Battery relocated to trunk, inertia switch?

Electrical and Ignition

  1. DionR

    DionR Well-Known Member

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    Been in the works for like 8 years now, finally getting my battery into the trunk with a remote cutoff switch.

    Not doing this for NHRA or anything. I just want to be able to walk away with the alarm system armed and no power forward of the trunk.

    Where I am struggling is with the rather large 1/0 battery cable running through the cabin and how to cut power on it in the event of an emergency like being t-boned. I know some will answer to use a Ford style starter solenoid, but that makes it much more complex and adds 2 more wires running up the side of the car (4ga power for the car and a start wire).

    The idea that crossed my mind was to use an inertia switch to trip the battery cutoff so that the cable is dead if something bad were to happen.

    Now most (all?) inertia switches are setup to disconnect a circuit in the event of an accident, but there are 3 pins, 1 power, 1 NC, 1 NO. My thought is to re-pin the connector so that I have a normally open circuit from the car side of the battery cutoff switch to the "off" pin on the battery disconnect. This would (in theory) create the function that if an accident happened the inertia switch would close the circuit and pulse a 12v signal to the battery disconnect and shut off the power but wouldn't leave power on the "off" circuit to burn up the disconnect.

    I'm no electronic wizard though so no idea if this even makes sense.

    Think it would work? Maybe a small capacitor just to extend the "off" signal long enough to insure the disconnect get's turned off? Or maybe a timed relay and power to the inertia switch from the battery side of the cutoff?
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    A battery cutoff is not normally a solenoid, because every time you parked the car, and did NOT kill the battery, the solenoid would be drawing current. Unless you are willing to deal with that, I don't know how you'd integrate a low current rollover switch with some sort of cutoff

    One thing I've considered is to use an "easy pull" cable such as a bicycle shifter. You can buy that cable and housing in bulk. Run the cable from the disconnect to say, between the front seats with an unobtrusive handle down "in" the carpet. You can just reach down and yank it and it will be "off"
     
  3. DionR

    DionR Well-Known Member

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    It’s a latching relay. Pulse 12v on one circuit and the relay closes and the car has power, pulse 12v on the other circuit and the relay opens and kills power. No power draw from the relay when it is closed or open, only when changing its state.
     
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    • Kendog 170

      Kendog 170 Let the boy go !

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      I myself like the ford solenoid as the main starter wire running inside my car is dead unless cranking. As for the Inertia switch I would look at a simple Ford Ranger switch that you could cut power to the electric fuel pump if your running one so in a rear end crash your pump shuts off. If not wire it to kill your ignition to kill the engine. Just my thoughts but believe me I'm no expert. I've thought of adding this valve near my tank and using an Inertia to activate it if I get rear ended, I have a fuel cell with rear ear exit fuel line where original tank was. (sorry no pic)
      https://www.amazon.com/dp/B007N0GRIE/?tag=fabo03-20
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      You have a link, part no. etc? Or even post a photo? Any inertia switches (that is OEM) are "latched closed" and open a circuit. So that would require a relay (or transistor etc) to invert, etc not sure how you'd implement that. Same problem, "draw on shutoff" Adding more circuit adds to possible failure, and defeat the purpose.
       
    • LJ67barracuda340

      LJ67barracuda340 Well-Known Member

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      Painless Performance 30206 Painless Performance Remote Master Disconnect Kits | Summit Racing mine shuts eveything down but the radio memory and the ECU
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      That is a continuous duty solenoid, and is not what Dion is talking about. What you posted is what I was referring to---it requires current draw to keep it alive if you don't shut it off every single time.

      If that thing REALLY is good for 200A it is one HELL of a continous duty solenoid, tho...
       
    • DionR

      DionR Well-Known Member

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      No, that is similar to what I am talking about. It kind of looks like a continuous duty solenoid but it only takes a 12v pulse to open or close the relay and doesn't require any power to maintain it's state.

      The website says "continuous duty" in the text, but the title is "latching" and the text also says "momontary push button":

      Painless Wiring

      "Our Remote Master Disconnect with Mechanical Latching Solenoid is ideal for everyday vehicle applications and is a simple and effective anti-theft deterrent. It uses a 100 AMP continuous duty solenoid which is activated by an easy to hide momentary push button. No risk of accidentally draining your battery with this latching solenoid. Kit comes complete with one solenoid, one switch, mounting hardware, wire and connectors."

      There are several kits out there that are similar.
       
    • DionR

      DionR Well-Known Member

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      It is a Parallax BR100

      Parallax Battery Disconnect Relay BR100 - RV Parts Express - Specialty RV Parts Retailer

      http://www.bestconverter.com/assets/images/Parallax/BR100/BR100install.pdf

      Interestingly, it says a latching switch to control the relay is ok. Maybe I don't need to worry about the inertia switch closing a 12v circuit for only a short time.

      Part of the reason I wanted something like this is because I wanted a relay that if I hit "lock" a couple of times with the fob, it just keeps opening the relay. The Painless one would toggle between open and closed each time you hit it.

      Yeah, not exactly sure how I would get past the "latched closed" issue other then a theory that they could be used in a normally open setup. The switches I have looked at have 3 pins, but only 2 are used. I am hoping the third unused pin could be used to close a circuit. Planning to snag one at the wrecking yard to play with this weekend to see if it is true.
       
      Last edited: Apr 8, 2021
    • DionR

      DionR Well-Known Member

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    • DionR

      DionR Well-Known Member

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      I understand, and don't disagree. It just seems to add a level of complexity that I want to avoid.

      I might add that you still have a charge wire running up the inside of your car and while it might not be 1/0 gauge, I bet it is still big enough to catch something on fire in the same situation I am working to avoid. So the Ford solenoid really doesn't fix the issue. Well, except that you can fuse the smaller charge cable much more easily.

      That is certainly the most common use for an inertia switch. I currently don't have EFI or an electric fuel pump (but it's in the works), killing the motor still doesn't fix the issue of a rather large cable hooked to the battery.
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      OK Dion here is what I "believe"

      The Parallax seems to be just what you said.......pulse on, pulse off. The Painless/ Summit versions are a bit of a "dirty trick" They are using a rather STANDARD (LOL if there is one) type of continuous duty solenoid and they are ELECTRICALLY latching it on by feeding power back from "it's own contacts"

      If that Parralax devices is as good as claimed it is one hell of a setup

      http://www.bestconverter.com/assets/images/Parallax/BR100/BR100install.pdf

      This page claims they are 100A continuous, 300A surge for 30 sec

      BR 100 Series Accessory – Parallax Power Supply

      Same outfit/ supplier you posted has some heavier ones, too

      Battery Disconnect Relays Archives - RV Parts Express - Specialty RV Parts Retailer
       
      Last edited: Apr 8, 2021
    • DionR

      DionR Well-Known Member

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      I think the Painless kit uses a Cole Hersee 24200 relay. I though I had a sheet on it and how it worked, but can't seem to find it now.

      Cole Hersee 24200 SPST Latching Solenoid 12V 110A Continuous Duty

      There are actually better ones.

      The Intellitec 01-00055-000 is actually rated at 500 amps for 30 seconds. But the circuit is reversed to open or close it rather than having two separate circuits.

      Intellitec 01-00055-000 Relay, 0100055000

      And if you really wanted to go all out, I would use this one:

      300 Amp Disconnect | Buy a 300 Amp Battery Disconnect Switch for Street Rods from Watson's StreetWorks
       
    • LJ67barracuda340

      LJ67barracuda340 Well-Known Member

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      Incorrect, it is a latching solenoid. No draw
       
    • LJ67barracuda340

      LJ67barracuda340 Well-Known Member

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      Yes
       
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      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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      • DionR

        DionR Well-Known Member

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        For what it's worth, I have a Cole Hersee 24200 that I bought before I found the Parallax relay. It is a dead ringer for the relay in the Painless kit. Even the printing on the bottom that is easier to see when zoomed in using the Summit kit. Not saying I can read the text in the image, only that it is close enough that I think it says 24200 and 12VO46M just like the one in my hand. Even the same brass nuts and white insulators.
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        Don't forget that on a one wire, SPST cut-off system, if you cut the battery power with the engine running, the system continues to run just fine on the alternator, until you also cut the field circuit.
         
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        • DionR

          DionR Well-Known Member

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          Not looking to kill the motor with the switch. Not going to be an NHRA approved install and don't want a 4 pole switch in the trunk I have to pop the deck lid to get to and a wrist sized bundle of wires running up the side of the car.

          Just want to drive it to dinner and have a better chance it will still be there when I come out. Nothing is perfect (including the new 2.8hp setting on a Hellcat), but it's better.

          Just figured if something did go wrong, be nice to have an added measure of safety in case the big wire got pinched. Granted, until the motor is turned off the wire is still hot from the Alt end, but right now that (at best) 60 amps and I can add a breaker when I go to the Magnum EFI and bigger Alt later.
           
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          • DionR

            DionR Well-Known Member

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            Based on this, looks like a three wire inertia switch does have a contact that is NO and closes in an impact.

             
          • 67Dart273

            67Dart273 FABO Gold Member FABO Gold Member

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            I'd say you have found it, Dion. the switch I mean. I was going to point out that there are other kinds of inertia swithes for other than auto use, but trying to engineer what force, etc this one is already "there.". About all you'd have to do is mimic the mounting orientation in whatever it came out of
             
          • LJ67barracuda340

            LJ67barracuda340 Well-Known Member

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            I have that switch from a Taurus. I think the button faced up
             
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            • DionR

              DionR Well-Known Member

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              Good point. I was just looking for a cheap option that I could easily find, didn't even think about the fact that I could end up with something designed for a different application that didn't work well.

              Yup, red button straight up.

              I am going to wire it into the same relay circuit that the fob triggers to open the BR100. I was thinking about trying to mount it somewhere where I could reach it if it trips due to a bad bump or something, but for now I think I will just mount it in the trunk where I can easily reach it. If it because a nuisance, I will just unplug it and look for a different solution.
               
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              • 67Dart273

                67Dart273 FABO Gold Member FABO Gold Member

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                You can certainly parallel another switch in to manually release
                 
              • LJ67barracuda340

                LJ67barracuda340 Well-Known Member

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                When I used to go on trips with my Taurus and park at a motel or somewhere I used to go in the trunk and trip the inertia switch. You have to give it a pretty good wack to make it trip out. Dont laugh,,, it had nice wheels. LOL
                 
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