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PWM Online Battery Charger

Discussion in 'Power Electronics' started by Xenobius, Aug 26, 2012.

  1. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Here's the same circuit that I posted earlier but with an automotive lamp wired in series with the battery. The addition of a lamp makes it impossible to overtax your power supply. As you can see in the plot I started the simulation with the battery fully discharged at 0 V. The lamp prevents charge currents any higher than shown for two 30W filaments.

    Please read the notes on the schematic regarding the behavior of hot filament lamps. When they are cold their resistance is maybe 1/3 of it's hot resistance. The hot resistance will be its resistance when operated with 12V across it.

    The lamp can be replaced with a high power resistor but at higher expense. One of the benefits of a lamp is that it gives a visual indication of charging current. It will get dimmer and dimmer as the battery charges. When completely charged it will be nearly impossible to see. Well, maybe in the dark. :D
     

    Attached Files:

  2. Xenobius

    Xenobius

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    May 15, 2012
    Hehe oh no don't get me wrong. I only want it as complex enough to make it very reliable and safe :)
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Do you have a schematic of your switch mode regulated supply? If so please post it.
     
  4. Xenobius

    Xenobius

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    May 15, 2012
    Unfortunately no because I bought it however it does have a model number :)
    Its SA-200-12 and here is a link to its datasheet from the shop I bought it from.
    http://www.deeco.com.mt/upload/prod_pdf/SMPS-FLYER-FRONT.pdf

    According to the datasheet, it should output 12VDC however I asked the guy for a 13.8VDC and he said that he would modify it so that it can output 13.8VDC. Originally it has a trimmer to tweak the voltage and this trimmer is still working.

    The guy also told me which resistor he changed (a resistor in series with the trimmer) and so I can modify it myself if I wanted to. So even if the datasheet states 12VDC, mine is modified to get more.

    Cheers
     
  5. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Unfortunately the information in the link isn't useful. I asked for the schematic because I wanted to be sure that if mains power was lost the battery wouldn't back feed into the supply. That's what the Diode earlier in the thread was all about. I think it was ElectroBrains that posted it.
     
  6. Xenobius

    Xenobius

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    May 15, 2012
    You know I think it has more advantages than disadvantages so basically I will do a power diode on the positive to be on the safe side. I mean for just a little heat I think its worth doing.

    Now I need to tackle the reading of the battery level.
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    As long as you can raise your output voltage to compensate for the diode drop that should work fine.
     
  8. poor mystic

    poor mystic

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    Apr 8, 2011
    :)
    I was taught that the correct way of measuring state of charge in a lead-acid cell is by specific gravity measurement. Regular inspections of the cells are not just a good idea; daily measurements of s.g. are standard in the telephone exchanges where I learnt my trade. Keeping a cell at a constant state of charge allows treeing to develop, which destroys the usefulness of the cell, so we cycled our batteries by completely draining them and recharging them regularly.
     
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Been surfing through old post have we?

    Chris
     
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