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Automotive cable

  • 09-06-2011 9:15am
    #1
    Diggerdunne
    Registered Users, Registered Users 2 Posts: 431 ✭✭


    Does cable used to wire cars have the same properties as domestic t&e. As in is 1.5 t&e the same as 1.5 automotive cable?


Comments

  • #2
    DublinDilbert
    Registered Users, Registered Users 2 Posts: 5,401 ✭✭✭DublinDilbert


    Diggerdunne wrote: »
    Does cable used to wire cars have the same properties as domestic t&e. As in is 1.5 t&e the same as 1.5 automotive cable?

    Yes and No I guess is the answer to your question.

    Typically domestic 1.5mm (& 2.5mm) cable will be solid cored. Nearly all cable used in cars would be stranded, to allow for flexibility on install and in use. Also being stranded is easier to terminate in crimp style terminals.

    The very odd time they will also use the likes of Teflon insulation, if its in a high temperature area of the vehicle, but typically its just PVC insulation.

    Do you need much cable? I have a roll with some stranded 1mm sitting here (http://radionics.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=356729&x=0&y=0)


  • #3
    Diggerdunne
    Registered Users, Registered Users 2 Posts: 431 ✭✭Diggerdunne


    Thanx but don't need any. Was just been curious. I was just thinkin 5 amps at 12v as opposed to 230v at 5 amps do the cables have the same properties etc...


  • #4
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Automotive cable is also stranded to make it more resistant to vibration. Even the domestic cables that are stranded just have 7 strands, where a car would have many more for the same size cable to make it more flexible.


  • #5
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Diggerdunne wrote: »
    Thanx but don't need any. Was just been curious. I was just thinkin 5 amps at 12v as opposed to 230v at 5 amps do the cables have the same properties etc...

    5 amps at 12 volts will have identical effect on the cable as 5 amps at 230v. No difference at all.

    The difference is at 230v, the 5 amp load will have a resistance of 46 ohms. At 12v it will be 2.4 ohms. So the 230v load will be 1150 watt, where as the 12v one will be just 60 watts. But the volt drop in the cable will be the exact same for both loads if the same length and size of cable is used, excluding the fact its AC at the 230v situation. This also shows the percentage power lost in a cable is higher at lower voltages for the same power load on the same size cable.

    This is why you will see that 1 kw at 230v is only 4.5 amps, but at 12v its about 83 amps. This can cause confusion for some, thinking that connecting the 12v 1kw heater to 230v will now only draw 4.5 amps to still be 1kw, because they hear the higher the voltage the lower the current for the same power, but the load has a design resistance to be a given kw power at its design voltage. The 1 kw 12v load will actually draw 1590 amps if connected to 230v, which in reality would be practically a short circuit on 230v.

    So a 1kw heater for 12v use would have a far lower resistance than a 1kw heater at 230v, and will only be a 1kw heater when connected to 12v, it would be a 4kw heater when connected to 24 volts (but would burn out as its only designed as a 1kw heater).

    As such, a 1kw 230v heater would need a far smaller cable than a 12v 1kw heater.


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