No announcement yet.

Question about ISOLATOR

  • Filter
  • Time
  • Show
Clear All
new posts

  • Question about ISOLATOR

    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
    Attached Files

  • #2
    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?
    Originally posted by ghettocruzer
    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
      No :S
      I draw one for the dual batteries, And one for the emergency cut off switch


      • #4
        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
          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).
          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
            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
              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
                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
                  Ahhh, I didn't thought about the alternator thing like that....
                  Can you please draw to me how to do the kill switch?


                  • #10
                    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.


                    • #11
                      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)


                      • #12
                        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?


                        • #13
                          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.


                          • #14
                            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.)


                            • #15
                              Hi, Thanks for all your advices, You helped me alot