DC to DC circuitry from Car Battery

Discussion in 'The Projects Forum' started by des sd, Mar 18, 2011.

  1. des sd

    Thread Starter New Member

    Mar 18, 2011
    2
    0
    Hi guys,

    Am working on a design to use a car battery to power up some equipment (phone, wifi etc). With the limited amps from the cigarette lighter, I was thinking of using a direct cable from the battery to the circuitry. I have attached a simple diagram with my idea and have been toying with the use of zener diodes and even 7812 ic's to do this but am stumped. Really hope that someone can advise.

    It looks simple enough but am having a challenge with the fluctuations and insufficient wattage coming out of the lighter head. Thanks in advance!
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    You need to construct (or purchase) a few DC to DC converters and wire them directly to the battery. Some of the smaller loads can come from the cig lighter if you wish.. But I'd just feed them all from the same spot.. Don't forget fuses.
     
  3. des sd

    Thread Starter New Member

    Mar 18, 2011
    2
    0
    thanks mcgyvr, I was thinking of a direct connection too to the car battery. But how do I prevent the initial surge from the car battery from burning out the equipment and also to prevent incorrect connections (+ve and -ve points)?
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    I don't think you should wire direct from battery,as this is fairly dangerous.

    Besides the lighter output can handle fairly high current. It is enough to run even a low power car stereo. Ur phone and wifi is nothing compared to that.

    {ed}
    I checked the diagram. You wanted 24V. If so then the lighter out is out of the question.

    U need care when putting wire through fire wall. If you try to put a hole in the firewall, this thread will be locked as we do not encourage such practice to anyone. Aftermarket wire routine should be done if you know what you are doing.
    Bad fuse ratings and under gauge wiring will definitely can cause fire accidents.

    Unless you can tap into the stereo harness, there is nothing much we can do. Even this is possible running a 24VDC converter s out of the question as this circuitry will draw a lot of amps. But mostly depend on ur 24V load.
     
    Last edited: Mar 28, 2011
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,789
    945
    The auto makers were kind enough to put an 'accessory' position in the fuse box. Many of them are fused and many also offer the keyed, or ignition switch on, only wiring points.

    I strongly suggest you use the ign. switched mode. Meaning the accessory point in the fuse box which has voltage when you have turned the key to the first 'click', but not yet started the car. It allows a person to use an electric device while they are in the car, but disconnects it from the battery when they and the key are removed from the vehicle.

    A meter and a few minutes checking/mapping the fuse panel with the car running, with it switched off but key turned on, and when the key is fully removed is all that is needed. If the wiring point can't be found in the box, so that a fuse can be added to complete the connection.

    Connect directly to battery...AT the fuse panel.

    Connections to the battery corrode quickly. The wire can break, and then short somewhere directly to the grounded chassis. If it is possible, it will happen to somebody, somewhere, so DON'T DO IT! be safe, batteries are 'energy bombs' when all the power is short circuited. Nothing good can happen, so avoid the risk. Hook to the fuse box and then PUT A FUSE in your wire, complete with matching fuse holder.



    http://www.powerstream.com/dc-2171.htm

    http://www.astrodyne.com/google/dc-converter/?gclid=CJyb2Lbe8KcCFchJ2godKz-ddA
     
    Last edited: Mar 28, 2011
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,010
    1,530
    Cigarette lighters are connected by a fuse (usually 20-30 amps) directly to the battery. They are not switched by the ignition.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    This is not always the case. Some of the vehicles I've owned were switched, some were not.
     
  8. wayneh

    Expert

    Sep 9, 2010
    12,120
    3,046
    Correct: My Chrysler minivan has one of each, side by side, clearly marked with a key icon and a battery icon. It's a great convenience IMHO, to have that choice.
     
  9. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,010
    1,530
    SgtWookie and wayneh - These would be in newer cars, right? I think your confusing what they are now calling, 'power ports' with a cigarette lighter. The outlet looks the same but is switched. A cigarette lighter is unswitched. The one in wayneh's case that has the key symbol is a 'power port' and the one with out is a lighter. Both the same thing except for the connection to the switch.
     
Loading...