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OT: Can a power surge burn out the battery side of a UPS?

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  • #16
    Originally posted by gellfex View Post
    Thanks all, but none of those dead battery ideas explain why it would now not power up that side of the circuit now that line power is normal.
    Dead batteries may in fact explain why the inverter side will not work even with line power on. I have loads of UPS backed PC's in systems where I work. On many of them, once the battery is dead, the front panel will not even light up even though it is powered from the wall and feeding power through to the surge protected outlets. Seems stupid and counter-intuitive, but that's how some of them are made. No idea why, probably so you throw it away and buy an new one when the batteries fail.

    If you want to test the theory and have a suitable DC power supply, try applying 24VDC (or whatever the normal battery voltage is) to the battery terminals and then power it up.Or use a known good battery. There is a good chance that it will act normally.


    • #17
      Our experience at work has been 97% battery, 32% of which is due to dying charging circuitry.
      Dumb things like the rectifier loses a diode, etc.

      Also, if we buy all the UPSs at the same time, a surprising number of those die within a few months of each other.
      It's like they have a defined lifespan. heh.

      And in theory, no, the A/C side should be able to fry everything except the load- side inverter circuitry. In theory.

      In practice, we see them die after an unanticipated power outage when the batteries get flattened.
      (ours just hold up the processing for long enough to protect us from short- term interruptions.
      When the power goes out, the lights go out, and the show stops. If the processing stays up,
      we avoid a lot of reboot time IF we've not been out so long as to dump the house.)

      some things will never be known.
      rusting in Seattle


      • #18
        Well, in the one I just messed with it's definitely the battery. I plugged in another 12v SLA and it worked fine. I put the old one on my smart charger, it read >14v and declared it full in 30 sec. But when I put it back on it would not boot. It seems like it needs enough 12v power to throw the relay that connects them to the AC. I'll check the size on the other and order replacements. The 7ah ones I use on my kayak fishfinder are too big.

        I had no idea these things were such a pain even to pros. I've had them squeal and make a PITA of themselves before when they wanted a new battery, but not this. And to make it even worse, the tiny screw holding the battery compartment slide was a torx! Grrr. At least this one has a slide, one of my others you have to take out 6 screws and take the whole case apart, as if they NEVER need battery service! I wish there were something to do with these batteries, I keep 14 e-lites in service and I end up with a LOT of those 6v SLA batteries!

        Thanks all for your help.
        Last edited by gellfex; 02-23-2021, 12:30 AM.
        Location: Jersey City NJ USA


        • #19
          I recycle the batteries at Lowe's or Home Depot.


          • #20
            One thing that can happen with UPSes is one cell in a battery can suddenly go high resistance. It will seem like it is charged and when it actually does a loaded self test it fails. I have a APC 1kva unit and I have had it happen twice where one cell in one battery goes bad and that takes down the entire UPS. Put a meter on each battery and it looks fine. Put a high wattage resistor across it and it drops to nothing.

            Most scrap yards will actually pay you for batteries. The lead is valuable.