The take DC in from some source and output AC. Maybe I've misunderstood you. Having batteries in parallel in a vehicle is no big deal. Many vehicles come from the factory this way. Why is series such a big deal? The OP didn't say what kind of appliance is to be run, it's possible it could be run off of DC. In which case 10 batteries in series would be fine.
     
  9. dlgoff

    dlgoff 3,034
    Science Advisor
    Gold Member
    2014 Award

    Look at his specs.
    "Appliance specs:
    120V
    60HZ..."
    He'll need a DC to AC converter.
     
  10. That depends. The spec on the appliance says it is 60 hertz. But until I hear from the OP what it actually is I'm not assuming anything. Plenty of appliances will say that but can just as easily be run on DC. With that kind of wattage rating I'm betting on some kind of heater.
     
  11. NoTime

    NoTime 1,570
    Science Advisor
    Homework Helper

    For the required run time
    10 to 12 12v 80Ah batteries, depending on inverter efficiency, at about $80 each.
    + inverter at $400 to $800.

    Cheaper to buy a generator.

    If the 1500W is just a startup surge I've seen a 1250W generator for about $130 in one of the local auto parts places. Might do the trick depending on just what it is you are trying to run.

    FWIW
    Many appliances will run just fine on DC.
    For example my coffee maker says 10A 120V 60Hz
    It would work on DC.
    Might wreak the switches in short order.
    DC ratings for switches tend to be a lot lower than AC ratings.

    Also some things are not real happy with the squarewave inverters, so you might have to get a sinewave type.
     
  12. Not many appliances run on dc anymore, these days. Even a space heater won't (you'll burn out the little fan in it) Anything with a LCD display won''t because you'll bun out the transformer in the power supply that runs the LCD.
     

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  13. You've never been able to run a space heater that has a fan on it with DC. They are shaded pole motors and require AC. They are wired in series with the element so that if the motor windings open up the heating element will not heat. However, radiant heaters with just a heating element and an on/off switch can easily run on DC. I suspect curling irons and some hair dryers can run on DC. Plain old incandescent lights can run on DC. Engine block heaters can run on DC. Electric hand drills and circular saws can run on DC as long as they don't have variable speed on them. Alot of drills do, but I've never seen a circular saw that does.
    -
    LCD displays have nothing to do with it. There are a host of things that have transformers with no LCD. There are also a host of things that DO have displays that are made to run on DC. It's usually 12 volts, but don't throw things into the discussion that are irrelevant.
    -
    Until the OP comes back and says what is trying to be run, I'm not making any assumptions.
     
  14. You're right. I'm making assumptions again.

    What's an OP?
     
  15. Danger

    Danger 9,879
    Gold Member

    Original Poster.
     
  16. Most average car alternators will charge at about 800watts at full output. This means that eventually your car battery will go dead even with your car running. However, if you are looking for a 1500watt inverter, I see them all the time at automotive parts stores. You may have to parallel a couple battery's as when you draw 1500watts from a single battery, the voltage may drop below a value where the inverter can operate.

    Edit: I just checked my local supplier and a 1500watt inverter is about $100
     
    Last edited: May 5, 2006
  17. Cliff_J

    Cliff_J 789
    Science Advisor

    If his load is inductive, the in-rush current will likely cause the inverter to shut down.

    Also, the length of time per car battery is going to be low, like maybe 15-20 minutes (getting better with more of them with Peukret factor not hurting as much). A car battery might have a lot of storage compared to many batteries, but its still not very much, especially when running a 2HP load.

    As said already, get a generator, much more cost effective and clean solution.
     
  18. NoTime

    NoTime 1,570
    Science Advisor
    Homework Helper

    There is a big difference between 1500w peak power and 1500w continuous.
    You can probably find a 1500w peak power inverter for under $60.
    An inverter that can do 1500w for 6 hours can put out 3000w for a short time.
    If it has to be sinewave then there is anothe big price jump.
     
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