Battery cut off switch

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    Battery cut off switch

    Moving battery redoing cut off switch. Got to wondering about putting switch on negitive side rather than positive. Is this going to be a bad idea?

    #2
    Negative. It's positively not a bad idea

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      #3
      it's a good idea

      current flow direction is opposite the flow of electrons (from - to +) so I always disco the neg

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        #4
        Interesting. I've always put cutoff on the positive, though I don't really have a reason why, that's just what I've done.

        Negative kinda makes sense though, any time I'm working on the electrical system I always pop off the negative cable, not the positive.
        - Buck

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          #5
          Originally posted by dnsfailure View Post
          Interesting. I've always put cutoff on the positive, though I don't really have a reason why, that's just what I've done.

          Negative kinda makes sense though, any time I'm working on the electrical system I always pop off the negative cable, not the positive.
          When I was removing the cutoff it occured to me that it would not take much to create a short at the switch. Thinking that having it on negative will prevent that from happening.

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            #6
            +1 on the neg. Side
            You create an arc breaking the hot lead.
            plus NOTHING works without ground..
            83, 22re,w56,ultimate duals,4:10 \31" arbs.
            hopes to grow up someday

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              #7
              (Quote) stolen but this is what I've heard and have done on drag cars.
              Joined: Jun 5, 2005
              Posts: 1,282
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              from Oak Park IL
              I have mine on the positive side. If i remember right, that is how the NHRA rule book states it to be installed. You must also run your alternator feed between the battery and the switch so when its in the off posission it will kill the power to the hole car, including the engine. If you put the switch on the ground side of the battery the engine would continue to run, as it doesnt need battery ground.


              SEP 27, 2007 (Quote)

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                #8
                If
                I
                Remember
                Right????
                83, 22re,w56,ultimate duals,4:10 \31" arbs.
                hopes to grow up someday

                Comment


                  #9
                  Always disconnected the negative side of the battery if your trying to kill all power. If some of your electronics have capacitors or small battery cells built in they can still flow electricity if the just the positive side of the battery is disconnected.

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                    #10
                    In most forms of competitive motorsports the battery switch MUST be tied in to the positive side of the battery and alternator charging wire to meet the rules. As someone stated above, if its tied into the negative side, once the engine is running the battery switch won't do shit to turn off the electrical system. It is installed on the positive side so if there is ever a crash ect and fuel lines get ripped open the pumps and engine will not stay running when the switch it turned off. It's for saftey.

                    If all your looking to do is add one on to keep a battery from discharging, go on with your bad self and install it on the negative terminal.

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                      #11
                      I'm not so good with electronics. If a motor could still keep running without being grounded (I assume it would die pretty quick after though, if it has electronic fuel pump?), could you push-start a car that's not grounded?
                      - Buck

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                        #12
                        Originally posted by dnsfailure View Post
                        I'm not so good with electronics. If a motor could still keep running without being grounded (I assume it would die pretty quick after though, if it has electronic fuel pump?), could you push-start a car that's not grounded?
                        Nope. As long as the engine is running and the alternator is charging it will never shut off.

                        You have an older car or truck? If so, go start it up and take the battery cables off while it's running. I bet you it stays running until it runs out of fuel.

                        NHRA, NASCAR, ect all require it to be wired in to the posititive side for this reason.

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                          #13
                          Originally posted by SLOWPOKE693 View Post

                          Nope. As long as the engine is running and the alternator is charging it will never shut off.

                          You have an older car or truck? If so, go start it up and take the battery cables off while it's running. I bet you it stays running until it runs out of fuel.

                          NHRA, NASCAR, ect all require it to be wired in to the posititive side for this reason.
                          Mine are diesel, so they run without a battery regardless

                          That makes sense with the alternator, I guess the distributor doesn't need ground to make spark then? I know magneto distributors will spark on their own.
                          - Buck

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                            #14
                            All my heavy equipment the shut offs are on the negative side. That way when you run the volatage down you don’t run a bijillion Amps through the switch, instead you just burn the cables off at the starter.

                            fwiw cat makes a awesome keyed shutoff that holds up forever. I got like 40 of them in service and the only reason I had them fail is the keys rusting in them from the lack of use.

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                              #15
                              Originally posted by ThePanzerFuhrer View Post
                              All my heavy equipment the shut offs are on the negative side. That way when you run the volatage down you don’t run a bijillion Amps through the switch, instead you just burn the cables off at the starter.

                              fwiw cat makes a awesome keyed shutoff that holds up forever. I got like 40 of them in service and the only reason I had them fail is the keys rusting in them from the lack of use.
                              For my current project, I picked up an old porsche cutoff switch, where the handle to the switch comes off when it's shut off. I like it because it looks different than the standard Moroso style switches. The only problem though, is that when you turn it off, the handle/key literally just falls out. So you can't leave it in there if you want to.

                              Does the CAT key stay retained somehow when it's turned off? or do you have to remove it every time like this one?


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                              Last edited by dnsfailure; 06-09-2020, 10:16 AM.
                              - Buck

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