Beef Up Your UPS

[Surferdude] was unhappy with the decreasing life of his aging uninterruptible power supply. He decided to beef it up using marine batteries. He extended the battery connections outside of the UPS case using #10 wire and swapped the two 12 volt gel cells with the heavy duty lead-acid batteries. Doing so upgraded the device from 20 amp-hours to 84 amp-hours at a cost of about $160. If you’re thinking about taking this on yourself, pay attention to the countinuous output rating of your UPS to prevent a fire risk.

54 thoughts on “Beef Up Your UPS

  1. ugh… instructables… no thanks, not clicking.

    I’m really unimpressed with ‘ibles lately, they’ve been crippling the site unless you pay them money.. to the point where you can’t effectively read the articles, even if *you* wrote them.

    I deleted all my articles there once they started forcing people to pay them to read my articles that I licensed as CC-NC-AT. That shit’s just not right. If they want to charge for my free content they’d better fucking well start paying me.

  2. I did the same thing at my office, except i mounted mine on the wall along with the network hub and fiber optic center. we actually had a power outage and ours kept 3 pcs and monitors up for about 5 hours along with our phone system. its a great setup.

  3. those look to be of too small a gauge to be able to safely extend the battery life – should not have a computer plugged into that. Also, wired in series? fairly sure most ups use 12v.

  4. LOL. If you think that’s cool, check out my UPS revamp! I’ve gotten HOURS of uptime out of it, and the ups is rated for 30 amps, and today sits in my basement, hardwired. I’ve also since made some corrugated plastic covers to keep anything from touching the tops of the batteries by accident.

    The cable I used is 6 gague, which was thicker than the cable used internally as designed by APC, and there’s 100 Amp fuses in line. Each of those copper lugs was soldered on with a vice and blowtorch. The two serial sets of batteries in the pics are themselves used in serial by the UPS for 48v@100A.

    Cables tucked away nice and tidy:
    Whole System:

  5. Most good ups systems use 24 volts so he has done that part right. But as a radio station engineer who did this back in the 90’s you MUST use AGM batteries. The charging circuits in the ups are not designed to charge flooded lead acid batteries so they will over charge and dry out very fast. Bubbling sulfuric acid all over every thing is not a good thing.

  6. Its ok Zigzag… They will learn when the diodes in the charging circuit blow up.. Good luck with the 84 amp hours going through 10 gauge wire lol! its only meant for very short distances at that amperage… I wonder what would happen If you touched the negative side of the exposed battery terminal with your hand and touched your computer case?

  7. @bill hates

    84 Amp Hours =/= 84 Amps. 84 AH simply means it can provide 1A of current for 84 hours OR 84 A current for 1 hour. The UPS isn’t going to be drawing any more power than it would with the old batteries so the actual current (amps) does not increase. The higher AH rating just means that these batteries will last much longer than the old ones on a charge.

  8. are you guys confused or something? almost all UPSes i’ve encountered use lead acid batteries internally. Maybe these aren’t sealed, but they’re still lead acid. The chargers in them are typically fairly dumb low rate float chargers, and unless the external batteries are lower capacity than the internal batteries, there is very low chance that you’ll fry anything.

    This will not improve the power capacity of your UPS, but will increase the amount of time you can run whatever’s connected to the UPS before the power goes out. Most likely (I’d imagine) the power capacity of your UPS is limited by the power transistors and not the battery power capacity. If it were limited by battery power capacity, then hell, it probably has a pretty good chance of blowing up without the mod anyway.

  9. Noticed that this ios for a UPS with two internal batteries. Seems like a dumb question, but for my old one, which only ran off one battery, can I just run it off a single marine battery?

  10. scrap last post, just saw the 24v part on his post. Looks like that’s 30$ I can save on buying a new battery, since I have a good marine battery out in the garage somewhere.

  11. I see that people have no clue about batteries.
    AGM is a lead acid battery. But it is what they call starved electrolyte battery with vastly different charge characteristics, educate your selves and even give it a try, I design charge controllers for solar cell systems which can use lead acid OR AGM batteries there is a huge difference in the float voltage required to maintain a charge. Too much voltage and you over heat your batteries and dry them out.

  12. Almost all low-end UPS’s use cheap sealed immersed lead-acid batteries, so no need for AGM batteries. I did this ages ago and learned not all cheap UPS’s can withstand the extended run time. Wiped out two UPS’s doing this (inverter overheated). Cheap UPS’s not designed for long run-time typically don’t have any over-temperature protection.

    I agree, instructables has gone down the toilet. They want my Email address soooooo bad. Evil lurking.

  13. Yeah, instructables has gone downhill. I remember not having to register for any reason. Then goes “All steps on one page”. Now its practically useless without registration, unless there is only one picture in every picture group. (Registration required to switch to the other pictures in the group.)

  14. my advice would be check your local surplus shops and pick up the old telco batteries.. you can get 96 to 100 or more ah battiers for about 50 bucks… they are a few years old.. but are 7 to 10 year battires… much better then the cost of new which is 400 to 600 each.. they are seal gels so its perfect for ups.. i have about 20 or 30 of them running at the moment on diffrent ups at the house and office… and i can find them all the time …

  15. also something else to consider.. if your going to go with a bigger ups. setup a better charging system.. its better to charge each battery on their own.. to keep their life longer..

  16. I agree with the above poster:

    Please BAN Instructables links from hackaday!

    Instructables site is now getting very crippled. It’s not even possible to click on images to view it in a middle size, you get popups that you should go for PRO, PDF download is no longer available for free registration users, etc.

    The whole site is getting really unusable.

  17. Not sure why everyone is ragging on instructables. I’ve been a member for years, and even with the changes I don’t see anything that has crippled the service. Sure if you want to view the entire ‘ible on one page you need to sign in, but that was in place before they were requesting donations. If it’s a matter of not wanting to give your email, make up one in yahoo, gmail or any of the other free email services. how lazy have we become that you’ll boycott a site with good content just because you don’t want to register. O.o

  18. the quality of articles on hackaday and makezine has gone down the toilet.

    This is a stupid thing to do. The charger in your UPS will not be able to keep up (higher AH = higher charging current). Either the UPS will get damaged, or the cells will be undercharged and their life reduced.

    1. It will just take more to charge them, i’ve been running a liebert powersure 400 with car battery for years, and i had also 10 hours outages, what’s most important is that you run it at most at 1/2 of it’s rated output( or inverter/transformer may overheat ), and that you check that battery voltage does not go above 13.5 volts for 12 volt flooded cell battery , or it will start to produce serious amounts of hydrogen

  19. thats a great idea but sealed batteries would be a better choice (IE: no hydrogen emanations, no leaks, no need to check water level once or twice a year) kinda like the stock batteries you found in ups except more than 7 amps but its a bit more pricey.

  20. I’ve done the same thing, the 5Ah SLA battery in my UPS died so I hooked up my 70Ah SLA battery instead :) I also connected a car charger to the battery to power my Eee, so it means I can switch off my main PC which uses 20x the power of the Eee.
    Now all I need is a UPS my ADSL router likes, it will only work with a pure sine wave :(
    No idea how long it’ll power my main PC because cCome to think of it since I got my 70Ah battery I haven’t actually run it flat or even half-flat yet, I suppose that’s a good thing, longer life ‘n all.

    BTW, Systm did a show on replacing your UPS battery with a larger one in March this year –

  21. Reading this thread has really made me wonder about today’s readership of HackADay…. There is a lot of inaccurate information above.

    Most of it is very unsafe and can get someone hurt. The only one with any accurate information is wulfman; everyone else is pulling crap out of their rear that isn’t anywhere near being right.

  22. >This is a stupid thing to do.
    >The charger in your UPS will not…

    That, and you can usually Ebay used 2u rackmount UPS’s very cheaply. Since the whole global economic meltdown there has been lots and lots of this equipment coming up on the ‘bay for not much dollar. Any “IT” worker has ample opportunitys to liberate this gear too.

    I’ve seen a proper, 5’x3’x3’ free standing, ups catch fire and start melting down inside a datacentre.. good times!

  23. I have a 6kw double-conversion inverter that runs most of my house (double-conversion = everything runs on the inverter all the time). I did this upgrade back in October. Added 16 deep-cycle batteries, giving me 22kw in the battery bank vs. the original sealed batts that only had a few thousand watts. One recent test ran most of my house normally for 17 hours.

    Don’t worry about the charging circuit, it will just charge the new batts more slowly – which will extend their life. And if you do this to the cheap inverters just add a fan or two to prevent the melt-down. Not hard for this crowd.

  24. This works just fine for me.

    I’ve been doing this for 2 or 3 years with a Tripplite Internet350U which, I guess is a 350VA ups. I use it to keep car batteries charged on vehicles which are not currently in service. This is helpful because it keeps the batteries at a healthy state of charge.

    Instead of 4 or 5 minutes run time I can power my computer, monitor, modem and router hub for over an hour and a half which will get me through most power outages.

    Apparently the charger is a constant current source which shuts off at 13.90VDC and comes back on at 13.65VDC. When only charging one car battery it is hard to see the ramp with a cheap DVM, because it’s pretty quick. However when charging 2 car batteries and a motorcycle battery, the on/off cycle takes 5 or 10 seconds, and it can’t keep up with a third car battery: it never reaches 13.9VDC to shut off the charge current.

    I got the idea off the internet – I thought it was right here?? – some article about a franken-ups.

  25. And I forgot to mention that you may be able to get a ‘dead’ ups for nothing, or next to it, because a lot of companies or individuals throw them out when the battery gives out, instead of buying them a new $40 battery.

    I talked to a guy at the battery shop who says he and all his buddies and co-workers get lots of these things given to them, and all they need is a battery.

    A tired car battery and you’re all set.

  26. go with a rack mount or UPS that already has connectors on it for extra battery packs. The reason is that the smaller ups are not designed for long run times and heat builds up. I have used external batteries for a long time with ups. Local school auctions have the large 2200watt rack mounts on auction routinely for $75 a pallet with about 10 of them, all work, just weak batteries.

  27. Ok seriously- lots of stupidity here.

    Most UPS’s are designed to run for a few minutes- the duration of the stock battery. The components (the power transistors and such) are selected to keep cost down and there is usually little spare capacity. Translation? Run them too long and they will burn up, overheat, and possibly cause damage.

    What about charging the batteries? Almost every single APC UPS I’ve seen has overcharged and cooked the batteries inside (go ahead- open any old APC and the batteries will be distended from excess gas produced while overcharging). That may not be important with a $20 SLA battery from Home Depot- but you probably don’t want to do that with a high end telco battery.

    Also, when the batteries are discharged, the charging current required to charge them is very high. (Charing rate/current is controlled by voltage- if the charge controller can’t drop low enough the current will be too high). That’s especially true with deep cycle batteries that are heavily discharged. These batteries end up looking like a dead short to the charging circuitry. If the charger is smart (no ups I’ve worked with has ever had decent charge circuitry) then it will carefully control the charge profile to keep things safe (assuming it knows what type of battery it is charging- it probably doesn’t). Instead- the average UPS is going to put out too much current and burn itself, or the battery, up. It may not happen the first time, but it will happen. The odds of it happening go up significantly the more drained the battery is. For those of you doing this- don’t let the battery run down or you can run into problems.

    If you insist on doing this- make sure you use an extended run UPS, extra large wires (the small size wire used inside a UPS is only for the short runs they have- do not use anything that small to connect external batteries), and for the love of god- keep it outside the house (or at the very least on a concrete floor in a basement).

    Some day I will document my extended run UPS. All my components are DC so I built a 48 volt system with my own smart charge controller and dc-dc converters on the output to power my wireless router, pbx, switch, etc. No Ac-DC-ac-dc conversions. just ac-dc and that’s it.

  28. @Mark Richards: Oh dear god I’m glad you’re not my neighbour. You are so clearly incompetent that you could not possibly built anything safe and functional. You describe a profoundly dangerous literal, time bomb. Don’t you dare, ever try to do anything yourself because you’re clearly incapable. Immediately surrender you real name and address so I can report you to your city electrical inspector to have your power cut off, and get you imprisoned.

    I on the other hand have a completely self build UPS powering multiple DC levels, and 120v and over 300 120v Amps continuous with a measured four day uptime before voltage in the main array drops to 80%. Certainly long enough before my four natural gas, and two diesel generators to start, and they can produce. I even got it UL certified you fucking tool. If you don’t have three separate, hermetically isolated vaults of batteries, you’re clearly not playing for keeps.

    Your setup is clearly shit, and you should eat shit and die you fool. oh yeah. My penis is larger than yours too!

  29. Or just get yourself an RV inverter/charger and setup an even better UPS with near perfect sine wave and a battery the size you determine. Gonna cost more up front, but it works great. I have a Xantrex Prosine 3k with 7kwh of deep cycle batteries (outside & vented) to run the office. I also have that charged by solar, so the office computers are basically powered by the sun and when the lights go out in the neighborhood I’m the only one with lights and TV. Whenever the solar power isn’t enough I just hit a switch and it starts taking power from the public utility.

  30. So I took the plunge and did this myself
    I had an APC smart ups 1500 tower which had dead batteries
    I bought 2 Su-kam 100ah sealed lead acid deep cycle solar batteries to make it 24v

    I then bought the thickest cable and wired it all up
    I’ve been running for 9 months now and its the best thing I’ve ever done
    Here in kenya we get lots of cuts. It will do 24hrs but after 12 hours I have reduce the load by unplugging stuff (usually fridge)
    I power my office and my TV media center, baby monitor, lights etc etc
    The only issue is it takes 24 hrs to get batteries up to full juice
    This particular ups has a fan which I would say is Very important, if your ups doesn’t have a fan,I would buy a 12v silent fan and cut a hole in the case to stop the charging unit from overheating

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