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Thread: how many amps to start the car.

  1. #1
    Constant Bitrate minghi's Avatar
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    how many amps to start the car.

    hi

    i am trying to find out how many amps would pass through the battery cable when starting the car. is it the same as 650 Amps (battery rating for cold cranking amps).

    what do remote car starters use (relays????) to start the car. i am kinda designing my own security system for the car, so wud really appreciate some suggestions.



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  2. #2
    MySQL Error Scouse Monkey's Avatar
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    I would rpesume they jsut use the existing relays and are simply like having a second ign barrell running in parrallel - that is how i would do it.

    ie use relays to simulate the key posiitons in the ign.

  3. #3
    FLAC shakes's Avatar
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    the exact number will depend on the car, weather, etc. it's in the upwards of 100a or more.

    if you're asking so you can size your relays the amount of current flowing during startup doesn't really matter. AFAIK The relays used in remote start systems just activate the starter ... but the starting current doesn't actually flow through the relay.

    I could be wrong but that's how I understand it.
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  4. #4
    MySQL Error Scouse Monkey's Avatar
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    yeah i heard that but surely there must be a realay someehre between the battery and the starter. There is no other way.

    hang on, will go find my hanynes book..


    ...right on my pug 306, which is the bestest and most relaible car inthe world an will own you all - hehe....

    ...there is a 'starter inhibitor relay' conencted to the starter...but the starter is wired dircect up the battery +ve and earth. The inhibitor is also connected to the motor and would appear to simply ground out the motor or something and prevent it from activating. ther is also a 'starter inhibitor switch' which activated this relay and both the realya nd the switch are conencted to the ign barrel.

    I sold strongly suggest you get hold of the electrical wiring system diagrams for your car and fully understand them before messing with anything.

  5. #5
    FLAC shakes's Avatar
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    yeah you definately need a schematic .. but that's generally how the starter works. the relay completes the connection with the starter so the engine will crank.

    that's how you can start a car by shorting a screw driver across the starter ... that's how one of my old friends used to start his car every day :-) (and yes, it was HIS car ... or so I think it was)
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  6. #6
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    Yep. I installed a remote starter on my wife's car and it used little bitty relays. They just mimick the action of turning the key. They heavy electrical power runs through the car's starter relay and circuit.
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