Great Emergency Lights From Not-So-Great UPS

We know your shame. Like you, we wanted to save some scratch and bought the bottom-of-the-range UPS, only to discover that it is no use to man or beast as it lacks the power to perform any reasonable task. It’s now sitting in a corner, to gather dust as its batteries deteriorate.

Not so fast with the UPS abandonment! [rue_mohr] came up with a modification for a small APC UPS that turned it into something a little more useful. Removing the mains inverter from the picture with a few displaced wires and PCB mod, the UPS is now a 12V battery with a mains charger and power outage detection built-in. In this state it’s the perfect power pack for some 12V LED strips used for emergency lighting. There is a handy 3D print that fits the rear socket cut-outs on the US version of the device and provides apertures  for a pair of DC power jacks.

This is a relatively simple hack, but we like it for taking the focus away from the obvious part of the UPS, its mains inverter, and turning to the batteries as the main event. It’s a relatively tiny device, but in the past we’ve featured a UPS at the other end of the scale being used for power back-up to a whole house. Meanwhile we’d like to take a leaf from the [BOFH]’s book, and recommend that the most important piece of infrastructure requiring a UPS is the sysadmin’s coffee machine.

25 thoughts on “Great Emergency Lights From Not-So-Great UPS

  1. Many years ago, the local thrift stores started getting a bunch of usually-dead 12V UPSes and sellimgb them for $5 or less. So I bought them all, reconditioned the batteries (added water, desulphate charged them) and put them into 12V LED strips as well as “fairy lights”. They work great! Just obnoxious with their beeping when power is lost. I should open them and disconnect the buzzers… Anyway, they weren’t hacks but super it is super handy

    1. +1 on this. I decided to measure the battery charge/discharge current in an SL Waber UPS250. I found out the hard way (*BANG!*) that the 12v battery is NOT isolated from the mains! I’ve checked out a few more (APS brand), and found the same thing. The only one that was isolated was an old Sola UPS.

  2. Good idea, I may try it on an UPS I decommissioned a year ago because it kept beeping at me (very obnoxious behavior, don’t care how dire the reason). The fact is, an UPS is supposed to add reliability to an unstable mains supply but in my 40+ years experience, the most unreliable component in any system’s architecture is the UPS. The mains voltage is always more reliable, but then I work in cities where blackouts and brownouts are rare. Also, the batteries have an annoying habit of requiring replacement every two or three years, a ridiculously short period of time, and just buying and disposing of them is difficult in my area. I actually have to pay money to the recycling yards in my city to get rid of them – exchanging them for new ones with the manufacturer is out of the question despite what they may tell you to the contrary in their advertising. If they lasted five or ten years then I might reconsider using them but they don’t, so I won’t. Your city might be different so gauge your need accordingly.

      1. You are lucky. In my city there are recycle shops where you can buy/sell secondhand items but they prefer them to be working and complete with original bits and pieces. If they’re not then they may or may not take them. It’s the independent scrap pickup people who come around in small trucks and ask for a fee to haul away things like old TV sets, bicycles, appliances, etc. I assume that’s because stripping them for metals and parts is how they make their living. Or I can do the disassembly but I must cut the parts into manageable pieces and separate them into categories, then remember to put them out on the few days a year when the exact category is scheduled for pick up. It’s usually easier to just pay the scrappers to haul them away for you.

        1. guess it dpeneds on the local economy, around here (edinburgh, scotland but the uk as a whole is much and such) the council will accept anything for free if its domestic waste. if commercial you can either scrap it yourself and get a few quid, or if its valuable scrap, like batteries and metals you can usually get a free uplift from any of the smaller scrap guys while they do their rounds, i.e. if you cant be bothered with the hassle. Indeed lead batteries are usually in high enough demand most the smaller scrap guys will go door to door around garages and give cash there and then.

          1. Yes but so much for the environment as when you spot something at the tip they wont let you have it.
            Health and safety being the buzzword not recycling.

    1. Re: The batteries going bad every 2-3 years. I got tired of this and did some measurements, I found that a) the batteries are universally the worst bottom-of-the-barrel cheapies the manufacturer can find. b) The chargers univerally suck. In every case, it charged to too high a voltage, did not compensate for temperature or battery age or type, and didn’t know when to quit charging,

      So on my UPS, I hacked them to drop the float voltage to 13.5v. I switched to bigger premium Hawker/Enersys AGMs (G12v13Ah10EP on two, SBS60 on one). I added a fan (controlled by a bimetal snap switch) so the inverter doesn’t overheat, to get full use of the extra battery capacity. I’ve done this to three of them, and the batteries are now 7-10 years old and still working!

      1. That seems like so much work to convert a marginal UPS into something usable. “It’s great, just replace everything except the case!”

        It seems like there should be some kind of project to build The Absolute Best Open-Source UPS We Can Design, based around e.g. “go buy a car battery and clip on these ridiculously over-engineered PCBs”.

          1. In the past, I’ve considered using a old UPS to be an inverter for use in an automobile.
            But first, I needed to find one that was
            1. Free
            2, Used a 12 backup battery.

  3. I recently discovered that those LED strips are popular in the cannibals community as cheap grow lights. A few weeks ago I found what must have been three rolls of LEDs mounted on boards powered by a 12VDC 5A brick in someone’s moving trash. I didn’t understand what he was using it for until somebody at a flea market bought them and explained everything.

  4. For years my outdoor work lite system was a pair of halogen lights on on a tripod and a 1.2KW 2 cycle generator. The lights were cheap HF units and the years were hard on them.

    At a hamfest I picked up a pair of big stadium lights with giant 750W incandescent bulbs in them. I never used them like that. They sat around for years in fact waiting for the right amalgamation of things to happen. A few years ago I wound up using them.

    It started when I found a dead as a doornail HF 5 in one jump pack in a trash pile. Among other juicy pieces, it had a little 200W inverter in it. I also scored an old riding lawn mower from a friend. He had just put a new battery in it and it still did not run right (no kidding…) but he had his fill of screwing around with it.

    The last straw was ebay. I hate spending money but once in a while you have to bite the bullet. I bought two base adapters for the fixtures and a pair of 105W (500W incandescent equiv) CFL’s. I had to do a bit of plasma cutting to the collar in the fixtures as the CFL’s were a bit wider than then incandescents down by the neck.

    It turned out to be an amazingly great combination. Bright as all get out and over a couple hours worth of run time, and no glowing hot lamp housings or generator mufflers. And that is a big deal when you want to pack it up for the night. It sucks having to sit around waiting for things to get cool enough to touch and or not light your car/truck on fire if you are using it away from home.

    The setup also runs perfectly on a little 300W 2 cycle generator a friend gave me for those jobs when you really want to burn the midnight oil.

    Oh yea, you can plug them in to 120V and you can plug the little inverter into the car cig lighter too. (with the on board bard battey). At some point the internal battery may discharge enough for it might start taking enough current to pop the cig lighter fuse but that has not happened yet.

    I would do this with LED’s in a heartbeat if they had 500-600W incandescent equivs with mogle or edison bases than were priced in the range of 2 for $20. I am not anti LED, but for now they are pricey in that size.

    I actually did ponder getting a whole bunch of the old 2 lamp Y splitters and putting 7 of them in each housing and using 8 of the 100W led equiv bulbs you can get at the dollar tree but that would not have fit in the fixture.

  5. I have that same UPS. It seems to work fine for me… though all I have it doing is keeping the internet and LAN on when the power goes out, and just recently one of those mini computers that mounts to the back of a monitor.

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