Starting Engine Whilst On Ehu

Discussion in 'Motorhome Chat' started by laneside, Jun 13, 2015.

  1. laneside

    laneside Funster

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    This maybe another scare mongering urban myth or something specific to Rapido but I have just been reading the handbook and it states in big capitals a warning DO NOT START THE ENGINE WHEN ON MAINS HOOK UP. I never knew this and I bet many more do not but I am sure someone will be along soon to educate us
     
  2. Techno

    Techno Funster Life Member

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    In case you drive away with the hook up post :LOL:
     
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  3. DavidG58

    DavidG58 Funster

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    My Hymer warns / reminds me if I am still connected, but I presumed this was to remove the risk of ripping the post out of the ground or the socket out of the MH

    That said I have on a few occasions still been warned I am connected when I have definitely disconnected, I don't know if it is faulty or a function of the solar panel output

    I do not have a substantiated technical answer but really cant see what harm could be done (y)
     
  4. Mel

    Mel Funster

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    The only problem I had when I did that was sparks from the cable when it left the plug in the Motorhome. Oops.

    Mel
     
  5. Techno

    Techno Funster Life Member

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    If a manual is going to make bold statements like that it should at least explain why even if the end user would not understand.
    In fact if it is so critical there should be a means to prevent it happening (not everyone has or reads a manual)
    Yesterday after pitching up I decided the van could go back another couple of feet, it didn't catch fire
     
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  6. TheBig1

    TheBig1 Funster Life Member

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    some battery chargers dislike a higher voltage fed back into them from the alternator
     
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  7. old-mo

    old-mo Funster Extra Special Life Member

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    I get a loud buzzer going off...

    But as soon as I disconnect it stop`s... :)
     
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  8. K9Brian

    K9Brian Funster

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    Typical male - 3 years on and just getting round to reading the handbook :whistle:
     
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  9. laird of Dunstan

    laird of Dunstan Funster Life Member

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    It's probably due to the risk of two conflicting power supply and related to the earthing causing problems related to electrical/ electronic components opposing each other.
    I may be wrong :whistle:
     
  10. jonandshell

    jonandshell Funster

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    Our van is left permanently on hookup at home.
    I have a coiled lead (like a telephone handset lead) to avoid snagging.
    I am shunting it back and forth quite often to gain access to our garage up and over door.
    No problems to report!
     
  11. SandT

    SandT Funster

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    Technically its because if you are on EHU and the engine is running the electric 220/240 volts might meet the 12v
    supply . Now this is the important bit ......

    If they don't get on they might have a fight and the big electric will hit the little electric right in the googlies causing the little electric to run away and cry and you don't ever want water in your electrics!

    Hope this helps. :rolleyes:

    Terry
     
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  12. GJH

    GJH Funster Life Member

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    I've read this in the past and that it is for reasons such as these. I think it differs between vans, though, depending on components used and how they are interconnected.
     
  13. jonandshell

    jonandshell Funster

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    Look, lets look at this carefully and not perpetuate more internet myths, or in layman's terms, bollocks!

    Built in charger is switched on. It applies voltage to your batteries.
    You start your engine, the alternator applies voltage to your batteries.
    Now, one of these, probably the alternator, will supply more voltage than the other. The provider of the lower voltage will cease to provide charge.
    There is no conflict, sparks will not fly. 240v AC will NOT come into contact with your 12 volt system!

    How many of you worry about disconnecting your solar before you start your van or connect the EHU lead?
     
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  14. Gromett

    Gromett Funster

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    In General I would agree with jonandshell. However...
    I have burnt out a charger by starting the engine with the EHU connected.
    The charger was an el Cheapo, I had flat batteries and had connected the EHU to recharge the van battery. I gave it 20 minutes then started the van. It took some starting. I got a nasty smell from the back of the van and when I looked the Charger was smoking.

    It appears the El cheapo charger had no thermal protection and for some reason the voltage regulation was confused by the nature of the load and gave it everything it had resulting in a burnt out transformer in the charger. Needless to say I have never bought an El Cheapo charger again.
     
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  15. scotjimland

    scotjimland Funster Life Member

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    spoilsport.. we love myths and bollox on Fun .. it's the lifeblood.. :cool:

    where would we be without a good gassing tale, or 20 car pile up on the M25 caused by a vanner dumping slippy grey water :LOL:
     
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  16. peterc10

    peterc10 Funster

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    Haven't had one of those for a couple of weeks. Probably due one soon.
     
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  17. Don Quixote

    Don Quixote Funster

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    Alan, "DO NOT START THE ENGINE WHEN ON MAINS HOOK UP" because ???? - I would say CRAP manual and would be emailing Rapido asking WHY this is stated and WHY the reason was left out. By the way...... you are the first man I have come across who reads the manual all be it 1/2/3 years late.....
     
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  18. John Laidler

    John Laidler Funster

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    My guess would be when you start the engine the starter battery voltage drops significantly for a short time as it starts cranking the engine. At this point the MH charger may produce too much current as it tries to maintain the engine battery voltage.

    This doesn't mean the MH system will burn out every time, it may have overload protection and if the engine battery is in good condition the drop in voltage may not be severe - but it could happen.
     
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  19. Judge Mental

    Judge Mental Funster Deceased RIP

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    Please dont! You may well set of a cataclysmic chain of events that may hasten the end of the world!
     
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  20. GWAYGWAY

    GWAYGWAY Funster

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    I thought about fitting a nitrous oxide power upping kit and fitting it in the living area instead as it would liven up the solemn atmosphere
    I could then sell them to MH's and when they all passed out I could rob them for insurance purposes.
    WILL THAT START IT OFF ????
     
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