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Car stereo 12v ignition current draw

Discussion in 'Electronics' started by M.A.94, Apr 11, 2017.

  1. M.A.94

    M.A.94 Hardcore MB Enthusiast

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    How safe is it to share the cig lighters power with my car stereo 12v ignition power without an additional fuse.

    Am I correct in thinking that the 12v ignition (red wire) is effectively like a remote turn on lead on an amp and therefore the current draw is very little.

    And the constant 12v (yellow wire) is what gives the unit it's power.
     
  2. bob6600

    bob6600 Hardcore MB Enthusiast

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    The cig lighter feed is fine for an after market stereo.
     
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  3. OP
    OP
    M.A.94

    M.A.94 Hardcore MB Enthusiast

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    Brilliant. Is this even when taken into account I charge my phone using my cig lighter often and chances are the stereo will be running simultaneously
     
  4. markjay

    markjay Hardcore MB Enthusiast

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    Cigarette lighter fuse is typically around 15A - you are highly unlikely to overload it. Your phone will draw between 0.5A to 2.1A max. Ideally you will add a second fuse for the phone charger with a 3A or 5A fuse - unless the charger already has a built in fuse. The same for your aftermarket HiFi - ideally you would want it protected with a dedicated fuse with lower rating than the cigarette lighter fuse. Said that, if you don't fit second fuses, everything will work fine as long as the connected devices don't malfunction and start drawing too much current. So the issue isn't overloading, instead the (potentiall) issue is not having a low-rated fuse protecting the devices.
     
  5. OP
    OP
    M.A.94

    M.A.94 Hardcore MB Enthusiast

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    Thanks MarkJay makes a lot more sense the way you have explaned it. I have however already done the wiring before checking this thread and done it without additional fuses. May just leave it as it is for now.

    The issue I was having was originally my unit was wired in with both switched and constant power going directly to the battery and thus as far as the unit is concerned the ignition is always on. It didn't bother me having to turn the unit off manually everytime I turned the car of in order to keep the battery charged. However recently I brought an ipod adapter for my unit and the way alpines ipod connectivity work's is that it basically charges the ipod regardless of whether the unit is turned on or off, it's only when it detects the ignition is of that it would stop charging. I didn't like the idea of my ipod battery constantly being on charge over night and throughout the day so had no option but to find some sort of switched power.
     

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