Battery backup for t'other halves computer

Discussion in 'Electricians' Talk' started by BikerChris, Aug 15, 2022.

  1. BikerChris

    BikerChris Active Member

    Hey all,

    Sorry to ask this, just thought I'd check. sorry again for it being long, welcome corrections.

    We had some power cuts the other day and missus got the a hole cos she couldnt work on her computer. I bought this UPS for her ages ago and it does well to protect her computer, gives a few mins before it auto shuts down, clever that.


    Anyway, there are times when she could do with more time than just 10 minutes (in many ways lol), so I bought one of these a while back, thinking I could buy a deep cell battery and just have it to give her a good few hours.


    Anyway, finally on to getting the expensive bit, the battery and went hunting for info, which started with how long it needs to run. I measured it and its around 200W, so figured she'd be well happy with 4 hours use. I checked the most dangerous thing on the planet, youtube and it said:

    W (200) x hours (4) gives 800WH

    A 12V 100AH battery has 12x100 = 1200WH...but deep cell can only be discharged half the capacity, which makes it 600WH. Oh well, 3 hours might be enough.

    So question is, is anything I've done right? And where's a good place to buy one from?

    Cheers in advance,

  2. FlyByNight

    FlyByNight Screwfix Select

    It that 200w continuous? And does it include screen/monitor?

    Your calcs are right but fail to take into account the 85% efficiency. May also be work looking at the computer - does it have a 100-250v input range which may give a better choice of inverters.

    Or does the PC have a separate power supply? If so, so manufacturers, Dell for example, make a 12v to PC voltage supply for their laptops - some of which can be very power hungry.
    BikerChris likes this.
  3. FlyByNight

    FlyByNight Screwfix Select

    As for batteries, look at Yuasa - some of teh best sealed lead acid on te market. Do you want a 100AH battery - it will be massive, or would several smaller such as 17AH be easier to handle?
    BikerChris likes this.
  4. BikerChris

    BikerChris Active Member

    Thank you for this mate, Yes the 200w was peak computer, speakers, monitor and a little label printer she has.

    I didn't know about the efficency bit, the computer is just a normal upright one and has a 550w PSU, can't see any options for the voltage range.

    2020-10-08 20.08.28 - Copy.jpg

    at the moment, I plug all the things into the ups, I am guessing that laptops are more 12v friendly may be? her one just uses a kettle plug.

    i hope this is handy info?
  5. BikerChris

    BikerChris Active Member

    thank you again, yeah I like Yuasa and use them in motorbikes all the time.
    I'm alright with one 100AH as I'm alright to lug it about, plus it will be less faff with connecting and re-connecting cables.

    I figure that I could have the battery under her desk (far away from feet, if that is safe) next to the UPS, and when we have a power cut, she unplugs the ups from the wall socket and plugs it into the inverter that is connected to the battery.
  6. FlyByNight

    FlyByNight Screwfix Select

    You are stuck with an inverter - tell her that if/when it happens to turn off the speakers, minimise printer use ...

    Also have a look at dedicated PC UPSs - they are designed to be in circuit all the time and auto switch when required
    BikerChris likes this.
  7. BikerChris

    BikerChris Active Member

    ah, well at least I already have it. I will let her know about the speakers and printer, it will let the computer work for longer (which means I get less in the ear)

    thank you again mate
  8. FlyByNight

    FlyByNight Screwfix Select

  9. Hans_25

    Hans_25 Screwfix Select

    You might be better off buying something designed for the job, I have this UPS APC Back-UPS BX750MI 750VA UPS, | costs £92.

    Or there's a bigger version for £139 APC Back-UPS BX1600MI 1600VA UPS, |

    Have set it up in my "data centre" so that when power goes off it continues to power the NAS (a DS920+), which then powers down after 15 mins in a controlled way. It also powers the router, phone, wifi access point etc so I should (in theory) have broadband and telephone for a few hours.

    ElecCEng and BikerChris like this.
  10. Bazza-spark

    Bazza-spark Screwfix Select

    That may be the case, but if a cell fails you have no power until you get a replacement battery. With multiple batteries, if a cell fails you can remove the faulty unit and keep going albeit on a reduced power.

    Just something to think about, depends how important it is.
    BikerChris likes this.
  11. vrDrew63

    vrDrew63 Active Member

    Fortunately we live in a country where interruptions to the power supply, when they happen, rarely last for more than a minute or two. A power cut lasting for hours at a time would seem to be extremely rare, and would only come about as a result of a natural disaster, or some major industrial incident.

    That might happen, but it seems unrealistic to expect office work to go on as normal under the circumstances. For truly vital functions (like powering hospital equipment or emergency services radio equipment) then a backup generator seems - to me at least - a more practical solution.

    In my personal experience, I tend to be the source of most of the "power cuts" I have to deal with. Flipping the "down sockets" breaker in the Consumer Unit cuts power to the router and satellite box, which typically then need to go through a 5-10 minute reboot process. Inconvenient, but not the end of the world.

    A UPS that gave a user a ten-minute window to save whatever they were working on, and go ahead with an orderly shut-down of their computers, would seem to me to be an ideal solution. Extending that time period out to a matter of hours looks like it involves cost and complexity that has passed the point of diminishing returns.
    BikerChris likes this.
  12. quasar9

    quasar9 Screwfix Select

    You said, “I didn't know about the efficency bit, the computer is just a normal upright one and has a 550w PSU, can't see any options for the voltage range.”

    it’s hardly a “normal” upright one ! Looks like a gaming version with liquid cooling of CPU. like a sports cars, these are built for speed rather than petrol economy .

    power used with modern CPU varies with workload, although very few are remotely stressed by office work. You need to run a game with high refresh rate and computational power to stress both the CPU, GPU and main storage when demand for power will be highest.

    when you buy, make sure that the software that UPS runs and its partner app is compatible with the OS you are running. Good ones msg the PC to start winding up and save everything to hard disk/SSD when the battery is coming up to exhaustion point.
    BikerChris likes this.
  13. Hans_25

    Hans_25 Screwfix Select

    Like the ones I referenced above - they have a USB lead that plugs into the PC/NAS etc to sync with the app software.
  14. MGW

    MGW Screwfix Select

    You have an ups, so if the computer runs from the UPS then in turn the UPS can run from mains or the inverter so she has the time the ups will keep computer running to switch on inverter and swap plug from mains to inverter.

    I use a simple laptop, so with a power cut I can plug into the power bank an only one some thing like this [​IMG]but that does not help with router, I could use a second inverter for router, however although it works now, don't know for how much longer.

    My friend went onto fibre, and he was careful to get a back-up version of router that will continue to work with power cut, but the OpenReach box down the road doesn't so a power cut still no internet, so only mobile phone if the mobile phone will work.

    I had a battery powered router, well still have router, but no longer have an active sim in it, however the lap top would auto swap with a power failure from sky hard wired router to EE mobile router.

    But the main thing is how important is it to continue to use internet with a power failure, and is not the mobile phone good enough?
    BikerChris likes this.
  15. Hans_25

    Hans_25 Screwfix Select

    Power cut will likely cut power from local mobile masts so no mobile signal either.
    BikerChris and MGW like this.
  16. quasar9

    quasar9 Screwfix Select

    The industries great hope is that 5g and 6g (work on standards etc has already started as the world rolls out 5g ) will make all hardwired internet redundant including fibre, which is still replacing copper in UK.

    the other trend is the CPU and GPU chips. Most manufacturers have been focusing on retaining the current levels of performance while continuously reducing the average power consumption. Some experimental chips from IBM have transistors only a few dozen atoms wide.

    only the battery manufactures are still struggling in terms of new direction. Although there are many “new technologies” on the horizon (including purportedly, a battery made from nuclear waste and synthetic diamond wafer that lasts for a hundred years in use ) old lithium is still the king.

    all said the future is mobile and battery powered so power cuts won’t be an issue for many. In fact even now, mobile battery driven technology has taken off in countries with unreliable power supply . However, for the UK at least in the near terms, the lack of investment and planning will mean more power cuts in the future so maybe an investment in a UPS is a wise move.
    BikerChris likes this.
  17. MGW

    MGW Screwfix Select

    Earlier this year in the high winds, the local EE mast was damaged and failed, the result was my central heating started to play up, the wall thermostat has a built in PIR, so every time I walked past it, the heating went to comfort temperature, not worked out for how long, but because my mobile phone was not seen as being at home, even though it was, the central heating wall thermostat thought I was not home so went to eco mode/temperature.

    I have now turned geofencing off, but power cuts affect the internet so the computer back up only needs to be long enough to shut the computer down in most cases. OK I did use packet radio, so that did not fail due to power cut, but my radio, and modem/TNC (terminal node controller) were also 12 volt, so the 110 amp hour leisure battery would run them for some time.

    The Amiga A1200 would reboot fast, so it was a simple unplug from mains socket, and plug into inverter, it did not seem to mind loosing power.

    I was sorting through my stuff a couple of days ago and found a 120 volt 60 Hz UPS, it must have been left unused for some time, I do remember powering it up from a 110 volt 50 Hz transformer, but likely some 5 years ago, so I looked to see what battery was fitted.

    I found a VRLA battery of around 7 Ah connected with spade connectors, so out of interest removed and put in parallel with a 12 Ah VRLA which is on a smart charger to see if it will charge, unlikely, but an experiment.

    However as said it uses simple spade connectors, and the battery is in a compartment isolated from the rest of the UPS, so in theory nothing stopping me from leaving the battery compartment open and connecting to the AGM 90 Ah battery removed from my wife's car.

    And all my PC's have the option to run off 120 volt 60 Hz, so could use it. Only problem is lack of USA plugs.

    It may be possible to do same with your UPS?
    BikerChris likes this.
  18. vrDrew63

    vrDrew63 Active Member

    You can buy US-spec three-pin power cords here in the UK.

    One of the lesser-appreciated benefits of globalisation is the ability of many consumer electronics to run on a range of voltages and AC frequencies. Obviously it doesn't make sense for Samsung, or Lenovo, or Apple etc. to engineer completely different TVs, computers, printers, etc. for each different market. Most of the time it simply means providing the correct plug. Of which I think there currently eight different types in use around the world. Apparently the current UK wall plug is considered the best - at least from a safety standpoint. As long as you don't stand on the prongs in the middle of the night.
    BikerChris likes this.
  19. MGW

    MGW Screwfix Select

    I think we have had tapped transformers for years, even in the 50's you could select the voltage, some TV's used a large resistor to drop the voltage, but computers were in early days often a kit of parts, people would talk about building computers, where they would select the power supply, processor, mother board and cards to get the output and inputs they wanted.

    There were some ready built units, the Amiga etc, but even they could have hard drives fitted, external hard drives, etc added.

    Today the laptop tends to come as one complete unit, one may add a second screen, or mouse, or external hard drive, but it comes as one unit, complete with battery back-up, so with a power failure you have around an hour or more to find an alternative supply.

    If worried about power cuts, one would use a laptop, we can use an UPS with a desk top, but the need to use desk tops has evaporated as the laptops improved, unless doing some special functions, photography for example. Internet functions are limited by the internet speed, so with maybe the exception of bit coin thing what ever that is, most internet use does not need a fast computer even the one built into modern TV's is fast enough to watch films on the internet.

    There are exceptions, I know on the Falklands using radio links people could want to run there computers outside the times when the farm generator was running, but in the UK in the main power cuts are rare, and normally only for an hour or two, with longer power cuts only option is really a generator, OK an EV can it seems supply power, but if I want emergency power for more than an hour then looking at a generator.

    I would be more worried about power to my central heating than power to a computer, I have an open fire, and some wood, so could keep warm, but with the change in the law over use of diesel, today it would be a inverter petrol generator for an emergency.

    With some thing like the Falklands were the generator only runs twice a day, then maybe using a battery system would work better, but would be looking at Nickel batteries not lead acid, as lead acid take too long to recharge.
  20. BikerChris

    BikerChris Active Member

    Sorry all for delay, work called and I needed the money.

    Thanks for that, I'd like to use what I've got if poss.

    Wow that setup looks clever, nice one! I'd really like to use what I got if possible, if one bit doesn't work, then I'd be OK with replacing it. I've got a half way OK set up, PoE switches are connected to UPS, so that takes care of wifi. I would like to get the UPS to cover the router as well (I've got same one as you, plusnet), but the UPS I've got doesn't have 3 pin outlets :(

    That's a really good point, I had not thought about that. May be I can get a few 30-40A batteries instead of one big one. Cheers for that bazza.

    Cheers drew, yeah our last powercut lasted around 2 hours, its alright if the work she's doing isn't important, but sometimes it is.

    yeah you could be right there, it is probably not cost effective, it's really just to keep the flack away from me when it happens!

    Yeah it was one she was given, it's not bad on the balanced mode though, only sucks around 40W and goes up to 80-90W when being used. She mainly uses it with a virtual machine that is at her work place, she shares the screen with it and uses it like she's at her office desk (that she no longer has lol!).
    Already bought the UPS, seems good so far and has the USB cable that shuts it down safely if there's no power for so much time.

    Yeah that's exactly how I was hoping to use, just unplug UPS from wall and plug into inverter.

    Until I get the router on a UPS, she's alright with hot spotting her mobile phone and wirelessly connecting to that, if she needs t'internet.

    Like you say, if the mobile phone is good enough, that keeps things simple for me and avoids having to buy more tech stuff. Battery powered router sounds good, I've got the plus net one and it's OK, but I do have a spare in case it goes pop.

    That's a fair point, I can't remember what happened last time, think it still worked OK and the last powercut just affected res houses.

    Yeah I have heard about that, I do wonder if it will make fibre redundant, when I have hooked her up to mobile internet (4G I think), the reaction time is really bad compared with fibre, not sure if that is something that they would improve on.

    well we'll see about battery tech eh, would be nice if it got better.

    Good point about future power cuts may be happening more often, might even get myself some batteries so I can charge phones and use my laptop and stuff when needed.

    Wow, to think your heating is mucked up with lack of t'internet, that's bad, but I guess that's more clever tech going a bit wrong and not knowing where you are. shame it does not use bluetooth or something, but I guess that would get complicated.

    I did read thoroughly everything that you wrote, all very interesting stuff, yes may be the UPS could have run from an external big battery and I guess that would save the unplug faff. If brave, I might look into that more, cheers!

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