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Beefing-up a UPS' capacity

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    Beefing-up a UPS' capacity

    UPS = Uninterruptible Power Supply ... as used for protecting desktop PCs from damage in power-outages.

    The CCTV system we had installed in Sri lanka last year is functioning just fine but recent power cuts have revealed that the UPS that keeps it going when Mains power fails, has itself conked out. It was a pricey item being much heftier and with greater battery capacity than the regular little-‘uns that are used for PCs, so I’ve been cracking on sending emails and texts to the installer invoking the guarantee. The batteries look to be black, unbranded, anonymous Chinese jobs, I’m hoping that they’ll replace them with decent ones. It uses 2x 12v in series = 24v and I’ve even considered buying a couple of small car batteries, connecting them in series and wiring to the existing UPS battery connections with extension cables to provide lots of capacity. They should recharge off the UPS circuitry in the normal way ... I'd think?

    What thoughts on this?

    Mike

    24 in series.jpg click to enlarge

    #2
    As with a split charge in a camper using a charging system for a very close warm battery (vehicle) to also charge a distant cooler battery (leisure) means the distant one is never fully charged. Due mostly to lost volts in the extension leads. Never fully charged batteries have shorter lives (talking lead acid) . Larger cross section, short extensions help. What is really needed is a smart charger that senses the battery condition and adapts the output voltage to suit. I do not know if your system already has that?

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      #3
      I don't see why it shouldn't work but leisure type batteries may be more appropriate.
      Is it the batteries that have failed or the charger/inverter components?
      The ones I used to install were only intended to keep the power up long enough to allow the orderly shut down of computers in the event of blackouts.
      Sesquipedalianism:-The overusage of long words.

      Comment


        #4
        Thanks Derek & Jon, I reckon I can keep the cable beefy and the runs short but I take the point that in this instance where the batteries really might be run completely flat by an extended power cut, then leisure type would certainly be best. The installer is coming to inspect and remove the UPS tomorrow, as you say it is not confirmed that the fault lies with the batteries and it could indeed be the charger, inverter or switching circuitry. I should get a result this time but will likely have a crack at the lash-up I've outlined if there is a further failure.

        I wonder if the original cheapo Chinese sealed batteries are deep-discharge? Somehow I doubt it. Fingers crossed for a happy ending to this saga.

        Cheers

        Comment


          #5
          On one contract job I had, I used to have to install UPSs in each and every comms cabinet we installed. That was for Scottish Power. I asked the customer why they wanted UPSs, and they replied with a smirk - "we know what we are generating, and we don't like it". The 230v nominal wobbles all over the place, and is full of high frequency spikes. The main ide of their installation was to provide a constant smooth voltage to the comms equipment. The incoming mains goes to a battery charger which rectifies and drops it to 24v which charges some batteries. This DC is then fed to an inverter which produces a smooth constant 230v 50Hz for the comms kit.
          It looks to me as if your batteries are very small, and I would think that if you substitute even ordinary car batteries, it would make a huge improvement. I guess they are small because the CCTV doesn't take a lot of current. Before installing large batteries you had better check that the charging circuitry of the UPS is capable of providing sufficient capacity to charge the batteries. Those ones from what I can see look like regular fire alarm / burglar alarm batteries.
          Happiness is wanting what you have got.

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