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Thread: Question about ISOLATOR

  1. #11
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    But if I want permanently stop all the electricity in my car (In case of a short), You say it isn't possible to do it by opening just one connection? (using only one switch/relay)

  2. #12
    Raw Wave
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    That's called an isolation switch. The best is how you have it in your diagram - ie, the top right isolator in the ground - although it's usually a switch, not a (single) relay.
    That battery -ve to to chassis/body/engine switch isolates battery power from the rest of the vehicle vehicle.

    What I said was that that will not KILL the engine if it is running.

    A Kill Switch kills (stops) the engine.
    An Isolator (switch) isolates the battery.
    They are two different functions (though some IMO silly people try combining the functions for general use).


    Usually fuses or circuit breakers are used to protect from shorts - not switches.

    And as I hinted, if an "isolator relay" unintentionally opens....


    Why not say what you hope to achieve, why you want to do it, and under what circumstances?

  3. #13
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    Thanks for your reply,
    I just try to create emergency switch for my beginner race car.
    And I thought that the "kill switch" should stop the engine and shut off all the electricity,
    But with your explanation I understand my confused...
    Again thanks for your reply, What I gonna do is just put a on/off switch on the (+) line between the fuse box and the ECU.
    Regards
    Yogev

  4. #14
    Raw Wave
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    Cool!
    Don't worry - in my experience, even those that made the rules were confused.

    Some said an ISOLATOR had to kill the engine AND isolate ALL loads including the starter motor and alternator. Some said it could be done with one full-current carrying switch but there were and still are wrong!

    Some said an ISOLATOR (that didn't kill) had to be in the +12V side. They were just fracken IDIOTS, and they still are if they believe that to be "safe"!!! (And efficient!)


    I promoted and argued for isolation switches to ONLY be in the ground circuit - ie, between the battery and everything else. Especially when a dash switch or "rear corner" switch was required.

    I promoted kill switches as a separate switch and function. Think of motorbikes - they (almost) all have kill switches to kill the engine, but this does NOT cut power to the bike. Why? It should be obvious with a bit of thought.


    If a SINGLE switch is to CARRY the power and both isolate battery power AND kill the engine, then it has to be in the +12V side with the battery & alternator on one side, and everything else on the other side. But that means the isolator does NOT isolate the alternator from the battery. (The starter should be the downstream "switched" side, but some didn't care. LOL - Idiots!)

    If a single switch is to CONTROL kill & isolate switches, then ground isolation can be used - but that means the switch controls a relay that isolates and a relay that kills (similar to your circuit in the OP).
    For various reasons, this is rarely specified - in fact it is often PROHIBITED.
    [ It requires multiple redundant relays and paths for reliability. The isolation relay must be energised to connect power and the kill relay must be energised to NOT kill the engine, hence with both relays de-energised, the engine is killed and the battery is isolated. A broken relay or connection can thus be very dangerous, hence dual parallel relays are often used. And for the pedantic, how do energise a relay without power? ]


    To summarise, the preference is always for the power (battery) isolation to be in the -ve (ground) circuit for safety's sake, and hence the kill switch as a separate function and circuit.

    But some regulations require the battery isolation switch to both isolate and kill. That compromises safety, but one assumes the Regulators have done their Due Diligence else await possible law suits.


    You need to find out what the regulations stipulate where you intend to race.
    And if it asks for an "Isolation" switch, check its definition.
    Allegedly all except one competitor failed a local National event's scrutineering when its Regulations defined "Isolate" to mean "Isolate and Kill". Stupid I know, but "them's the Regs"! (Like Resistance, Argument seems Futile (to Regulators)! Even court findings are simply dictated and not argued LOL!)

    I'll see if I can manipulate a diagram to show the two main scenarios. The one I have is proprietary.


    And if I am out of touch with recent regulation changes or isolation methods, or if anyone reckons those morons aren't the idiots I suggest they are, please chime in.
    (I know there are a few instances where a single power-carrying "isolate and kill" switch or "remote" control via relays is justified, but AFAIK these do not cover typical "public" racing events and competitions.)

  5. #15
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    Hi, Thanks for all your advices, You helped me alot
    Regards
    Yogev

  6. #16
    Raw Wave
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    My master provided a diagram....

    Hopefully it is self explanatory.
    As it says, only the RHS version (with alternator connected to the battery) will both kill the engine AND isolate the battery (but not from the alternator).

    The 2 RHS methods are NOT recommended if a +12V short to chassis/body/GND is to be avoided.
    The starter motor should also be isolated (hence why isolator switches are rated for several hundred amps short-term use), though the starter motor is shown as battery connected in the RHS diagram - apparently that was to avoid confusion!?.

    The only "truly safe" isolation (even if the isolator is next to the battery terminal(s)) is the ground isolation as shown on the 2nd left "Cold Isolator" (Recommended) diagram.
    (The first diagram merely depicts a standard vehicle's power distribution.)

    And "battery" means "total battery" - ie all batteries are paralleled as a single battery with respect to the terminal (polarity) being isolated. (Hence too the recommended solution - normal "inter-battery isolators" can operate normally.)
    FYI - strictly speaking, "battery" means "all batteries" - a battery is made up of a cell or cells, monoblocks, or strings of batteries. What we call a battery is usually a "monoblock" in tekland.


    Questions or concerns? Just ask....



    Thanks again ImageShack.us!

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