Which size inverter.

Discussion in 'Solar Power' started by Wildge, Mar 20, 2016.

  1. Wildge

    Wildge Funster

    Joined:
    Jul 24, 2013
    Messages:
    1,131
    Likes Received:
    1,432
    Location:
    Derbyshire
    Have to run a piece of equipment for approx.1 hr x 4 times a day. It's 115-230v....50/60Hz 150watt.
    What size inverter would we need ..? At present have 180w solar and 2x80 batteries.
    Thanks for any help :)
     
  2. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,475
    Likes Received:
    16,947
    Location:
    YO11 2BD
    300 watts will allow it to run cooler than a 150watt version.

    You may struggle replacing 50amps per day even with a 180 w panel....the sun doesnt always shine.
     
    • Thanks Thanks x 1
  3. JeanLuc

    JeanLuc Funster

    Joined:
    Nov 17, 2008
    Messages:
    2,782
    Likes Received:
    1,859
    Location:
    Warwickshire
    As pappajohn says, anything above a 150 watt inverter will suffice but I would allow some headroom so 300 is a good option. Also, before buying one, check whether the equipment is sensitive to wave form. Some items will not run off the cheaper quasi, or modified sine wave inverters and need a pure sine wave (PSW) model. If in doubt, go for a PSW version.

    Your power consumption will be 150 watts divided by 12 volts = 12.5 amps (but you will draw a bit more due to the inverter's inefficiency - say it's 90% efficient) so assume 14 amps;

    x 4 hours per day = 56 amps or 35% of your maximum battery capacity.

    To replace that from the solar panel(s) I would guess you will need around 6+ hours of good sunlight in the 'high' season. Possible between May and September - not practical at other times (unless you are on the Med or North Africa). Either mains hook-up or a generator required between Oct and April/May in UK.
     
    • Like Like x 4
    • Informative Informative x 2
  4. Wildge

    Wildge Funster

    Joined:
    Jul 24, 2013
    Messages:
    1,131
    Likes Received:
    1,432
    Location:
    Derbyshire
    Thanks ... just tried today...that was the reason for the question, already have 300w pure sine wave and when I connect get a load of beeping .....:(
     
  5. sallylillian

    sallylillian Funster Life Member

    Joined:
    Oct 29, 2011
    Messages:
    780
    Likes Received:
    498
    Location:
    Falmouth, Cornwall
    You need to check max load and continuous load on your current unit.
     
  6. Don Quixote

    Don Quixote Funster

    Joined:
    Jul 29, 2012
    Messages:
    2,500
    Likes Received:
    3,697
    Location:
    Lost in La Mancha, Spain
    The "beeping" is because the inverter see the voltage dropping at the batteries and will not work. This tells me that your batteries are below 50% charge and are not up to the job and will soon be dead and unrecoverable. Try a full charge without any load on the batteries for 2 / 3 days then test again.
     
    • Like Like x 1
    • Thanks Thanks x 1
    • Funny Funny x 1
    • Informative Informative x 1
  7. Wildge

    Wildge Funster

    Joined:
    Jul 24, 2013
    Messages:
    1,131
    Likes Received:
    1,432
    Location:
    Derbyshire
    (y) Thanks , away at present will do that on return.
     
  8. CherryPirate

    CherryPirate Funster

    Joined:
    Sep 4, 2013
    Messages:
    154
    Likes Received:
    160
    Location:
    Hants
    I would also investigate whether the manufacturer has a 12v lead available as this might draw less amps overall. There is often one available. I recently bought one from Resmed for my machine for £67.26 including postage.

    Colin
     
    • Like Like x 1
    • Informative Informative x 1
  9. JeanLuc

    JeanLuc Funster

    Joined:
    Nov 17, 2008
    Messages:
    2,782
    Likes Received:
    1,859
    Location:
    Warwickshire
    How is the inverter connected to the batteries? If the cable is not thick enough you will get voltage drop causing the inverter to give a beeping warning. I have a Sterling 150W PSW inverter that came with a cigar lighter connector. When I connected it into a socket fed by standard cable from the Elektroblock and plugged in a MacBook Pro to charge and a small speaker system, it beeped. Once I had wired it directly to the habitation batteries with decent cable the problem went away. Here is my installation if it helps.
    http://www.motorhomefun.co.uk/forum/resources/install-a-small-inverter.17/
     
    • Like Like x 1
    • Informative Informative x 1
  10. Wildge

    Wildge Funster

    Joined:
    Jul 24, 2013
    Messages:
    1,131
    Likes Received:
    1,432
    Location:
    Derbyshire
    Thanks JeanLuc....not very technical I'm afraid . It was installed with the sat. dome and solar panel. Just about to have Hab. Check so will get them to look at it.
    Just pleased you have confirmed, that if everything operating as it should then the machine will work.
    Thanks again.
     
  11. Dorset Diver

    Dorset Diver Funster

    Joined:
    Dec 23, 2014
    Messages:
    368
    Likes Received:
    187
    Location:
    Somerset
    That's interesting. I'm new to using an inverter and I recently tried the one fitted to our MH. 1800w driven by 2 x 85 amp batteries (new). I ran a 1000w kettle until 1.7 ltr of water was boiled. In the first instance there was a lot of beeping and the unit kept cutting out (no power to the kettle). I persisted with resetting it and suddenly it settled down and completed the job. The batteries started at 12.8v dropped to 12.2 in use and then recover to 12.7v as the load switched off. With the aid of the SP on a very grey day they then recovered to 12.8v in about two hours and 13.0v in about four. Does all of that sound reasonable or should I be concerned?
     
  12. Don Quixote

    Don Quixote Funster

    Joined:
    Jul 29, 2012
    Messages:
    2,500
    Likes Received:
    3,697
    Location:
    Lost in La Mancha, Spain
    To be honest your asking too much from your batteries to boil a kettle and will kill them after a period of time. There is no way in two hours you replaced the amps taken out of your batteries in the UK sun. Even in Spain where we live it would take about 5/6 hours and I have 200watts of solar. So to answer your question yes be concerned as your will kill your batteries boiling a kettle. I'm in Norfolk right now and on an average day might and I say might replace about 10/12 amps over the whole day.
     
  13. funflair

    funflair Funster Life Member

    Joined:
    Dec 11, 2013
    Messages:
    4,485
    Likes Received:
    4,741
    Location:
    Guisborough
    You only know what you have replaced when the sun goes down as the reading you are seeing with the sun on the solar panel is the voltage at the battery terminal so you are partly connected to the higher charging voltage from the regulator if you are fully charged it should be higher than 13 volts in the sun, I see the voltage going up to around 14.3 and then the amps being delivered cuts back relative to the amount of sun as the batteries cant take any more.

    I have to agree with John that kettles are not the best thing to be using on a small battery bank but that said your batteries seem to be performing OK if they held 12.2volts while you were hammering them.

    What batteries are you using @Dorset Diver

    Martin
     
    • Like Like x 1
  14. JeanLuc

    JeanLuc Funster

    Joined:
    Nov 17, 2008
    Messages:
    2,782
    Likes Received:
    1,859
    Location:
    Warwickshire
    Why on earth use 12v to power a 1000w kettle? Gas is the most efficient way to boil water.
     
    • Like Like x 3
  15. funflair

    funflair Funster Life Member

    Joined:
    Dec 11, 2013
    Messages:
    4,485
    Likes Received:
    4,741
    Location:
    Guisborough
    Well he did say he was new to using an inverter, possibly he just wanted to see what it would do.

    Martin
     
  16. Dorset Diver

    Dorset Diver Funster

    Joined:
    Dec 23, 2014
    Messages:
    368
    Likes Received:
    187
    Location:
    Somerset
    As you say I was only testing / trying the system out. In reality the only use the inverter will get is running the Nespresso machine (1260w for about 4 minutes) a couple of times in the morning and my wifes hair dryer (1400w) for about 15 mins twice a week. The batteries are 2 x 85 amp AGM's. I will always do my best to keep usage to a minimum.
     
    • Like Like x 1
  17. funflair

    funflair Funster Life Member

    Joined:
    Dec 11, 2013
    Messages:
    4,485
    Likes Received:
    4,741
    Location:
    Guisborough
    The Nespresso machine takes next to nothing out so that will be fine, 15 minutes continuous with the hair dryer will be too much in my view so you had better supervise the usage.

    Martin
     
    • Funny Funny x 1
  18. Dorset Diver

    Dorset Diver Funster

    Joined:
    Dec 23, 2014
    Messages:
    368
    Likes Received:
    187
    Location:
    Somerset
    Our off EHU usage tends to be 2-3 nights followed by a couple of nights on a site with EHU. Where possible hair drying will be whilst on EHU but ... well as you know SWMBO cannot have her schedule interrupted.
     
  19. JeanLuc

    JeanLuc Funster

    Joined:
    Nov 17, 2008
    Messages:
    2,782
    Likes Received:
    1,859
    Location:
    Warwickshire
    Apologies, I had not appreciated this was just an experiment.
    Some things have to have 230v and an inverter can be invaluable in these cases; my view is that wherever gas can be used instead, that is the best option when you don't have access to a mains hook up.
     
  20. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,475
    Likes Received:
    16,947
    Location:
    YO11 2BD
    Assuming it took 5 minutes to boil you will have used just 7amps.
    In good sun it will take maybe 2 hours to replace that 7 amps.
    The voltage you see after the kettle boiled will be solar output, not actual battery voltage.
     
    • Thanks Thanks x 1
Loading...

Share This Page