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UPS Hacking in Hurricane Season?

Posted by Cliff on from the changes-for-extra-survivability dept.

kengreenebaum asks: "Perhaps not the most exciting of topic; however it is storm season and I have a couple of UPS's that need new batteries. What is the best source for high quality, long lived replacement batteries for these devices? I assume it takes a special chemistry to survive continuous trickle charging and an occasional deep cycle. Has anybody tried connecting larger capacity batteries external to the UPS enclosure to attempt longer run times? (Obviously the load capacity is based on the inverter itself and can't easily be modified) Also what software do you use for monitoring and automatic shutdown on Linux? I have collected quite a few APC and Belkin UPS's 700VA or smaller as they go on rebate/sale."

3 of 62 comments (clear)

  1. Not sure if entire relavent by Student_Tech · · Score: 3, Interesting

    For the batteries, if it is maintaining the voltage at a "float voltage" the batteries can be held nearly indefintly without a discharge or worry of overcharging. Lead acids have a float voltage of about 2.35 volts/cel (based on some quick googling). They will still die after some time.
    But I don't know what technology, size, or how the UPSes actually using the batteries.
    If I was DIY a UPS, I would have about 10 12Volt batteries (no transformers...), drive them off a full-wave rectifier, filter the power from the rectifier a bit, and then invert the power to make it back to AC and use my equipment off that. Advantage, I am always off the batteries, disadvantage, I have no monitoring ability and if I was to set the incoming voltage to the float voltage, it will probably take a while to charge.

    1. Re:Not sure if entire relavent by spikestabber · · Score: 4, Interesting

      I've ran computer switching power supplies off of 110V DC (Direct current) before. Since their internal switching unit does not need the alternating current anyways. The AC is just converted to DC and filtered with a couple large capacitors, so feeding it DC will work just fine.

  2. Re:UPS' Contain Standard Gel / Sealed Batteries by nuxx · · Score: 4, Interesting

    Here's the thing... I *think* you could, but unless you properly take into account the amperage of the batteries and such, you could risk damage to the circuitry which handles the switching. And that would be bad...

    That reminds me of how once when working retail, this guy came in and asked me how many deep cycle batteries he could chain off an APC BackUPS. He wanted literally racks and racks of them, so that he could handle his whole house. All while having things switched by that little BackUPS...

    I'm not sure if you've ever been in a server room, but the UPS' to handle switching massive loads like this tend to be multiple-rack-sized, having contacts that look more like copper paperback books jutting out of the panel.