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24 volts DC 40 amp voltage stabilizer

Discussion in 'Home Power and Microgeneration' started by RamRod Sword of Baal, Apr 24, 2008.

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  1. I have a particular set up for powering my computers. We are on mains power
    (Australia 240 volts 50 cycles) but I have a system for running the
    computers, it has 4 x 6 volt T105 batteries (24 volt ) and a 2500 watt
    inverter.

    There are as many as 9 computers can be put on line, but in actual fact
    normally it would only be 2 or possibly 3, depending what is happening in
    the house. I cannot see where we would ever have as many as 5 running at one
    time.

    The system allows for running a TV and fridge in case of a power failure.

    The power for the batteries comes from a simple 40 amp 24 volt charger, it
    is a transformer and rectifier. It is a solidly built unit that I had made
    for the job.

    I also had a 25 amp electronic charger but it has failed and needs repair or
    replacement.

    These large chargers are quite expensive here in Australia, for instance a
    24 volt 25 amp charger can run up above $1000.00.

    The inverter is a sinewave job and cost $2500.00 so any idea of throwing
    away what I have and replacing it is not on.



    Now comes the problem. The battery charger being only a simple battery
    charger need the battery voltage to drop quite a bit before you can get a
    large current out of it. I want to maintain around 27 volts in the batteries
    and have the charger put in what ever the inverter is dragging out, so if
    the inverter is using say 20 amps, I need to put in 20 amps, plus a small
    maintenace charge for the batteries and maintain the 27 volts in the
    batteries, so I am not constantly draining and recharging the batteries thus
    reducing their life.

    I have seen one of these devices in the past, but unfortunately lost the
    link.

    It is an electronic 'box of tricks' rated around 40 amps that you can put is
    a DC voltage and get out a constant dc voltage.

    As I can increase the DC voltage from my current simple battery charger to
    up over 40 volts if I so desire, I am looking at buying something that would
    give me a constant or near constant 27 volts, and rated at 40 amps output to
    maintain the batteries at full charge. Of course the 'box of tricks' needs
    to modulate the current to maintain the 27 volts in the system between 0 and
    40 amps

    I understand it might not be able to hold it at exactly 27 volts, but it
    would want it to be somewhere near that number.

    At the moment I seem to be having the problem of either pulling power out of
    the batteries or over charging them, depending on what setting I use on the
    battery charger.

    Has anyone seen such a thing (DC Voltage stabilizer), and knows where I can
    get one, or has a circuit diagram for something like this?

    I have not been able to find anything using Google.
     

  2. I should have made the point that I want to use the DC power from my current
    simple battery charger to feed into a DC to DC voltage stabilizer.
     
  3. Vaughn Simon

    Vaughn Simon Guest

    Perhaps you don't need a stabilizer at all. The problem is that you are
    trying to use that "dumb" power supply to do two jobs at once. Perhaps you need
    to use that "dumb" power supply for the heavy work while you use a much smaller
    "smart" charger to keep your batteries topped off.

    First of all, let me ask you this: If you didn't have the batteries at all,
    would you still trust that power supply enough to run your computers directly
    from it? If no, then stop reading

    If yes, then you can get along fine with a diode isolator (battery backup
    module) which will allow your power supply to normally power your computers, and
    will resort to the batteries only when the power supply dips below the battery
    voltage. (This model won't work for you, but here is a manual for one.
    http://tinyurl.com/69z2mn
    All you really need is two diodes, build it yourself.) You could maintain the
    charge of the battery with a small, but high quality 24-volt battery charger
    like this: http://batterytender.com/product_info.php?products_id=9
     
  4. What I use is a Regulated DC Power Supply, as a Battery Charger.
    I set the Output Voltage of the Regulator, to what I figure should
    be Float Voltage, for the battery type, Minus .3 Vdc. I have a
    pair of L16HD's, in series, that supply the 12 Vdc Buss that runs my
    Radioroom/Office. Using a Regulated Dc Power Supply with the Output
    Voltage set at 13.3 Vdc, and capable of supplying 40 amps. My Base
    Load is usually in the neighborhood of 7 Amps, and jumps to Max of
    50 amps, when one of the Transmitters is operating. The Battery
    Bank will support the load thru ANY Communication Session, and will then
    be recharged back to float, within a few hours after heavy use, all
    while maintaining a Buss Voltage, above 12.3 Vdc. Since I generate
    ALL my own power, and the genset only runs 10 hours a day, and the
    Regulated Power Supply, is not powered unless the Genset is online,
    this keeps my Radioroom/Office running 24/7/365, and the Battery
    Bank fully charged, and back at Float Voltage, at least twice a day.

    The only difference between your cheap Battery Charger, and my Regulated
    DC Power Supply, is the Voltage Regulation Circuits my unit has, after
    the Rectifier.
     
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