Running engine while on hook-up?

Discussion in 'Motorhome Chat' started by maz, Oct 24, 2012.

  1. maz

    maz Funster

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    A few days ago there was a guy sitting in a rented motorhome with the engine running for about half-an-hour while still plugged into the mains. It was kind of early in the morning and when I got back from walking the dog he had left so my curiosity about this was never answered. :Blush: All I can think is that he was using the demister to clear the windscreen of condensation before driving off.

    I thought running the engine while on hook-up was a no-no. It's something I've never done but realise that I don't actually know why. Is there a risk of frying the batteries if you do this?
     
  2. jonandshell

    jonandshell Funster

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    The mains charger reads the leisure battery as being charged, due to the fact it is having voltage applied by the alternator, the mains charger simply stops charging!

    This is only true for a 'smart' four-step mains charger, however!

    An old-style fixed-output charger will simply keep going, adding to the alternator's efforts!
    However, because a battery's internal resistance increases with it's state of charge, it will only 'soak up' what it needs and current flow will all but cease when a full state of charge is achieved. As long as the output of the charger, and the alternator are correctly regulated.

    So, as long as everything is in good working order, the battery will not be harmed!
     
  3. peter marshall

    peter marshall

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    Hi
    I answered a post on here a while back, he had lent the MH to his son for the weekend and he blew the leisure battery fuse due to running whilst plugged in. Pete
     
  4. robinwickens

    robinwickens Read Only Funster

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    As an engineer I would say that if all circuits were sufficiently protected then there SHOULD be no problem with charging a battery from several different sources.
    A battery will only charge to a certain capacity and each charging circuit should record this and shut down.
    This should be true of 240v, 12v, generator or solar charging.
    Even if all were providing charging current they should all recognise a fully charged battery.
    The only problem that might occur is that the battery might not be able to accept the total amperage that is injected but this would be governed by the most powerful charger in circuit which normally would be the 240v circuit.
    I think that this should not concern most of us!
    Would you consider for instance not using your gas ability when heating your hot water? I for one always use gas as well as the 240v heater when first setting up on site if 240v is available and then switch over to 240v only when boiler is up to temperature.
     
  5. Jaws

    Jaws Funster Life Member

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    This is a bit like the 'how long is a bit of string' question

    Both my van and my sons Compass suffers no ill effects if running the engine on hook up, but as said, there are lesser systems that will pop fuses or worse

    To be on the safe side I would suggest not doing it.................

    As to why matey was doing it.. no idea apart from perhaps his leisure battery(s) or charger was buggered, he was using the van battery to keep 12v stuff working and the hookup for 'things mains'
     
  6. deanroofing

    deanroofing Funster

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    Having read this thread, seems that it's ok to stay on hook up over winter, are there any downsides to this, last year my leisure battery got knackered,don't know why, but did have it on hook up for quite awhile, thanks in advance to answers.
     
  7. scotjimland

    scotjimland Funster Life Member

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    Biggest danger is forgetting to unplug and driving off ... only done that once.:Doh:

    This was on a French Aire, in my haste to get an early start forgot about it .. .. not to be advised.. felt a right fool.. :Laughing:
     
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  8. maz

    maz Funster

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    Yes I do that too but the heater has settings for using both gas and electric together.
     
  9. ehuplad

    ehuplad Read Only Funster

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    The worst thing you can do to a engine is leave it ticking over for long periods. :Eeek:

    We once did a test to a engine 1000hrs on tickover, not a very nice site when it was stripped down. this was also before all the new emissions gadgets were around, the tickover does not do them much good either.
     
  10. Jaws

    Jaws Funster Life Member

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    A lot of us have solar panels so effectively the batteries are being charged all the time.. No issues at all :thumb:
     
  11. eddievanbitz

    eddievanbitz Trader - Funster

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    I regularly have the engine running to get it up to temperature before pulling straight out, towing a car into traffic going 60 MPH when staying on motorway Aires, add to this I have a 100Ah charger and have the genny on for the AC etc and two 130W solar panels.

    I cannot see why the batteries should react to any of this any differently than sitting on hook up with the output of the panels.

    The alternator will not do anything if it senses there is no need, neither will the charger or the solar regulator.

    As for older systems, they tended to be very low out put any way so again, wouldn't really effect anything.

    Now dynamo's lol! That is a different matter lol

    Eddie
     
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