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Boost Converter To Charge Laptop From Car Battery Problem

Discussion in 'Power Electronics' started by Moh001, May 24, 2017.

  1. Moh001

    Moh001

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    May 4, 2017
    I am using 3A boost converter to charge laptop from 12v acid battery, the laptop draws 3amp and the boost converter starts to burn out, what should i add to it to limit the current and protect my laptop?? Resistor capacitor diode???
     
  2. davenn

    davenn Moderator

    13,139
    1,704
    Sep 5, 2009
    you are looking at it the wrong way

    you said the laptop needs 3A ... then get a boost converter that can supply at least 3A preferably more 4+ Amps so that the converter
    isn't running at its limit
     
  3. Moh001

    Moh001

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    0
    May 4, 2017
    actually the laptop needs at max 1 amp usually it needs 0.5 amp as i measure its original charger, i want to limit the carrent to 0.5 amp, the problem whenever i add any resistor to the out of the boost converter the current stops!!
     
  4. davenn

    davenn Moderator

    13,139
    1,704
    Sep 5, 2009
    you very sure about that ??

    I haven't seen a laptop produced over the last 10 yrs that doesnt need at least 3A and many up to 5A

    what is the make and model of laptop

    photo the label on the back of it showing power requirements
    also photo the label on the power pack
     
  5. Moh001

    Moh001

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    May 4, 2017
    here is the laptop back and its adapter, the thing is, when i plug it to the laptop and put Ameter in between it reads about 0.5 Amper charging ratio, and when i overuse the laptop it gets up to 1 amp, sidenote ( when i did this measurement, the battery was nearly fully charged)

    upload_2017-5-26_6-14-3.png

    upload_2017-5-26_6-15-24.png
     
    Last edited by a moderator: May 25, 2017
  6. Audioguru

    Audioguru

    2,447
    542
    Sep 24, 2016
    The label shows a 19.5VDC/2.31A adapter. It says 45W (19.5V X 2.31A) so the power and current must be when the battery is dead. Your ammeter has some resistance that reduces the current reading.

    Either the boost converter cannot produce its rated 3A output without burning or its output voltage is too high causing the current to be too high.
     
  7. Moh001

    Moh001

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    May 4, 2017


    so what to do? buy 6A boost converter?
     
  8. Tha fios agaibh

    Tha fios agaibh

    1,852
    585
    Aug 11, 2014
    A fuse will limit the current and protect your laptop.
    You need to check both the input voltage from the battery and the output voltage from the booster. It should put out 19.5v while the battery side should be at least 12.5v
     
  9. Audioguru

    Audioguru

    2,447
    542
    Sep 24, 2016
    I think the cheap (ebay?) "3A" boost converter is actually 0.3A but the dot is so small it cannot be seen.
    Please post a video of it smoking and burning.
     
  10. BobK

    BobK

    7,542
    1,612
    Jan 5, 2010
    Those cheap boards often require a heat sink added to reach their rated output. Sometimes they even say so.

    Bob
     
  11. Moh001

    Moh001

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    0
    May 4, 2017
    thank you all :)
     
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