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  • Battery Quick Disconnect Question

    I've been doing a fair amount of wiring-related work on my TR6 (more questions to post on THAT) and after seeing many pics of folks with the green knob quick disconnect thingy, I jumped in and spent my $9.95 for one. I had an idea how it worked and saw a vid or two showing how a simple few twists will isolate the battery's negative terminal from the chassis. My experience so far is that the pressure exerted by the negative cable after numerous adjustments will cause the knob to still maintain at least an intermittent connection. So, I've been completely unscrewing the knob and pulling the lead away from the battery to assure no contact is made. For those with this disconnect, is this how you're using the device? It's still simpler than loosening the clamp from the terminal, so there is an improvement, but I really like the thought of a few twists getting the job done.

    Any insights?

    1975 TR-6
    CF39057 U
    Pimento Red

  • #2
    There must be something wrong with your unit, maybe with the plastic insulator. These items are pretty cheaply made of pot metal, and I doubt that they are even tested by the manufacturer.

    Ed
    Last edited by ed_h; 03-18-2021, 07:54 PM.
    For just a little more, you can do it yourself!

    Comment


    • #3
      Ed,
      So, it sounds like a few twists work for you? I opted for the green knob unit because that's what I saw most of in folks' pics and I assumed they're of similar quality, but perhaps the one I got is subpar. I've enclosed three pics to show the situation. Perhaps there is a better unit out there which will have less slop in it? There's no twisting position that maintains separation.


      Knob closed, connection made
      Click image for larger version

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      Several twists and holding the cable side of unit parallel to maintain a broken connection.
      Click image for larger version

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      Twisted "open" but even slight pressure from negative cable causing loose knob to contact battery side of unit.
      Click image for larger version

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      1975 TR-6
      CF39057 U
      Pimento Red

      Comment


      • #4
        I recall several threads over the years regarding this problem. For that reason, I always remove the negative terminal connection from the battery, when the car will be sitting for a spell (also prevents potential drain from unrecognized sources), and ALWAYS when car is parked inside a garage, due to the potential for fire.. Perhaps nothing worse than a switch which may work some of the time.

        Comment


        • #5
          FWIW...I tried one of those 10 dollar jobs myself. Like Jackamo I found it unreliable. I just gave up on the idea.

          Driving a 1973 TR6
          Doing ZS carb repairs
          email kencorsaw"at"aol.com

          Comment


          • #6
            I have two of those on two cars, they work great. It’s not rocket science. The shoulder on the knob contacts the top floating plate and makes the connection to the bottom threaded plate. They have a plastic insulator between them. Tight makes it a solid connection through the threads. So, if you exert a downward load on the top plate with the cable, it will contact the shoulder and make a connection. The 4A works fine as in the picture below. With the 6 I had to attach the battery cable from the bottom and put a bend in the cable at the shelf so that the cable itself does not pull or push the plate when the knob is loosened, it just floats there. If you can’t get the cable to float, just unscrew the knob a few more turns until it doesn’t contact the top plate. Quite simple, yet effective.
            Last edited by lfmTR4; 03-18-2021, 01:17 PM.
            72 Pimento w/overdrive - Lilred
            67 4A Royal Blue - Lilblue

            Comment


            • #7
              Thanks for the inputs, guys. Think I’ll stick with the unit and completely separate the halves.
              1975 TR-6
              CF39057 U
              Pimento Red

              Comment


              • SapphireBlue72
                SapphireBlue72 commented
                Editing a comment
                I bought one. Found that the two pieces had to be separated completely.
                No amount of turning the knob created a disconnect.

                There are different designs of this cable-to-post disconnect- it is hard to tell them apart from an internet picture.
                Some of them (the more expensive ones?) get the job done without separating the two halves.

            • #8
              Had the cheap (2) green knob (made in China) not reliable one. Someone recommended this one, black knob, with the American flag,(made in USA). Works smooth, with positive disconnect and well made.
              https://www.gamainc.com/product/bs200/

              Comment


              • #9
                Originally posted by Jackamo View Post
                Ed,
                So, it sounds like a few twists work for you?
                Mine is actually a custom one, but it is based on the same design, so there is nothing wrong with the design, just the execution. The American made one may be worth a try.

                Ed

                I used the green knob from one of the $10 ones.

                For just a little more, you can do it yourself!

                Comment


                • MRankin
                  MRankin commented
                  Editing a comment
                  Thanks Ed- Group 34R AGM battery. Exactly what I will use. We were thinking the same thing. For as much time as I have spent reading your TR6 pages I had yet to peer into the battery/cable write up you had. Yes quite impressed with your custom post clamps and 3D printed red post clamp cover. Top notch sir! Cheers.

                • jcruze
                  jcruze commented
                  Editing a comment
                  Ed, your neg disconnect and positive battery clamp are a great design and seem to solve a lot of problems with multiple taps and a clean look. You could probably sell a ton of these. Have you given any thought to manufacturing?

                • ed_h
                  ed_h commented
                  Editing a comment
                  Not really. The difference in effort between a one-off part and a production process is huge, and I'm still pretty busy wit my GT6 restoration. I'll never say never, but no plans right now.

                  Ed

              • #10
                I have both the green one sold at Walmart and the black one off Amazon. They are pretty simple devices and both work fine if you are mindful of the top cocking with cable weight and making contact with the knob when disengaged. If you can't relieve the weight a few more turns of the knob might be needed to widen the gap. Ed, your signature says it all
                72 Pimento w/overdrive - Lilred
                67 4A Royal Blue - Lilblue

                Comment


                • #11
                  On my two disconnects the two plates barely move if any and they shouldn't touch. They are separated by a plastic insulator that comes up into the bolt hole of the top plate. Its the bolt or knob that when unscrewed breaks the connection between its threads in the bottom plate and the shoulder to the top plate. The connection is through the bolt. When the top plate starts separating from the plastic is when you run into problems with it cocking and touching the shoulder on the bolt as you can see in Jacakamo's pictures. It may help to glue the brass plates to the plastic to keep everything in place and parallel since it's the bolt's shoulder that makes the connection.
                  Last edited by lfmTR4; 03-19-2021, 04:20 PM.
                  72 Pimento w/overdrive - Lilred
                  67 4A Royal Blue - Lilblue

                  Comment


                  • #12
                    My experience with cheap green knob battery disconnects on cars and boats have led me to the conclusion that they don’t last as long as one might hope.

                    The ones with the red keys are much better, plus they work as a casual anti-theft device, especially when you misplace the key in your garage. Check on Pegasus Racing or Summit or Jegs.
                    Last edited by UberXY; 03-19-2021, 05:03 PM.
                    SR
                    73 TR6. HT/AC/OD
                    86 930
                    91 535i

                    Comment


                    • #13
                      I've been using the same green knob unit for about 20 years, first on my 1960 Buick and then on the 2 TR6s that replaced it. I think I paid $4 for it. It has worked perfectly the entire time. However I can imagine that if it is over torqued it would go bad pretty quick.

                      Comment


                      • #14
                        I too have a green knob cut off about 18yrs old. I always removed the knob to cut the connection. I never pulled out the slide in part. Never trusted just un-screwing the knob a few turns. Removing the knob is still way easier than removing clamp from the neg post.
                        MRankin
                        71 TR6 CC61212L

                        Comment


                        • #15
                          I just received the US Flag, black knobbed quick disconnect and it’s night and day compared to the sloppy green knob that I first bought. Three half twists from engaged and a no slop disconnect is maintained. Much happier.
                          1975 TR-6
                          CF39057 U
                          Pimento Red

                          Comment

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