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Thread: Question about ISOLATOR

  1. #1
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    Question about ISOLATOR

    Hi
    I am interesting installing in my car secondary battery for "In Car PC", And emergency kill off switch.
    I've search the web and found many options how to do it, But none of them fit my needs,,,
    I created a schematic diagram based on what I found, And would like to hear what you saying about it
    Regard
    Yogev
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  2. #2
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    That appears correct to me. In your diagram, that is a single Pac 80 isolator but you've simply shown both the + and ground side, correct?
    Quote Originally Posted by ghettocruzer View Post
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

  3. #3
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    No :S
    I draw one for the dual batteries, And one for the emergency cut off switch

  4. #4
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    I'm assuming the PAC 80 is merely a relay.

    Your ground isolator is an "Isolation Switch" as recommended for safety (ie,in the ground circuit), but it is NOT a kill switch.

    The +ve isolator is as typically used for parallel batteries. My alternator's charge-light output controls mine - hence my batteries are automatically connected when the alternator is charging (and disconnected when not).

  5. #5
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    Quote Originally Posted by OldSpark View Post
    I'm assuming the PAC 80 is merely a relay.

    Your ground isolator is an "Isolation Switch" as recommended for safety (ie,in the ground circuit), but it is NOT a kill switch.

    The +ve isolator is as typically used for parallel batteries. My alternator's charge-light output controls mine - hence my batteries are automatically connected when the alternator is charging (and disconnected when not).
    Mmm...
    Why the top isolator isn't act like a cut-off switch?
    I mean when I pull the small switch I will cut the ground and then I will shut off the car, Or do I? :S

  6. #6
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    Quote Originally Posted by XqG3X View Post
    Why the top isolator isn't act like a cut-off switch?
    Because the alternator will continue to supply +12V.

  7. #7
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    Quote Originally Posted by OldSpark View Post
    Because the alternator will continue to supply +12V.
    But I cut the ground, Although all the car component will have + they don't have -, Or I am wrong?

  8. #8
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    Yes, you are wrong.

    You break the ground to the battery.
    The engine is running and the alternator still spinning.
    Since the alternator is grounded to the engine end chassis, and its +12V output is still connected to the car's system (& battery +12V), the ignition and car is still getting +12V.

    You might burn out your electric loads by disconnecting the battery (because there is no battery to filter out HV spikes, or because it's an older alternator/regulator that uses the battery as a voltage reference), but you will not kill the engine.

    To use an isolator switch as an isolate and kill, it has to be inserted in the hot side (+12V) between the alternator & batteries on one side and the rest of the vehicle on the other.

    Usually mechanical switches are used in those situations. Relays are not recommended, else two or more are used in redundant configuration (separate fuses and circuits) and other safeguards to prevent false dropouts.


    Don't worry, I've had years of fun with the above.
    Whether it's watching people blow their electrics, fail scrutineering at competitions, or even arguing with the Regulators themselves... I've probably done it all.

    IMO a kill switch and isolation switch are two separate functions and should be kept separate. Most of the knowledgeable and experienced that are concerned with competitor safety have the same POV - they abhor "hot" isolation switches and dislike creating hazards that can damage people.
    But some competitions that don't know better insist on "isolate & kill" with a single switch and don't care that they drag an unfused heavy +12V battery cable through the cockpit (to the dash or console) and maybe even to a rear corner of a vehicle. Madness!!!

  9. #9
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    Ahhh, I didn't thought about the alternator thing like that....
    Can you please draw to me how to do the kill switch?

  10. #10
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    Usually kill switches short out the points or ignitor (output) - ie, ignitioncoil negative side to chassis/ground - but near the coil - not through long wires to elsewhere.

    Else they isolate ignition +12V, or injector +12V, or the EMS +12V supply.
    It depends on what you have.

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