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UPS charger output

Discussion in 'General Electronics Discussion' started by Yonu, Jul 28, 2014.

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  1. Yonu

    Yonu

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    Jul 28, 2014
    Ok all this may have came up before and if it has I am sorry I had no results from a search.

    What I am trying to do is take a standard APC Back-ups 400 and disable the 110v inverter and use it as a 12vdc UPS I know that there are some that exist but they don't have PC monitoring which I need. the problem I am having is that I need atleast 5amps output on the 12v side inorder to keep a charge on the battery and run the devices 3amps minimum for my devices. It is my understanding that the charger in the UPS is only rated for 1.5amps. So I would like to figure out a way to increase the output.

    Thanks,
    Yonu
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    The UPS's battery charger is only used to recharge the battery after an outage, and to keep it topped up. You should not draw current continuously from the battery; the charger is not designed to deal with that.

    Use a separate, line-powered 12V power supply to power your loads while power is available, and only draw current from the battery during an outage.

    You can use diodes to merge the two sources together. As long as the power supply voltage is higher than the maximum battery voltage, the load will draw current from the power supply, not the battery. So use a power supply that produces at least 13.8V (assuming it's a standard lead-acid or SLA/VRLA battery in the UPS). Then use two diodes (or a double diode with commoned cathodes) to "diode OR" the positive sides of the power supply and the backup battery together. If the power supply is designed so it can have voltage fed into its output while it's not running, then you only need one diode, from the battery.
     
  3. Yonu

    Yonu

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    Jul 28, 2014
    Ok I think that makes sense was hoping not to have a separate PSU.but was worth a shot. was actually hoping someone would say there was a point in the ups to pull the 12v from Hey one can hope.

    Thanks,
    Yonu
     
    Last edited: Jul 28, 2014
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