Electrics basics...?

Discussion in 'Motorhome Chat' started by Encantador, Feb 27, 2012.

  1. Encantador

    Encantador Funster

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    trying to understand more about how Mh electrics work.

    I have two leisure batteries but not sure what size, also have one solar panel but cannot find anything that telles me whether it is working or not.

    I have a few 3 pin domestic type sockets and a couple of 12v cigarette lighter type sockets for TV. The TV in bedroom has one of each. I purchased a cigarette lighter lead with TV so use that, have not tried any of the 3 pin sockets.

    Am i right in thinking that I can only use the 3 pin sockets when on EHU, if that is correct, what difference does it make when a site description says something like "EHU 16A", and how does this number affect what you can and cannot do? I gather that abroad it can be a lot lower, is that correct?

    I also read about people having various sized inverters on board, are these an essential piece of kit? What does having one mean you can do that you can`t do without?

    Thanks

    Steve
     
  2. pappajohn

    pappajohn Funster Life Member

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    solar panel is generally fit and forget.....ideally you need a voltage tester to rerally see if its working as it should.

    3 pin sockets only work on mains hookup or generator.

    16 is the number of amps the supply can provide withput tripping the hookup post.

    16amp is the commonest in the UK but can be as low as 5amps on European campsites.

    16amp will allow up to 3680 watts of power.

    to decide how many watts an appliance uses you need to find the data label of the appliance...sometimes its stamped/embossed on the appliance base.

    an average domestic kettle could be as much as 3000watts (13amps)
     
  3. pappajohn

    pappajohn Funster Life Member

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    forgot to mention the inverters.....

    an inverter will produce 230v AC (mains) from 12v DC (battery) but the battery drain can be high.

    an inverter will run smaller appliances, 60watt tv etc, without much trouble but if you have a big inverter it can get power hungry.

    a 600watt inverter running a 600watt appliance will use around 50amps of battery power per hour, the same appliance running on mains hookup will use around 2.6amps per hour, so really you need plenty of battery power and a fast means to charge the batteries.....
     
  4. tonka

    tonka Funster Life Member

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    Ref mains.
    13amp plug sockets in the van, yes only when on EHU.. and before anyone shouts "inverter" lets leave it at that so you dont get confused yet,,
    Almost all mains electrical items will have a label stating their wattage, as a simple rule of thumb 1,000 watts = 5 amps.... So if you had a 16amp supply you could run just over 3,000 watts (3kw. kilowatts). Some campsites will limit the supply right down to say 6amp = 1200watts.. This is so you dont plug in large heaters etc and use loads of energy..
    It's always wise to buy low wattage appliances to avoid tripping the system. Eg travel kettle at 1200 watts rather than a domestic 2/3kw rapid boil.. This way if you do get a low amp supply you can still cope.. Remember anything that heats takes lots more power.

    12V Leisure battery,,
    Look at your batteries and there will be an amp rating ie 85 or 110 etc..
    Whatever it is work on having only 50% of it available..
    Similar principal applies, for every 12 watts of power that is 1 amp of drain from your battery. So a 12v TV at 48 watts = 48 / 12 = 4 amps.. Tv on for 4 hours = 4amps x 4 hours = 16 amps from your battery..

    Solar..
    This will replenish the amps in your battery,, eg 80w panel may generate 5amps, but this is a max depending on lots of factors,, But say its middle summer and it is giving 5 amps for 10 hours... 5 x 10 = 50amps....

    Does this help any ?? dont want to make it to long winded..
     
  5. Encantador

    Encantador Funster

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    Thanks, so for charging a laptop/mobile for instance, this can only be done when on EHU or by using an invertor when the engine is running (to avoid too much drain on the batteries)?

    Steve
     
  6. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Ok-I'm no techy-so,here's how I understand it: watts=volts x amps. so,if I've got 16amp supply at 240 volts I can run 3680 watts. Our domestic kettle at home is 3000 watts :BigGrin: so you aint got much !!.Kettle and iron and you blow the trip for sure.
    In Portugal Carolyn switched a very low power hair dryer on and 'Poof' the trip went-we were on a 6amp site :BigGrin:.

    An invertor converts your 12v supply to 240v-but it does use a fair bit of power to do this.
    with 2 x110 ah batteries we can run a laptop for about 1 hr before dropping below 80% battery charge.
    We use our invertor mainly for charging stuff whilst we are driving.
    sounds like you need some sort of battery monitor to tell you whats going on.The NASA BM-1 is a good piece of kit (google it)
    No doubt someone who really knows whats what will be along soon-hope that helps.

    Mike.


    oops-they came along whilst I was typing that lol.
     
  7. Reallyretired

    Reallyretired Funster

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    The really low rated EHU you sometimes get abroad can sometimes be as low as 4amp (just under 1kW) and so you can run your fridge and battery charger and thats about all. Everything else needs to be gas. It is best to get a low wattage kettle, Tesco do one that is 1Kw, otherwise you need to turn every thing else off to boil a kettle. Some UK sites are only 10A so a 3Kw kettle is out, but it will run a fan heater on low setting.
    Other high wattage items that are used in motorhomes are;

    Hairdryer 600-1200 watts (roughly 3-6Amps)
    Toaster (2 slice) 600-800 watts (3-4Amps)
    Microwave 1200-2000w (6-10A)

    Things like TV, computer etc are lower wattage.
     
  8. Encantador

    Encantador Funster

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    Have I read somewhere that any kettle that is usable is way too slow so it`s best just to use gas?

    Steve
     
  9. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Because we spend a lot of time without EHU we do not have either an electric kettle or toaster.We use an ordianry kettle on gas and a 'Yellowstone' toaster on gas hob (frankly it produces much better toast than an electric-just remember to put smoke alarm under duvet first :BigGrin:
    Mike.
     
  10. tonka

    tonka Funster Life Member

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    NOTE.. Microwaves are a bit of a funny one.. although it may say 700w on the front, thats the output power.. Check the label on the appliance as usually they are almost double that as Really retired has listed..
     
  11. Reallyretired

    Reallyretired Funster

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    No I wouldn't say that. I reckon our 1Kw Morphy Richards kettle boils in a reasonable time, obviously not as fast as a 3Kw kettle, but as it's smaller it holds less water (Enough for 2-3mugs) and so the difference is not so great.
     
  12. pappajohn

    pappajohn Funster Life Member

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    gets confusing now......

    many electronic appliances, lappy etc, dont like invertors unless they are the more (lot more) expensive pure sinewave invertors.
    pure sinewave is the same as plugging into the mains at home....cheaper modifies sinewave inverters are made to act like the mains but have very different and damaging characteristics

    so, a cheap inverter can damage your laptop...among other things.

    if an appliance is supposed to heat up.....curling tongs, kettle, toaster etc a cheaper inverter will do it...if it has a motor or sensitive electronics, it may not do it.
     
  13. Reallyretired

    Reallyretired Funster

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    It is also very inefficient to run a low voltage appliance like a laptop from an inverter. Get yourself a 12v power supply for the laptop and you can use it all day from your batteries.
     
  14. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Elucidate lol-sounds like we need one o' they-where from ??
    Mike.
     
  15. pappajohn

    pappajohn Funster Life Member

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    I have a 700watt kettle which takes slightly longer to boil than it does to make the drink ready for water.....milk out, add to mug and back in fridge, sugar and coffee out, ad to mug and in cupboard.
    couple more mins and the kettles boiling.

    whistling billy kettle on the gas hob takes longer to boil.
     
  16. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    I know -but so relaxing :Rofl1:
    Mike.
     
  17. pappajohn

    pappajohn Funster Life Member

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    yep...feet up just waiting for that first little 'whine' from the whistle and thinking how easy it would be to open a beer instead:Laughing:
     
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  18. Reallyretired

    Reallyretired Funster

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  19. Encantador

    Encantador Funster

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    Thanks for the replies, think I am getting there slowly (very slowly).

    When looking at the state of the leisure batteries on the control panel when not on EHU, what numbers should i be looking for before doing something and what should I be doing, running the engine i assume.
     
  20. pappajohn

    pappajohn Funster Life Member

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    panel volt meters are notoriously inaccurate and cant always be relied on.

    if its sunny and the solar panel is working you should see around 13.6v or maybe more and don't really need to do anything.

    night time, or panel not working, if the meter shows below 12v and nothing is plugged in to 12v then its time to recharge.

    if you have TV etc plugged in, the meter will show a bit lower than the true voltage due to the load on the battery so you could go as low as 11.5v

    the engine will put some charge in but not enough to charge fully and could take a few hours of running.
     
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