Inverter question

Discussion in 'Tech/Mech General' started by Mags52, Nov 10, 2015.

  1. Mags52

    Mags52 Funster

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    We have a 300w inverter bought from Maplins. It came with both a cigar plug connecter and wires to attach it directly to the battery. I want to use it to charge my macbook when we're off hookup - which currently in France is 90% of the time. I tried to use it in the cab cigar socket but it has fused the socket twice. I'm thinking that it might be more efficient if I wired it to one of the leisure batteries but having just replaced them at a cost of £300 I'm scared to try. Please advise.
    Thanks
    Mags
     
  2. funflair

    funflair Funster Life Member

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    I would go to the leisure batteries, much easier to start the van without a flat battery. You need to be able to isolate the inverter when it's not in use though.

    Martin
     
  3. Mags52

    Mags52 Funster

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    Our inverter has an on/off switch. Will that do to isolate it?
     
  4. funflair

    funflair Funster Life Member

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    Should be OK.
     
  5. Dave and Ginny

    Dave and Ginny Funster

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    I asked that same question on another thread and got the answer 'yes'. You need to incorporate a fuse in the wiring from the battery though, and for a 300w inverter it needs to be 25/30 amp.
     
  6. Welsh girl

    Welsh girl Funster Life Member

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    We use our 300 watt pure sine wave inverter with the cigar plug but usually only do my toothbrush and the 50 watt freesat box, have never blown it.
    Wonder why it blows on yours.
     
  7. scotjimland

    scotjimland Funster Life Member

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    Mags.. is it a pure sine wave model ?

    If not PSW, it won't run the Mac.. if it is then how will you connect to the leisure battery ? croc clips or permanent connection ?

    Using the switch on the inverter is ok, but better if installed properly with a relay and toggle on/off switch..

    JeanLuc has uploaded an excellent guide to fitting a small inverter properly, download here .. .. http://www.motorhomefun.co.uk/forum/resources/install-a-small-inverter.17/



    that is how I have installed mine, using a 200w Sterling PSW ..which I use primarily to charge the Macs. I also fused the Line feeding the Switch and used a 20A Auto relay. The twin 13A socket is optional...

    drawing courtesy of @JeanLuc

    upload_2015-11-10_7-40-41.png
     
    Last edited: Nov 10, 2015
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  8. Dave and Ginny

    Dave and Ginny Funster

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    Wished I'd seen this when I wired mine up...it's been fine but would have preferred an isolating switch close to battery.
     
  9. Clarky

    Clarky Funster

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    I have a cheapo Maplin 300w inverter that I bought years ago to run a mains tv in a caravan. It sounds the same as the OP's.
    I still carry it in the garage and use it to charge my Mac book and my shaver with no problems.
    Haven't used it from the dash sockets but from 12v sockets in the hab area and the garage. No fuses blown so far and the Mac charges OK.

    Richard.
     
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  10. mitzimad

    mitzimad Funster

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    we to have powered a laptop charger from a little inverter but i always cliped it on to the battery lighter sockets are a pain to use i would hard wire it to the leisure batteries with just an inline fuse the switch on the unit will do to turn it of if its accesable and the wiring is fixed
     
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  11. Jaws

    Jaws Funster Life Member

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    Fag lighter sockets SHOULD be fused at a maximum of 10 amps..
    That is what they are usually rated at.. I have seen a few in my time that have completely melted !!
     
  12. Don Quixote

    Don Quixote Funster

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    Mags I bought one of these for my macbook and works a treat:
    mac2.jpg
    I leave it connected whilst driving as well so macbook is fully charged on arrival and I can charge my iPhone at the same time. Bought from amazon, but cannot do a link on here. Called
    DC 12V Car Charger for Apple MacBook Pro 13-inch models 60 Watts Magsafe (ORIGINAL ELECTRONIC EQUIPMENT ®)
     
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  13. scotjimland

    scotjimland Funster Life Member

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    Two models on Amazon..


    and if you have the Retina display



    I looked at buying one of these but as it is not an Apple product, in the unlikely event it did any damage it would invalidate the Apple warranty .

    To my Knowledge Apple do not make a 12v adapter, nor have they licensed the Mag Safe connector to a third party ..

    EDIT .. you will need to search
    very strange the url LINKS are not working @Jim

    when inserted as URL links they have [Media] brackets
     
    Last edited: Nov 13, 2015
  14. Mags52

    Mags52 Funster

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    Great idea - will get one when we're back in the UK. This long trip has taught me a lot about conserving energy. Thanks
     
  15. Reallyretired

    Reallyretired Funster

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    It's always more efficient to use a 12v charger with this sort of thing rather than an inverter. I charge everything from 12v adaptors except my video camera and the toothbrushes which have no 12v charger available. For these I have a 300w pure sine inverter which was cheap.
    Running an inverter from a lighter socket is not likely to be successful except the little 75w one. A 300w inverter can draw 30A and the lighter socket will only be rated at 10A.
     
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  16. pappajohn

    pappajohn Funster Life Member

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    Im really surprised this was supplied with a fag lighter plug.

    At full potential (300w) it will draw 25amps....even an auxilary fag lighter type socket is only rated at 15amps.
    300w÷12v=25a

    Throw away the lighter plug and clip to your battery...better still, hardwire it in.
     
  17. Big Nick

    Big Nick Funster

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    You can get 12v car chargers for most gadgets which is a far easier solution
    I've just got one for my Lumix camera for £12....works a treat!
     
  18. DABurleigh

    DABurleigh Funster

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  19. MyDogsTooBig

    MyDogsTooBig

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    It's a long one. Sorry. Apple Macs require more than 12 volts to charge them, that is why you do not see 12v chargers for them and why you can't just plug one into a 12 volt USB charger (despite the proprietary plug). The charger shown above will convert your 12v to a higher voltage for charging. I would not use one, purely because I do not trust this Chinese stuff not to screw up and a MacBook is a lot of money to screw. With your inverter, a bit of simple maths will help you out. If you plug any 12v inverter into a battery supply, regardless how you do that, with nothing plugged into the inverter, it will immediately charge its internal capacitor bank. This will be a very very short high current pulse. Less than 1/4 second. This pulse is a magnitude of amps and is proportional to the size of your inverter. The inverter will normally recommend a suitable fuse. If the fuse you use is of too low a rating, just plugging in the inverter, with nothing attached, will blow the fuse. The inverter will draw a standby current when plugged in, even if nothing is connected to its output socket. Depending again on the power rating of the inverter, this will be anything from say 1/4 amp, up to 8 amps for large fixed units of poor quality. Your inverter is rated at 300 watts, which will probably be peak i.e. maximum for a defined duration and probably only 150w or so for continuous use. However, just divide the inverter wattage (300) by the voltage (12) and you get 25. That's 25 amps roughly maximum the inverter is going to draw from your battery. The inverter will only draw that sort of current, if you connect a 300w load to it. So, if you just say plug in a 60w household lightbulb, then the inverter will only consume 60 divided by 230 (that's the EU harmonised voltage for UK and Europe), which is 0.26 amps, lets round that down to 1/4 of an amp for simplicity. The inverter works at 12 volts, so divide 12 by 1/4 and you get 3. Your inverter will be drawing 3 amps for your household light bulb, plus any standby current it requires (as mentioned perviously) to operate its electronic bits. Lets call it 4 amps altogether. Now there are 2 types of 12v receptacles. Cigar/cigarette and utility. They are not the same. The former is designed to physically hold a lighter and heat it up, so its base is ceramic (where the centre connection is). Utility sockets are not designed to light fires, so their base is just plastic. They are actually physically different. The cigar lighter is not designed to supply lots of current. The wires to it are really very thin and the fuse rating is normally only 10 to 15 amps maximum. A utility socket is very much the opposite. So, yes plug your inverter into your utility socket, but work out how much power you will be drawing from it. The household lightbulb, as you can see is no problem at all, but even 15 amps is really too much. As the other poster said, don't use your cab battery, that's a disaster in the waiting. With reference to the diagram above; The main fuse should be rated according o your inverter, so the show 40A probably will not be appropriate for you. The fuse should be as close to the battery as possible. The battery supply to the switch, should be fused with a 1 amp fuse. The reason is that if somehow the large power cable of the switch cable connected to the battery, gets rubbed or trapped to the bodywork, then having no fuse will just cause a fire and having a fuse after where the wire gets trapped is pretty pointless. It just isn't going to blow. Its is not just about the inverter shorting out. The diagram shows a twin socket remote from the inverter. This is a concern. Plug one item into the inverter, fine. By extending the cable to a twin socket implies more than one appliance can be connected at the same time. An inverter is no different to a generator and no different to the national grid. The inverter output should not only be suitably fused, but also protected by an RCD (Residual Current Device), which will save your life if a fault develops in a mains appliance. However, one will not work in this situation, because the output of the inverter will be 'floating'. It is all very complicated, but basically, small inverters have a socket on them. Use that and nothing else. Multiple sockets need to be wired through a fixed installation with neutral connected to chassis and an RCD employed. Not always possible with all inverters either. Stay safe eh.
     
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  20. hilldweller

    hilldweller Funster Life Member

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    Surely not. I'll bet you fitted a small fuse to protect the thin wiring to the relay coil.
     
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