Can I run habitation aircon when travelling?

Discussion in 'Motorhome Chat' started by Cardeau, May 24, 2012.

  1. Cardeau

    Cardeau Funster

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    Hi all,

    I have no cab aircon but have habitation air con which is powered by an inverter? Can i use the aircon whilst on the move? Will it run down the leisure battery?

    Thanks in advance.

    Richard
     
  2. pappajohn

    pappajohn Funster Life Member

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    it certainly will if the inverter is off the hab batteries.

    the split charge relay will only replace a few amps to the leisure battery as it charges at the same rate as it charges the engine battery.
    if the engine battery is fully charged, which it should be with engine running, the alternator output will be very low so little charge to the hab battery.

    assuming the inverter only runs the aircon and nothing else then a second inverter, with a change over switch to isolate the hab inverter, connected to the engine battery would work well as long as the engine is running
     
  3. Addie

    Addie Trader - Motorhome Wifi

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    The Dometic air conditioning units can be made to work in motion with either a DC-2 or a DC-3 kit which, as I understand it, is little more than an inverter.
     
  4. hilldweller

    hilldweller Funster Life Member

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    There's one way to find out - try it.

    The fact that it is wired to an inverter hints that it will work.

    Does it say how many watts it consumes ?
     
  5. haganap

    haganap Funster Life Member

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    Mine would work for about 1/2 hour before it spanked th batteries. But as addis says It can be done with a alternator to battery charger or similar.

    But course someone will be along to say otherwise :Smile:
     
  6. pappajohn

    pappajohn Funster Life Member

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    of course it works Brian....thats how it works now, but the real question is....for how long before the hab battery is flat.
    obviously on hookup its not a real issue as the charger will keep the hab battery topped up, within reason, if used for short periods

    that was the reason for my suggestion of a second inverter running off the engine battery

    the Dometic aircon on my Kontiki was rated at 1700w start-up and around 1300w running
     
  7. pappajohn

    pappajohn Funster Life Member

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    I would agree Paul, around 1/2hr before the battery (assuming 110ah) would be 50% discharged.

    to be honest, mine was never used to keep cool, only to run up and keep things working.

    just the same with the twin units on the RV....never had cause to use either for cooling in the UK.

    if it gets a bit too warm, which it very rare here, i carry a 12" desk fan to move air around.
    moving air is cooler than stagnant air.
     
  8. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    Assuming its a Dometic/Waeco unit ad it has the proper inverter for it with a heavy duty split charge system and the vehicle has an alternator capable of putting out at least 100 amps then it shoul be ok to run whilst driving. If its an AC air con unit that has been connected to a bog standard inverter and no heavy duty split charge system or a smaller alternator then it will murder the leisure battery(ies) (assuming the inverter is connected to it/them) in short order.

    D.
     
  9. Gromett

    Gromett Funster

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    I am presuming when people use terms like kill and murder they mean the battery will die permanently not just use the all available juice in no time.

    It is important to note that the faster or deeper you discharge a battery the fewer charge/discharge cycles you will get.

    Unless as Dave and others have said.. You must have a proper system in place that will supply power directly from the alternator side otherwise you will be forking out for new leisure batteries in short order.
     
  10. SuperMike

    SuperMike Read Only Funster

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    Or as in the case of an RV, start up the generator and turn on the AC. :Rofl1:

    But then you probably don't understand, but if you did, I would have to kill you. :Eeek:
     
  11. slobadoberbob

    slobadoberbob Read Only Funster

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    as Mike says not an issue for the RV owners

    Like Mike if it is very hot in the back where Ezzie is.. I just fire the chassis generator up and put the roof ducted air on and cool the back down.. the cab has it's own Ford aircon system.

    I have a proper investor (pure sin wave by Sterling) 1500 watts.. but would not run my aircon off my batteries .. it would take them down to quick.. yes I use that via a EHU on site rather then run the genny. But no way would I just use the batteries.

    I doubt even with my 140 amp alternator I could throw enough charge back in to the the batteries while underway...


    Bob
     
  12. hilldweller

    hilldweller Funster Life Member

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    I thought it was normal for a relay to strap the two batteries together as soon as the alternator kicks in. So I did not understand that.

    However someone has just said 1500 watts, 100 amps, does the average alternator output this much ?

    That's 2 HP so it will increase fuel costs.
     
  13. hilldweller

    hilldweller Funster Life Member

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    I would argue that "within reason" and "for short periods" are not compatible. It either works properly ( as much as you want ) or it doesn't.

    Most chargers are not 100A.

    This is looking an abomination of an idea to me.

    Is there and Inverter/Mains switch lurking somewhere ?
     
  14. eddievanbitz

    eddievanbitz Trader - Funster

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    The DC Kit two and three link the engine and leisure batteries, connecting them through a voltage sensing relay (VSR) which is adjustable. The connecting wire used is (should) be a minimum of 25mmSq for short runs.

    The VSR will allow the inverter to use power from the leisure batteries and the engine/alternator simultaneously, whilst monitoring the state of charge of the engine battery. Should the engine battery fall below a pre set level the VSR will open the circuit and force the inverter to use the leisure battery only. This avoids arriving at your destination with a flat engine battery

    Even with the DC kits we advise careful use of inversion whilst travelling unless you know that when you arrive that you are going to have electric hook up so therefore not be relying on your leisure batteries.

    Hope this helps

    Eddie
     
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  15. dennismartin

    dennismartin Read Only Funster

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    i have 4 115 amp batteries and a 3kw inverter runs aircon for 2.5 hrs to 50% of batteries that was without engine running. i did run it for 4.5 hrs once batteries were pretty flat
     
  16. Gromett

    Gromett Funster

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    A couple of goes at doing that and you will have reduced your battery life considerably....:Sad:
     
  17. dennismartin

    dennismartin Read Only Funster

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    yeh i know wont be doing it again
     
  18. Cardeau

    Cardeau Funster

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    Thanks guys!

    Apologies for the late post, I've been too busy with work to look at the MHF website. Won't happen again I promise!!!!!

    Look's like I'll be opening the cab window unless I'm on EHU! I can always ask my wife to fan me with the atlas if it's too hot:Wink:

    Cheers

    Richard
     
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