What size inverter?

Discussion in 'Tech/Mech General' started by Encantador, Jul 15, 2014.

  1. Encantador

    Encantador Funster

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    Looking at buying a pure sine wave inverter to run a Intel NUC and a 22in Samsung monitor (mains).

    How would I work out the right size inverter?
    Would it need to be hard wired?
    How long would I be able to run them before risking taking too much out of the batteries (2 x 110v I think).

    Thanks

    Steve
     
  2. jollyrodger

    jollyrodger Funster Life Member

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    We have a "Ring 1000 pro" modified sine wave.
    180w of solar panel up top with 30amp regulator.
    3 auxiliary batteries total 300w
    1 starter battery 100w .
    Solar can charge all of them.
    Have been running via the inverter 2 laptops .22" tv.
    hdmi multi media player .
    .her indoors
    Travel iron .toaster 12v hoover. Not all at once !
    Batteries showing between 12.5v and 14.2v throughout this trip .
    Thought did plug in to ehu at park verger 1 night .
    Otherwise the ring inverter doing a grand job.
     
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  3. geo glasgow

    geo glasgow Read Only Funster

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    there are loads of quality tv screens that run on 12v i would suggest if you dont require an invertor for any other reason than a tv then buy a tv with a 12v adaptor most of us on here i would think run in the same way, however yes i have a large invertor fitted but not for running the tv and satellite but for other reasons, so less work alot less cost and possible a saving.. good luck as you will getgood advice on here ,invertor advice always a favorite on here,, maybe . satellite dish, then solar panels..lol
     
  4. geo glasgow

    geo glasgow Read Only Funster

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  5. jollyrodger

    jollyrodger Funster Life Member

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    Oops batteries that is amps not watts.
    Cheap french plonk !
     
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  6. funflair

    funflair Funster Life Member

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    Hi Steve

    If you only want the inverter for a 240v TV then as others say the better route is a 12v TV, but it is a bit extravagant throwing away a perfectly good TV and Inverters are handy things to have, I guess peoples objection to running the TV on 240v is the power required to simply run the inverter would be around 1 amp and that is before any power is supplied. After the initial amp to run the thing the inverter is then about 90% efficient so you need to know how many amps or watts the equipment requires (amps=watt/volts) I would then want an inverter at least twice this current rating. Then just add up the total watts used by TV etc divide by 12 add 10% and add 1 amp and you are using this every hour for example 200 watts divide by 12 is 16.66 amps plus 10% plus 1 amp is 19.3 amps so for 3 hours would be 58ah which would be a big dent in a 110ah battery bearing in mind if you take 110 amps from a 110ah battery you will kill it also remember if you have say 200 watt of solar this will replenish your batteries in around twice the time it took to flatten them in this example so 3 hours TV needs 6 hours decent sun.

    If you want a quick rule of thump amps required at 240v multiplied by 20 gives you the amps drawn from the 12v supply plus a bit for losses.

    These figures are example only so dont panic your set up may use less power.

    I would say yes hard wire with a fuse.

    Martin
     
  7. John Laidler

    John Laidler Funster

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    The OP wants to run a computer and a monitor, not a TV. A quick google suggests the Nuc uses very little power, about 30W. The monitor is a bit more difficult as models vary but should be less than 50W.

    So you don't need a very big inverter, a 150W model should be ample. I would hard wire it.
     
  8. hilldweller

    hilldweller Funster Life Member

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    So to complete the OP's question.

    80W and he has a theoretical 220Ah or 220 * 12 = 2640Wh. Half that as usual. 1320Wh.
    1320 / 80 = 16.5 hours.

    So absolute maximum is 16 hours with no other electrical use.

    May be much less depending on efficiency of inverter and true battery capacity.

    Next question might be answered by 3 or 4 100W solar panels depending on where and when he expects solar to keep up with that demand.
     
  9. Encantador

    Encantador Funster

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    Thanks for the replies.

    Yes, it is for a computer and monitor, we already have a 12v TV.

    I am looking at a NUC for use as a media centre at home using XBMC. There are cheaper ways of achieving this, I am currently borrowing a Rasberry Pi which is working well.

    Investing in a NUC (as opposed to a Pi) would make more sense if it could be used in the MH as well. I already have a monitor, so the only extra cost is the inverter and fitting.

    I have one solar panel but have no idea what size it is.

    The most I would expect to use it on any one day is probably 3-4 hours, so from the calculations above, that doesn`t seem to be a problem.

    Thanks again for the replies, very informative.

    Steve
     
  10. Wildman

    Wildman Read Only Funster

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    all of the above calculations were based on sole usage by the monitor, it will vary if TV is also used. Power is in Watts (irrespective of voltage) so Watts divided by the voltage will tell you the number of amps per hour it will use.
     
  11. hilldweller

    hilldweller Funster Life Member

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    Spot on so I wonder why batteries are semi-meaningless Ah ?

    If Wh how much less confusing around here.

    So X has a 1320Wh battery wants to run 80W so 1320 / 80 /2 ( the dreaded half empty ) = 8.25 hours.

    Maybe there is a good reason I do not know about.
     
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  12. Wildman

    Wildman Read Only Funster

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    I couldn't agree more Brian it is just an extra order of daft.
     
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  13. John Laidler

    John Laidler Funster

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    As I understand it the Ah rating of a battery is based on a specific test which discharges the battery over a certain set time down to a specified level of discharge. It is not necessarily a good guide to how long a battery will actually last if it is discharged at a very slow or very high rate. For example a 100Ah battery might indeed last 100 hours if you drew 1A from it, but try discharging 100A and it could be flat in 10 minutes, it certainly wouldn't last an hour.

    The Ah figure is just a way of comparing different batteries.
     
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  14. Wildman

    Wildman Read Only Funster

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    and a Watt level battery would do the same thing without us having to explain ohms law every 5 mins.
     
  15. SomeoneElse

    SomeoneElse Funster

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    Tut tut!
    Clearly Ohm's law hasn't been explained enough. It defines the relationship between Volts, Amps and Ohms, IE resistance. Note: no mention of Watts.

    The usual figure quoted is from the 20 hour test. IE a 100AH battery will be discharged at a constant 5 Amps for 20 hours and still maintain a voltage of 10.5V (IE dead flat) The test is also conducted at a constant temperature of 25C.

    Comparing the AH reading of different batteries is only useful when the same testing standard is used. Usually attributed to Grace Hopper "The wonderful thing about standards is that there are so many of them to choose from".
     
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  16. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    I use a Raspberry Pi as a media centre and it will work in the camper too. I added a 1TB USB3 portable HDD for storage and it all powers from the Pi PSU or from my installed USB socket in the camper. Less than £70 off Ebay for the Pi with remote control and £50 ish for the HDD. Size of two packets of fags with the HDD but will provide full 1080p HDMI video output.

    D.
     
  17. cmcardle75

    cmcardle75 Read Only Funster

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    I'd not use an inverter for this. Not the inefficiency, but the noise. Small inverters often have small fans. Small fans are louder than big ones and have particularly annoying frequencies.

    IIRC, NUCs use 19V, so a standard car laptop adapter will likely fit the bill. 12V monitors are easy enough to come by. Just go to a shop and look for monitors that have external bricks. Then check the voltage. This will result in a much quieter set up.
     
  18. cbrookson

    cbrookson Funster

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    I think you will find that the Intel NUC will run off 12 volts - see here for a discussion.
    If you then find a 12 volt screen then all your problems are solved (y) and you will not be draining your batteries quite so much ..........

    Cheers
     
  19. cmcardle75

    cmcardle75 Read Only Funster

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    Wow, even better. The one I use had a 19V power supply, but it looks like you can just shovel 12V into it. The only slight concern is if it drops out completely when the battery drops below 12.0V.
     
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  20. Encantador

    Encantador Funster

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    Thanks again for all the replies.

    Where the monitor needs to be is in the lounge area, the nearest 12v socket (cigarette lighter) is in the cab, the only other one is in the bedroom. The bedroom one is too far and the cab one would require the ignition to be on and obviously uses the engine battery.

    As the monitor would be next to the seat with the batteries beneath it, I assume the best option would be to have another 12v socket of some description wired from the hab batteries.

    Can anyone suggest the best option for doing this that I can then take to a auto electrician?

    The reason I am leaning towards the NUC is that it is a full blown computer. Still don`t understand what I would need to make it work on 12v though. Is it just a seperate power lead, or would it need some internal tinkering?

    Thanks

    Steve
     
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