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Car battery & Inverter need help

  1. Apr 3, 2010 #1
    Hey all .. i happy to join this forum because of the amount of information that it has ..

    In our city , the electricity cut down for long time may be 10 hours in a day ..
    I want to make a device so i can convert the car battery voltage ( 12V DC) to (220V AC)
    this device called Inverter .. i searched for it on amazon , its price was very suitable , but the problem it i cant get it in our city ..
    So i want to make it myself , so please give me the help and steps to build it , the needed inverter is 500W or 1000W inverter ( at least 500W) ..... and please me a devices which contains the electronic parts that i can use in the inverter .. we have difficult to find the parts in the shop ... so please give me a way to build it by electronic parts which is most common in the shop or the old devices .

    another question is how many hours that (a buttery with 40Amp/h ) can give me hours with 500w device
    Thank you very much
     
  2. jcsd
  3. Apr 3, 2010 #2

    vk6kro

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    For each amp you get at 240 volts, the battery has to supply 20 amps plus whatever losses occur in the inverter.
    So, even at 300 watts out, the inverter will flatten a typical car battery in less than an hour.

    Plus, you have to pay for the power to charge the battery.

    Have you considered getting a small gasoline generator to provide power?

    another question is how many hours that (a battery with 40Amp/h ) can give me hours with 500w device

    500 watts is 41.66 amps at 12 volts. So if the inverter was 100% efficient, the battery would last 57.6 minutes. However, inverters are not 100 % efficient and the amp-hour rating of batteries is only a guide, so it would be more like 30 minutes.
     
    Last edited: Apr 3, 2010
  4. Apr 3, 2010 #3
    no need for gasoline generator to provide power .. the electricity cut for 10 hours and then it get back for the remain time (14 H) ....
    and i can understand from your reply that the battery with 40amp can give me just 1 hour ???? for a device work on 500w ........

    thanx vk6kro
     
  5. Apr 3, 2010 #4

    mgb_phys

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    Yes, a 40AmpHr battery contains 12*40WHr of energy
    And a car battery can only be discharged to about half the rated capacity without damaging it.
    For a backup power you need deep discharge (also called marine) batteries - they are, of course, more than twice as expensive.
     
  6. Apr 14, 2010 #5

    mheslep

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    That depends greatly on how fast you try to use the energy, condition of the battery, and its temperature.
     
  7. Apr 14, 2010 #6

    mgb_phys

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    Yes - and I pointed out that you can only get about half this out of a regular car battery.
    But the OP was confused about the whole Amps/Amp-hours/ Energy/capacity thing
     
  8. Apr 14, 2010 #7

    mheslep

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    Last edited by a moderator: Apr 25, 2017
  9. Apr 14, 2010 #8

    mheslep

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    Ok, though it is also true (energy is not a constant V*amp-hours) of the deep discharge marine batteries.
     
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