What size inverter.

Discussion in 'Motorhome Chat' started by plumbomb, Dec 11, 2014.

  1. plumbomb

    plumbomb Funster

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    HI, were looking at having a Pure Sine inverter fitted to our 2013 AT Apache634. We had a 85w solar panel fitted as a extra by AT & we have one leisure battery. the question is what size inverter,it will only be used for charging iphones,ipad & sometimes the wifes hairdryer.
     
  2. hilldweller

    hilldweller Funster Life Member

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    And that is where it all gets messy. Huge great inverter, huge great cables like tow ropes. Battery flat in no time.

    Whereas the phones etc only need a neat little inverter that will plug into a cigarre socket.
     
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  3. Gizmouk

    Gizmouk Funster

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    For phone / iPad charging we use one of these:
    http://www.amazon.co.uk/gp/product/B00GYNW1TA

    Hairdryer - forget it. Calcs based on the bottom end of the range, 1KVA @ 12V
    Cable size 16mm2 (calced on 3m run in free air)
    Autonomy using 85Ah battery to 50% discharge - about 3 minutes.

    Best advice - buy her a towel for Christmas :roflmto:
     
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  4. scotjimland

    scotjimland Funster Life Member

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    as they say.. ^^^^ (y)
     
  5. bungy

    bungy Funster

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    or just wire the inverter to the cab battery for the hair dryer use and have the engine running whilst its in use - and run the drier on low setting!! wife uses a 1200w one on the low setting and a 800w inverter copes nicely
     
  6. Jaws

    Jaws Funster Life Member

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    We have little 12v chargers for everything we use, from the fones to the kindles to the laptops to the iPads
    Absolutely no need for a battery killer at all :)

    And yes, get a bigger towel for hair LOL !!!
    just to give you an idea
    we have 300 watts of solar panels, 280aH of leisure battery and the only inverter I have is a wee little 300w jobby that to be honest I have NO idea what we would ever use it for except perhaps if we were off grid for a week plus and needed to recharge the eclectic cycle batteries
     
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  7. JeanLuc

    JeanLuc Funster

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    If you cannot get suitable 12V charging adapters (e.g. Apple proprietary connectors) then a small 150W PSW inverter will be adequate. As others have said, a hairdryer is a completely different 'kettle of electric eels' - you cannot optimise both hair drying and small appliance charging.
    Here is my solution for low power needs:
    http://www.motorhomefun.co.uk/forum/resources/install-a-small-inverter.17/
     
  8. davejen

    davejen Funster

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    Open a window and tell her to stick 'er 'ead out!
    Cheers, Dave(n):xlaugh:
     
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  9. jemhorn

    jemhorn Funster

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  10. funflair

    funflair Funster Life Member

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    How is the maths working here 1KVA is close enough to 1ooo watts, so with a few losses is about 100 amps for 3 minutes is 1/20 hour which I work out at 5ah, which a solar panel would put back in 2hrs sun willing of course.

    Or am I wrong, would not be the first time.


    After saying all that, two batteries would be better I run 2Kw inverter 0f 160 ah and use Microwave, Coffee machine and wife uses hair dryer and panels will put it all back in a couple of hours.
     
  11. Techno

    Techno Funster Life Member

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    I just love the opportunity :xlaugh:
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  12. pappajohn

    pappajohn Funster Life Member

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    since when did it only take 3 minutes for a woman to dry her hair ? :xeek:
     
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  13. funflair

    funflair Funster Life Member

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    Just took somebody else's numbers, nowt to do with me Guvnor.
     
  14. hilldweller

    hilldweller Funster Life Member

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    Yes, when it comes to BIG amps. That 100Ah battery will be specified at 10 hour rate, so 10 amps for 10 hours ( except we normally only discharge to 50% so 5 hours )

    But and this is a BIG BUT, go to 100A discharge and the numbers change dramatically. The chemicals cannot react fast enough and the battery becomes 25Ah.

    Rough figures and depends on battery construction with traction batteries dramatically better because they are designed to drive high loads and will have more lead plate area.

    You want heat, use gas. When the day comes and electric vehicles are viable then we can have a re-think.
     
  15. hilldweller

    hilldweller Funster Life Member

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    When she dries her pubic hair.
     
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  16. Reallyretired

    Reallyretired Funster

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    I must beg to differ. We have 2x125Ah batteries and 400w of solar with a 1500W (3000wPeak) inverter and run hairdryer 1200w , microwave 1200w and kettle 1000w without hookup in the summer. No probs. The inverter is close to the batteries with massive cables supplied with the inverter. Having 2 batteries effectively halves the current from each battery ie 1000w will draw about 50A from each battery. Fuses are 300a to the inverter and 150a between the batteries.
     
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  17. funflair

    funflair Funster Life Member

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    Even 50% is still around 50ah which in theory is 100amps @12 volts or 1Kw from 240 volt inverter for 30 minutes to flat not 3 minutes. Not that I would recommend that regime but happy to pull 100-150 amps off our old Gells for 5 minutes.
     
  18. hilldweller

    hilldweller Funster Life Member

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    Can't argue with any of that.

    For the benefit of others, how long can you run the microwave ?
     
  19. Techno

    Techno Funster Life Member

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    If you want a home from home you can't be unrealistic, you must man up or make do!
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  20. sallylillian

    sallylillian Funster Life Member

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    A key issue is type of battery if you are talking about these levels of amps being pulled. With big AC amp levels you really need AGM's which are comfortable with large amp draws and have acceptance levels of 2-3 times the total amps of the battery. The next is that whilst taking your bank down to 50% SOC before recharging is perfectly practical you are dramatically reducing the life of the bank compared to say 75%. If you are using your batteries in this way it is important to get a full charge, and that means getting to float for circa 12 hours or so on a regular basis.
     
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