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  1. #1
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    Default Automobile invertors

    Does anybody have an opinion on using those invertors that install under the hood of a car? I've seen them up to 5KW, with 10KW peek.

    On the surface, it seems like a good alternative to a planta or inversor for those that have a car, and may even be cheaper to buy a junker that runs and one of these invertors (the biggest cost under US$600 in the USA) than to buy a traditional planta or inversor setup. Of course, you'd need to have a place where the car can be pulled right up near the house. A car is certainly quieter than your average planta. Is there any argument to the contrary?

  2. #2
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    i have seen many people use those devices in place of a regular inverter. The problem is that you don't have a charger built-in. Therefore many people use a custom built (locally made) charger to charge up the batteries. I would recommend to buy a cheap charger to charge up the batteries instead of using an engine of a car.

  3. #3
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    I thought the alternator in the car charged the battery. If it doesn't produce enough charge to keep the battery charged while using the invertor, then what good is the invertor since it will shortly drain the battery, and I mean real shortly if drawing 5KW. I was imagining using the car with it running, which is much quieter than the plantas I'm familiar with in the under US$2000 price range.

  4. #4
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    if the car is running then you would be using the alternator of the car and running the inverter. But i was concerned with the rising cost of fuel and the old banger that you mentioned would not be very fuel efficient (I would imagine).
    Most dominicans who use this type of inverter use it in conjunction with a locally made (seems like a home made, cheap) charger and connect a couple of 6 volts batteries. They claim that it still comes out cheaper than a real inverter. The problem was that it didn't have an automatic inverter switching; you would manually have to switch it to inverter mode in black outs. Now I see that some techicians are also hooking up a electric relay to make it a complete automatic inverter.
    With all this trouble in mind, why not just get a dominican made inverter from eddy. I bought his latest new design (cheap) and it works as good or better than a trace with far better protections.
    If you are going to run a car in conjunction with a car inverter than you are actually simulating the functions of a gasoline planta (generator).
    Now if you have your car parked outside in the garage and your room is right next to it. Then simply run the DC wires to your inverter and then hook up whatever within the range of its capacity and run whatever you like as long as the car is running. If you shut off the engine, then it will drain the batteries.
    Have fun.

  5. #5
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    Yes, it's a planta without having to buy the planta, and much quieter. Do you know how much a 5KW/10KW peek planta would cost that is as quiet as a car? A lot.

    So if one already has the car, or can get a cheap junker, unless there is some technical reason not to, that seems to be the way to go.

    No batteries to buy, and a car can run a long time on a tank of gas just idling.

    Yes, it's manual switching. Just like most planta setups. The main problem with a Planta is the noise and they don't produce much electricity until you get real expensive, as in the 5KW/10KW peek range).

    Invertors of the normal kind are limited by the batteries. Batteries need to be replaced periodically, and the number you'd need to produce 5/10KW AC is a lot, I'd imagine.

    A 5KW/10KW peek hookup could run a decent sized air conditioner (2KW), a dozen 60 watt lights, a TV and computer, and a refrigerator (1.5KW).

    The car could be left in the driveway and then run a 50' outdoor power cord to the house. Seems pretty good for under US$600 if you have a car. Yes, the gasoline would be more expensive than the planta, so one would only use this for late night operation if one also has a planta.

  6. #6
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    I am not an electrician, EE, but it would be surprised if you could pull 5-10KW out of a car for extend periods of time without overloading the alternator.

    The alternator for the car should be sized for the maximum charging rate of the battery + the average operating electrical usage of the vehical. I can't imagine that this adds up to a constant 5KW output.

  7. #7
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    hold up now jim.
    I hope you are not going to connect a 5 k or even a 3 k load to a car alternator. Its just not gonna happen. I don't have the exact specs of a car alt. output current, but i am sure its not designed to do heavy duty work. Besides, the car inverters are designed (mostly) for light duty work. They are not designed with a cooling fan built-in nor do many little ones have a good sized heatsink or a heavy duty transformer. I would do more research into it before think of connecting an A/C to it.
    Just imagine, if it were such a good setup, don't you think dominicans would have been doing it by now?

  8. #8
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    I agree with both of you, AZB/SJH. That's why I'm asking here. If not, then what could be the purpose of selling 5KW invertors with 10KW peak for cars?

  9. #9
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    5KW inverter doesn't have to be for a car alone. This type of inverter is for huge sized boats or winobago type home vechicles. These vehicles are fitted with heavy duty alternators that can produce enough current to enable you to run heavy duty appliances, TV, PCs etc off your inverter. I would never push an inverter to its limit, Ex: 5KW inverter should anly be pushed to 3 KWs only. If you push the inverter to its limit, thats when things break down.

  10. #10
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    Most alternators cannot output 1KW continuous. Gasoline ---> gets converted to mechanical energy (motor spins fan belt moving) ---> which rotate magnetic circuits in the alternator --> generates electrical energy.

    If this conversion were done with 100% efficiency, then 1 gallon of gasoline would generate 36 KW-H of energy. So 1 gallon of gasonline per day would give you 1.5kW continuous.

    The fact that the alternator cannot give you this continuous power is a minor detail. Alternators were not designed for this. One can be easily built.

    The key question (to which I don't know the answer just yet) is: what percentage of the energy is lost in going fom gasoline to mechanical energy?

    I think this idea has credible merit.

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