Generator Woe and Reverse Polarity Light.

Discussion in 'Tech/Mech General' started by Another Lesley, Apr 30, 2014.

  1. Another Lesley

    Another Lesley Read Only Funster

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    Hi , it's me again with another possibly dumb question.:Sad: As I have previously said, techie is hard for me to understand, but I do try. Just come home from a couple of weeks away and had to use the generator to try top up the batteries as the solar panel was not sufficient.

    When I plug into the mains everything is tickety boo and everything charges as it should. Using the generator however has proved problematical. 1) It does not charge as quick....so perhaps my expectation is too great, but 2) The reverse polarity light comes on when using the generator, which I don't think it should. Now I have checked the book that came with the generator....and cannot see what, if anything I am doing wrong. I cannot see anything in the autotrail book either....but this I confess to finding confusing when it talks about anything 'leccie and I may be missing it. We have an 08 Autotrail Chieftain and have recently purchased a Hyundai HY3000 SEi. If anyone can throw some light (no pun intended) on this I would be grateful.:Smile:
     
  2. jhorsf

    jhorsf Read Only Funster

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    1 They all do that ignore the light when on the genny
    2 if you are charging on a genny with the 240 volt charger I do not understand the "it takes longer" makes no sense to me? its not possible?
     
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  3. Another Lesley

    Another Lesley Read Only Funster

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    Thanks for your reply, the generator does not seem to provide as much charge / speed in recharging as the 240. But I confess this may be my ignorance in what I am seeing....still trying to get my head around this particular blindspot:Sad:
     
  4. jhorsf

    jhorsf Read Only Funster

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    you mean with the same onboard charger?
     
  5. Another Lesley

    Another Lesley Read Only Funster

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    Yes, nothing else changes except the supply either mains or generator.
     
  6. TheDogMan

    TheDogMan Funster

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    I would have thought that the speed of charge is governed by the charger not the Genny, remember on mains its hours or days on Genny you are looking at a quick fix and the capacity of the charger may stop that
     
  7. TheDogMan

    TheDogMan Funster

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    1kw or 3 kw genny the level of charge will be the same
     
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  8. JeanLuc

    JeanLuc Funster

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    As others have said, if you are plugging into the 230V EHU point, the charging rate will be the same as if you were hooked-up to mains. (Note that this will charge quicker than if you plug a 12V output from the generator directly into the batteries - so don't try that.)
    Assuming you are not using masses of other 230V equipment in the van at the same time, the charger needs only a small generator to drive it. For most installations, a 1KVa (1 kilowatt) genny will be ample.
    I suggest it is all a matter of perception - when plugged into mains, you tend to forget how long the charging takes and the batteries never run down anyway once full. If, for example, you were trying to charge 2 x 100 Ah batteries from a low charge point, it will take over 24 hours - mains or genny.
     
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  9. tonyidle

    tonyidle Funster

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    If you use the "12v" output from the generator connected directly to the leisure battery (batteries) it will charge them much more quickly than the method you are using. The generator "12v" output is in fact a battery charging output, supplies 18v+, and is intended to boost charge a 12v battery. Only use it for an hour or so then revert to the arrangement you have been using.
     
  10. Tmesis

    Tmesis Read Only Funster

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    The output of the Hyundai's battery charging socket is only 8.3A compared to, in the case of my van, 20A. The battery charging voltage will not initially be 18v as this would demand more current than the trip will allow if the battery needs charging.
     
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  11. jonandshell

    jonandshell Funster

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    Fix this problem with-

    A bigger mains charger, or
    A Sterling Battery to Battery or Alternator to Battery charger, or
    Bigger solar panels.

    End of advice.:Smile:
     
  12. scotjimland

    scotjimland Funster Life Member

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    indeed.. especially for the unfortunate neighbour..

    an hour seems like eternity when a genny is running..
     
  13. tonyidle

    tonyidle Funster

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    See a previous reply. Because the van charger output is voltage-controlled and the battery has internal resistance it is unlikely that you would see more than (very approx.) 8A charge and then only very briefly.. Boost chargers work by offering a higher voltage to the battery than a normal charger and because of this can only be used for a relatively short time. You might be correct about the trip but my experience with a Suzuki generator rated similarly is that it will be OK - if it isn't then no harm is done.
     
  14. motorhomer

    motorhomer Read Only Funster

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    I don't understand some of the replies here. Surely charging rate has a dependency on the generator as well as the charger.

    A 1kw generator at 240 volts will provide just over 4 amps. A 3 KW generator 12 or 13. A mains hook up in the UK will typically provide 16 amps. Whilst I would not expect a charger to use a very high rate of current for long I doubt that it would be limited to 4 amps.

    So, surely a 1kw generator would be potentially a lot slower to charge than mains hook up??? This tome sounds normal and to be expected.

    But maybe I'm wrong and have remembered my physics knowledge wrongly!!!
     
  15. scotjimland

    scotjimland Funster Life Member

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    yes.. afraid you are wrong

    As you say a 1kw genny gives out ... 1kw, or 4amps at 230v

    a 230v van charger's output at a nominal 12v x 20A = 240 watt

    at 12v x 40A = 480 watt

    so well within the output of the 1kw genny

    max output from a 1000 watt genny = 12v x 83amps
     
    Last edited: May 1, 2014
  16. Terry

    Terry Funster

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    This may be a bit stupid but (just my impression from reading the thread) you are plugging your genny into the vans electric hook up point ? if you are then your van charger takes on the intended job :thumb: be it on hook up or genny so no difference in charging time :Smile:
    IF on the other hand you are using the 12v output on your genny with croc clips etc to your battery then this will depend on your genny's output which in most cases will be lower than the vans charger :Wink:
    Clear now?
    terry
     
  17. tonyidle

    tonyidle Funster

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    The van's "charger" is sized to supply the van services regardless of the state of the battery and to have enough in reserve to charge the battery as well. With a voltage-controlled charger the charging current is determined by the battery. A fully discharged battery (although it's not wise to fully discharge any battery) will accept a high current only for a brief period. As soon as the battery terminal voltage rises the current will fall dramatically. In the case of a leisure battery used until it is noticeably discharged rather than totally "flat" a maximum of around 8 amps is likely falling within an hour or less to maybe 4 or 5 amps.

    A generator with, as you say, a maximum 8A output will continue to supply around 8A for as long as it is connected. This is because the "12v" output of a generator is in fact much higher at around 18v. The rising battery voltage has much less effect. The generator output is not intended to supply 12v devices directly but to provide boost charging of a 12v battery. As such it should not be used for much more than an hour unless a VERY close watch is kept on battery voltage. If left too long there is a risk that the battery terminal voltage will rise above what can be achieved with a controlled charger. This could be damaging to any services in use in the van and ultimately to the battery itself. If a close watch is kept on the battery voltage the generator can be left connected until battery voltage starts to creep over 14.5v at which point the battery is as close to fully charged as the generator can safely manage.
     
    Last edited: May 1, 2014
  18. Terry

    Terry Funster

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    Hi Tony I don't doubt what you say (true or not) but I got the impression that the OP was confused by all the different ways the question got answered so I tried to simplify it :BigGrin:--I don't and never have had to plug a genny into my van but if I did I would not be watching a multi meter to make sure I did not goose the LB -I would simply plug it into the EHU point and let the charger do the monitoring for me :Wink:I think it's easier to simply plug and forget :BigGrin:
    terry
     
  19. Tmesis

    Tmesis Read Only Funster

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    I need to provide 100 amp hours to replace the 100 amp hours I have used. If I have only 8amps available, then in a perfect world I'd have to have the charger on for 12 hours to fully charge my battery. This is not negotiable.

    A higher voltage applied across the battery terminals will mean higher current as the voltage drop across the battery divided by the internal resistance of the battery will equal the current required. Assuming a constant resistance in the battery, the current draw is proportional to the voltage step-up of the charger.

    This current will be limited to 8 amps by the Hyundai as it uses a single winding for the 12V output. Multiple windings are used as input to its inverter to enable the much greater output of its 230V socket. So it's not just the circuit breaker that is limiting the charging abilities, it is a design limitation of the source of the 12v output.

    A commercially available boost charger will be rated at least 100A to achieve fast charging. A maximum 8A output will not compete with the built-in charger assuming that the built-in charger is a good one like the 20A elektroblock.

    Also, running at 18 volts will cause gassing as the gassing of a standard lead acid battery happens at around 15 volts.
     
  20. pappajohn

    pappajohn Funster Life Member

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    and the second part of your question....reverse polarity.

    The generator doesnt have a true earth which causes the rev polarity light to come on.

    Nothing to worry about and the polarity is correct...providing your hookup lead is correctly wired.
     
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