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Anyone made their own UPS?

Discussion in 'Electronics & Electrics' started by Zee, May 26, 2022.

  1. Zee

    Zee Member

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    Hey all - as per title, has anyone here had a go at their own UPS?

    I'm looking to build something that can keep a network going for about 8-12 hours (I've not yet done the measurements, but based on specs, I've got a 150w POE+ switch (so let's say 200w), 4 WAPs that allegedly draw 9w each (though this is obviously drawn from the PoE switch), and an over estimate of 100w for the router. Obviously, these are not going to be the real figures, but it is a good worst case calculation estimate.

    Obviously I'll need a few deep cycle batteries, an inverter of some description, a way to charge them, and a relay (non-mechanical) that will switch power when we lose the mains (this happens often). I don't mind if the batteries charge slowly,

    I'd be curious if anyone has done this, and how you went?

    I know I could buy a commercial UPS, but pricing seems to get insane the second you need it do more than just shut something down within 5 minutes - and I'm not convinced that adding batteries (externally) to a commercial UPS is a good idea.

    Note - Electrical connections would be performed by a qualified electrician, I personally hold an open cabling license (though this will be done in another country, so a moot point) and I do have a background in electrical engineering -which that is something I studied about 20 years ago, though this is very basic stuff overall (calculations wise) and it's really just the hardware options I'm looking for.

    Thanks,

    Z...
     
    Last edited: May 27, 2022
  2. fnp

    fnp Member

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    Daniel Rutter did, about a billion years ago. Some of the gear might be a bit out of date but power is power and that thing had to power a CRT monitor.
     
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  3. bonox

    bonox Member

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    an automatic transfer switch i think is what you're looking for to get the ball rolling. The fun will come if you want the inverter online all the time or on standby. If you want online all the time, you won't need the ATS but you'll need a big battery charger. You've got a 236 watt load plus losses, power factor etc. If you say 275W you're looking at a 12V 25A power supply, 24V 13A etc. Those are pretty bulky units. A sinewave inverter on the other hand is pretty cheap at those currents, but 2750 watthours is at least three 100aH 12V batteries going almost dead flat. More would be better - probably 2s2p and a 24V inverter. Guessing it's not AUS given all your locations, but if it were here, i'd be looking for a used dumb(ish) UPS with expansion capability and just plugging more battery into it if you don't care about the recharge time. There are quite a few on gumtree around here for not crazy money that support up to four additional battery sleds, so they're definately intended for extended runtime (normally of much higher power though) so the charger in the unit is likely to cope. Probably much cheaper than a build your own. Might also need to disable the warning speaker if you legitimately want it to run for ten hours though.

    On the other hand, if all that gear can accept a 12V DC (or 13.8V better) input, just find a charger with float capability of 12V 30A/24V 15A etc (higher than the standby inverter option because you want to power the gear plus charge the batteries after they discharge), build a battery and run everything online all the time. If it has to be 12V regulated, then add a beefy regulator board to the mix. Might be able to find what the switch wants online, but it's probably something like 12V inside if you want to bypass the AC input.

    I would consider a 12V to 13.8V high current regulator like this
    https://www.powerstream.com/dc2.htm
    and power the thing using a 500W ish computer PSU (500ish output on the 12V rail of course). Power the
     
    Last edited: May 26, 2022
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  4. cozbert

    cozbert Member

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  5. Current

    Current Member

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  6. OP
    OP
    Zee

    Zee Member

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    This would be ideal - were this for Aus, but the market I'm in (Philippines) is ridiculously expensive for electronics (they are still trying to flog 4th gen i3's at Aussie 12th i5 gen prices in many cases), and that's assuming you can find a quality brand. Having said that, buying a unit used locally, removing the battery and buying batteries there is not an entirely silly idea - especially if it can support 4 additional battery sleds. I'll investigate my options further with this.
    [most of the gear has 240v 3 pin sockets, sadly.
    This is also not a half bad option. Solar is something we are looking at to reduce our reliance on the (very over stressed) grid, and long term, we'd like enough power to be able to run essential light, the fridge and the net for when we lose power for several days (typhoons have been known to knock power out for days on end in some cases). Feed back in to the grid is not an issue, since that level of sophistication is probably decades away where we are...

    Anyway, this is also an option I'll look deeper in to.

    Z...
     
  7. bryn

    bryn Member

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    Look at a Victron Multiplus, for example- its an inverter, battery charger and ATS all in one, with BYO batteries. Can be multi-chassis parallel-ed for 3 phase or more capacity.

    Cheaper brands exist of similar ideas, but IMO Victron is one of the best, from a reliability and support perspective.
     
  8. bonox

    bonox Member

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    not really what I meant. It's all 240V source one way or another - it was a question of whether you're willing to open the case and find out what the output of the psu behind the 3 pin socket is. Then perhaps put a barrel socket or similar into the case and power it by DC direct from the battery which would avoid an inverter altogether and a bunch of losses associated with it.

    The switch is possibly the most complicated here since they can take 12 to 48v output in the ethernet side, but if you're only plugging 12v stuff into the switch then it gets simple again. What model are you using if you want to investigate this path?

    I love that victron multiplus for a project I have in mind though.
     
  9. Pugs

    Pugs Member

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    You probably need multiple options of Days of off grid reliability.

    Solar and Battery for that. Maybe add a wind collection system aswell

    Generator and fuel supply.
     
  10. speedcrop

    speedcrop Member

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  11. cvidler

    cvidler Member

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    avoid the SOHO style commercial units they're built down to a price. Adding batteries is a non-issue to commercial* units - many are in fact designed for it. And when looking at the price consider the fact a UPS is a long term investment, they last forever, you're not replacing them every couple of years like you would PC components. with that in mind be sure you upspec your UPS to cover future and unconsidered increases in load. buying a bigger UPS now is better than having to buy a bigger one later.

    I'd suggest avoiding a DIY approach, you'll miss out on some important features the commercial ones have (remote monitoring, safety features, properly engineered/integrated components), that'd you'd not be able to replicate for less $.


    What I do suggest however, is don't buy the name-brand replacement batteries, they seem to be priced as if they're worth their weight in gold. having run large-ish UPSs (I've got 9KVa capacity across 3 units currently) myself for decades, the name-brand batteries and the deep-cycle ones you can get for half the price locally all die after ~3 years and have the same run times anyway.


    * look for name brand rack mount style units. e..g MGE, APC, Schneider, Eaton.
     
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  12. 1800-gumby

    1800-gumby Member

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    I work with this stuff in remote environments and depending on what you're doing going full dc saves you a fortune in battery capacity due to the terrible standby efficiency on most inverters.

    You can get 24vdc POE switches and most modems can have their plug pack replaced by a dc to dc converter. Get a basic power data logger and run your system through it on a plug pack for 24hours and get a real idea of load.

    250w is a lot, to give you an idea, over the last 7 days my family of 4 has averaged 230.1w on one GPO circuit and 139w on the other. That's the whole house load include a clothes drier, coffee machine etc.

    An off-grid solar hybrid inverter will be the best option to do the lot if you really need 250w. But if you can bring the load down a pair of 100ah lead acids and a decent size charger and dc to dc regulator will do everything you need.
     

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