AC / DC Power Info Please

Discussion in 'Motorhome Chat' started by AdgeRas, Oct 13, 2009.

  1. AdgeRas

    AdgeRas Read Only Funster

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    LOL the thread title does relate to MH electrics and not the Rock Band :Laughing: (A long story for another time, but I did play drums for AC/DC at the Grey hound Croydon some 31 years back, albeit only one performance due to the real drummer being totally '**ssed' and unconcious).

    Any way, to stay on the right track: Being a newbie, please can some one explain a few facts for me.
    1: Being that there are what look like conventional 13 amp sockets in the MH, I assume I when I plug my lap top power lead, or my household toaster or any other conventional 240 volt item in, I am running off of the 'camp site' mains to power them.
    2: I know I can get what is called an 'inverter' so as to run 240 volt items off of the MH's batteries.

    Please can someone explain how quickly you would flatten your MH batteries powering 240 volt items, if you were not able to use option 1 and plug into the camp site mains electric?

    Do 'inverters' put a heavy strain on the abilities of the batteries?

    I am sorry if my questions are strange or not clear, my mind is as foggy as 'how to ask' as it is in 'finding the answer'

    Happy Travels

    Adge
     
  2. pappajohn

    pappajohn Funster Life Member

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    using an invertor.......

    if an appliance is rated at 230v and 100watts then using an invertor it will use 8.3amps per hour of battery power.

    use the 100watts as a reference point....ie...200watts = 16.6amps, 300watts = 24.9amps and so on.

    you should never flatten your battery below 60% capacity and recharge as soon as possible.

    using an appliance rated at 230v/100watt, a 75ah battery will be technically flat in 3.61 hours......a 110ah battery will last 5.3 hours.

    both batteries will run for much longer than the times above but may be severely damaged and need replacing.

    PS....got my sums right this time Olley and roger..:thumb:
     
  3. AdgeRas

    AdgeRas Read Only Funster

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    Thank you Pappajohn, but can you please explain the 'maths':

    If 100 watts would equate to about 8.3 amps per hour, and if you have a 75 ah battery, how does that only last 3.61 hours?


    Adge
     
  4. pappajohn

    pappajohn Funster Life Member

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    because you should never discharge the battery below 60% of its fully charged state

    so 60% of 75amps = 45amps

    ....ie 45amps remaining or 30 amps used.

    30amps divided by 8.3amps per hour = 3.61 hours

    50% is the absolute maximum discharge and may damage the cell plates.
     
    Last edited: Oct 13, 2009
  5. pappajohn

    pappajohn Funster Life Member

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    if you click this download it explains in more detail.

    page 3 gives you the voltages rather than calulating amps used.

    battery chart.
     
  6. Tony Lee

    Tony Lee Read Only Funster

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    Close enough - although it is normal to factor in an allowance for inverter inefficiency and other losses.
    If you allow 10 amps out of the battery for every 100W of 240V load that will give you a safety margin.

    If you are only ever going to power small items such as the laptop of a TV set, get only an inverter big enough for the maximum load you will connect at any time. Reason is that operating a 300W inverter at 80% load is more efficient than operating a 1500W inverter at 15% load.
     
  7. olley

    olley Funster

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    Well papa..........................not wishing to be pedantic but.......:Rofl1: your figures are only correct if you assume 100% inverter efficiency, which of course you won't get. :BigGrin:

    Like tony, I use a rule of thumb, 100watts at 230v means the inverter will be drawing 10amps out of the battery, 1000watts at 230v and its drawing 100amps, makes the maths so much easier for my poor brain.

    Olley
     
  8. hilldweller

    hilldweller Funster Life Member

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    But you are.

    You've not contributed anything significant to help OP.

    It's not just you it's loads of people across FUN/FACTS, got to have their say. Near enough is near enough.

    He was out by a factor of 10 in another message, I guess that was worth correcting and sure enough someone pounced.

    Jim has issued a Big Red Warning about belittling folk about their spelling, this nit picking is just the same.

    There, I've had my say, ruffled more feathers, never mind, I mean well.
     
  9. olley

    olley Funster

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    Hi Brian seeing as my post was a light hearted joke to papa, who I am pretty sure wouldn't take offence, why are you trying to lower the tone of the thread by your personal attack?

    Get out of the wrong side of the bed did we??

    Olley
     
  10. hilldweller

    hilldweller Funster Life Member

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    I made it clear it was not personal, an observation across FUN/FACTS I said. Technically I would say that nit picking lowers the tone by confusing the people who need simple advice not a debate whether it's 10 amps or 10.1 amps they have to worry about.

    Help people or confuse people, that is the question.
     
  11. olley

    olley Funster

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    Hi Brian I quote "You've not contributed anything significant to help OP." so that's not personal? And neither as it happens have your last two posts.

    This is not helping the OP, I suggest if you want to continue this, we do it with pm's.

    Olley

    PS. Hi Papa, just incase you are offended, please accept my apologies, I did mean the post in a light hearted way, which is why I put the smiley after "pedantic"
     
    Last edited: Oct 14, 2009
  12. hilldweller

    hilldweller Funster Life Member

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    There is nothing personal about this Olley, your ".not wishing to be pedantic but......" triggered my message as a general observation that technical posts often end up more as points scoring than significant content.

    I remember one "I've got a XXX", "I've got a BSc so I'm righter than you", thread. More testosterone than technical.

    I've made my point that "good enough" should do and would generally be best for people who need to ask the question in the first place. Simples :Smile:
     
  13. hilldweller

    hilldweller Funster Life Member

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    Well, after this lingering in the back of my mind for a while, it suddenly occurred to me that what I posted could well have come from one of the FACTS f&^&^%%&g moderators. That is not lowering the tone of this thread but the whole of FUN.

    I apologise to everyone. I will try and keep the grumpy old man within under better control. Promise !
     
  14. Brisey

    Brisey Funster Life Member

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    Brian

    If you think that I am going to Italy with one of the FACTS f&^&^%%&g moderators.
    you have another think coming.:Rofl1::Rofl1::Rofl1:
     
  15. hilldweller

    hilldweller Funster Life Member

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    Hey, that was supposed to be our secret, I thought National Coming Out Day was next week.
     
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