12v wiring advice

Discussion in 'Motorhome Chat' started by PJGWiltshire, May 19, 2017.

  1. PJGWiltshire

    PJGWiltshire Funster

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    I am looking to install a double USB charging socket. The most convenient position is immediately next to the TV station, which in my van is a pop up type from behind a fixed seat. The TV is wired directly into the 12v wiring system and fused as part of the 'Media ' circuit in the main fuse box. The fuse on the Media circuit is 20A.
    Having read up on the USB socket ( a double which supplies a 1A and 2.1A outlet) mention has been made that it should be installed with a 10a fuse.

    This is where I get confused. My thoughts are simply to splice into the TVs + and - wires and then let the 20A fuse protect the USB charger as it will now be on the media 12v circuit. Will there be issues around the fuse size? My intention is for the USB charger to charge iPhone on the 1A side and the iPad on the 2.1A side.

    Hope someone can help
     
  2. scotjimland

    scotjimland Funster Life Member

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    Fuses are fitted to protect the cable from overload.. so the 20A fuse is fine.

    When you splice in, fit an in-line 5amp fuse to protect the new circuit.
     
    Last edited: May 19, 2017
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  3. PJGWiltshire

    PJGWiltshire Funster

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    Many thanks,
     
  4. pappajohn

    pappajohn Funster Life Member

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    Wot Jim said....but 10a sounds a bit high for a USB socket drawing a max of 3.1 amps.
    I think i would start with a 5amp, if that blows then a 7.5amp, if that blows theres something wrong.
     
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  5. PJGWiltshire

    PJGWiltshire Funster

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    Will do thanks
     
  6. Sheddy

    Sheddy Funster

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    I have had two twin USB outlets both running with an inline 5 amp fuse with no problems for a year or so, I also fitted a switch to each which stops them being powered and the led on when not in use.
    Cheers
    Ed
     
  7. PJGWiltshire

    PJGWiltshire Funster

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    Good idea thanks
     
  8. PeteH

    PeteH Funster

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    Mine has a nice blue LED, which is real handy for navigating to the "loo" at 2am!:D
     
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  9. Gellyneck

    Gellyneck Funster Life Member

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    Why have you got USB sockets fitted in your loo?:whistle:;):)
     
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  10. PeteH

    PeteH Funster

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    Obviously so I can charge the phone whilst texting?.:whistle::groan:
     
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  11. Pausim

    Pausim Funster

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    3.1 amps appears to be the output amps, the 12v input could well be different depending on the efficiency of the unit. Also on many devices you need to allow for an initial surge.
     
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  12. Richard and Ann

    Richard and Ann Funster

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    It's the wattage that determines the current draw.
    1a at 5v will only be 0.41a at 12v.
    P=VxI so Both equate to 5 watts
     
  13. Pausim

    Pausim Funster

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    Theoretically correct but that assumes a 100% conversion rate which is unlikely. I was careful to say only that it would be different, because of course I have no idea what circuitry is in use to make the conversion. I would hazard a guess that it will be highly inefficient. Also the initial surge current is unknown. If the advice that comes with the device says 10 amps it may be to allow for this.
     
  14. Richard and Ann

    Richard and Ann Funster

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  15. Pausim

    Pausim Funster

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    If that is the case 10A would seem overkill. I had not realised switched mode technology had reached these devices.
     
  16. wizzer59

    wizzer59 Funster

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    Jeeze guys, op stop reading now or else you'll get brain overload:confused:;):D
     
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  17. PJGWiltshire

    PJGWiltshire Funster

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    Indeed, great for everyone input it has been most helpful. I have the USB charger wired up on a 5A fuse, this will be linked to the media wiring circuit which has a 20a fuse. So just need to find a dry spell to wire it all in.
     
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  18. Chrysalis

    Chrysalis Funster Life Member

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    I wanted my twin USB charging sockets ( for smart phone and tablet) on each side of the bed so we could both have the devices in easy reach at night ( like we do at home). Our bed is over the "garage" so the panels on the two bedside tables are easily accessible from the garage side. There was already a 12 v socket in the garage fed from the 20A accessory fused outlet in the 12 v fuse box so I diverted this to a new 4-up 12v car type fuse box and wired one of these to the original 12v socket and two others to the two new double USB sockets. The fuses are easily changed in the box, but I have started with 5A ones as I have 11A wiring. The wiring is all concealed in matching trunking in the garage. The scary bit was drilling the 53mm dia holes in the bedside cabinets to install the sockets! I also have the blue LEDs but when not in use these are covered by flaps on the sockets. When in use a small piece of black insulation tape covers them.
     
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  19. wizzer59

    wizzer59 Funster

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    Why! is it outside? Or do you have a Swift?:giggler:
     
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  20. PJGWiltshire

    PJGWiltshire Funster

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    No got rid of Swift now have a Carthago. The area to wire into is in an outside storage box now the rain has moved on I can get things out and get on with it
     
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