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Battery disconnect

Discussion in 'The Hokey Ass Message Board' started by Hotrodmyk, Mar 27, 2013.

  1. BootleggerMatt
    Joined: Aug 17, 2011
    Posts: 258

    BootleggerMatt
    Member

    Everyone that still thinks power is flowing through your car looking for a ground after you disconnect the negative cable, I give you this task. Go outside, touch the positive post on the battery. Did you get shocked? Why not? Are you confused? Now if you still don't understand, go ahead and touch the negative post while still holding onto the positive post ;-)
     
  2. Carter
    Joined: Mar 18, 2006
    Posts: 1,406

    Carter
    Member

    Still waiting to hear the answer to this one. Paging Weasel, paging Weasel.

    Sent from my DROID device using the TJJ mobile app
     
  3. Weasel
    Joined: Dec 30, 2007
    Posts: 6,694

    Weasel
    Member

    Okay, Weasel chiming in: a little known and somewhat obscure issue with GM alternators is that they do, under certain conditions, backfeed. In this instance the alternator was backfeeding to the electric fuel pump, even though the ignition was off, key pulled from ignition and HD master cutout switch turned off. The plug wires were pulled off the engine and the HT lead disconnected as well, but the engine was hot enough to be glowing or dieseling. As long as the alternator continued to supply electricity to the fuel pump and the engine would ignite the mixture, it would continue to run - as it did for ten minutes or more after everything was shut off. The only solution was to starve the carburetor of air by pulling off the blow through supercharger hat and stuffing rags down it. By this time the engine was literally toast and it was a very dangerous situation as it could have seized and let go at any moment. Painless Wiring recognizes this alternator backfeeding issue and has a kit to prevent backfeeding. I would strongly urge that this is a must have safety device.

    Painless has this to say:

    This kit, complete with 250 amp solenoid, will effectively handle alternator feedback of the highest amperage alternators. Eliminates engine run-on when the master disconnect is turned off. Alternator feedback can keep your engine running even with the master disconnect turned off - this kit eliminates engine run-on. Highly recommended by most racing sanctioning bodies. Easy to install with all hardware and instructions.

    Linkee....

    www.painlesswiring.com/webcatalog/largeview.php?SearchField=50105
     
  4. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,268

    The37Kid
    Member

    ^^^^ Really scary thing is I PM'd Weasel to say it was an alternator problem. Bob
     
  5. Carter
    Joined: Mar 18, 2006
    Posts: 1,406

    Carter
    Member

    Weasel, that was the exact scenario I had come up with in my head as to what had happened.
    I believe a diode soldered into the alternator exciter wire would solve this problem as well.

    Sent from my DROID device using the TJJ mobile app
     
  6. boooooob
    Joined: Sep 14, 2012
    Posts: 38

    boooooob
    Member


    As said before do them both...........

    HTML:
    http://www.gigavac.com/pdf/BD9521.pdf
    Sorry posted this on the positive /negative pole thread by mistake. And by the way, why didn't you just cut the alternator, and/or fuel pump wires???????? Because electricity is MAGIC, I would say some really bad things now but this is not my site..I am here as a guest:)......it was a good story though. And why didn't you not have the alternator power out wired BEFORE the positive cutoff switch..........I am being nice , so please do the same....even though I am an FNG, it is really scary what people think they know, including ME:D

    boooooob
     
    Last edited: Mar 30, 2013
  7. willys1
    Joined: Oct 31, 2012
    Posts: 1,021

    willys1
    Member
    from South Ga

    Bootlegger is correct. either will do. your are disconnecting the battery from either side with the switch. it is the same as disconnecting the battery terminal...therefore no current flow. And you should not kill the car by the cutoff switch while running, generally speaking..as your alternator is still working, although most are not charging hard enough at idle to keep the car running very long. .everyone has an opinion and most are with experience on the subject...good and bad..
     
  8. You all have me scared of electricity now.

    I'm going to convert to a kickstart diesel with acetylene lighting. No more electricity for me!!!

    Cosmo
     
  9. 5window
    Joined: Jan 29, 2005
    Posts: 7,531

    5window
    Member

    Ha! Trick question. First of all,dry human beings are not good conductors of electricity. You'll need to be wet, preferably with salt water, for any real conduction. Second, dirt or concrete is not a good "ground". Hammer a metal rod into the earth, then disconnect the negative post of your battery (or the positive post if it's a positive grounded system, once again). Then connect a wire from something theoretically powered through your battery, and still connected to the positive/powered side, to your pole in the ground-big spark?. Do the same thing the other way around-no spark. You like sparks? Especially when you're upside down in a pool of fuel after some clown texting ran a stop sign on you? Then, switch the ground side of your battery. Simple, really, don't make it complex.
     
  10. 5window
    Joined: Jan 29, 2005
    Posts: 7,531

    5window
    Member

    Yes,either will serve to disconnect the battery from the system-if that is your goal. If stopping potential power flowing to the rest of your car through an accidental grounding, then you need to disconnect the powered side, not the ground side-you can create another ground, you can't create another power feed.
     
  11. Carter
    Joined: Mar 18, 2006
    Posts: 1,406

    Carter
    Member

    What do you mean by accidental grounding? Grounding to the earth?
    Not going to happen in a DC automotive electrical system.



    Sent from my DROID device using the TJJ mobile app
     
  12. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,268

    The37Kid
    Member

    Just bought my second electrical item, boots to go over the battery termanals. They should prevent shorts/grounding, + - contacts. RIGHT?
     
  13. Carter
    Joined: Mar 18, 2006
    Posts: 1,406

    Carter
    Member

    As long as they don't get damaged and remain intact, they will prevent anything shorting directly to your battery.

    Sent from my DROID device using the TJJ mobile app
     
  14. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,268

    The37Kid
    Member

    1/4 -1/2 inch plate battery box with a lid sound ok to you?
     
  15. Carter
    Joined: Mar 18, 2006
    Posts: 1,406

    Carter
    Member

    That may be overkill, but would work. As an added measure you could glue some rubber belting to the inside of the lid.

    Sent from my DROID device using the TJJ mobile app
     
  16. BootleggerMatt
    Joined: Aug 17, 2011
    Posts: 258

    BootleggerMatt
    Member

    I'm speechless.
     
  17. WOW I never thought this would go on for 107 posts. I thought it was a fairly straight forward question. Theories and opinions abound. I think I got what I was looking for. Could be either cable depending on what you are trying to accomplish.
     
  18. either post will work, enough said!
    in a dc system water won't create a ground that would effect anything. ever back a boat trailer in the water?
    your body will pass a small amount of voltage. we used to test mid 80's gm ignition modules by sticking a paper clip into distributor plug, hold the paper clip in one hand and touch the positive terminal with the other and see if the coil sparks.
    i feel gingerbread in the shape of a bunny is bread, not a cookie.
     
  19. Dude, I'm gonna' step out of my comfortable spot here and in'ta the eye this shit storm.....

    In my forty years'a workin' the line for various marques I seen a buncha' stupid mishaps that coulda' been prevented by disconnectin' the battery before some lazy flat-ratin' idiot let the smoke outta' the main harness.

    Let's face it, most of our rides ain't never gonna' see a sanctioned track 'less it's parked outside in the lot. For those who's rides do, the NHRA's hot side battery/alternator kill switch system has merit.

    I think the idea of a big ol' cut off switch with a lightning bolt decal on a outer rear panel near a trunk mounted battery sounds cool, but it ain't practical for my rusty ol' tub.

    Way back in the dark ages I was trained to remove the ground cable first, and I've always stuck with that method.

    As the years went by, I began to use a 10A circuit breaker with two leads attached to it that I'd hook up in series 'tween the ground terminal and the battery post when I disconnected so I wouldn't have'ta hear customers bitch, moan and generally whine about losin' radio presets n' such.

    On my car, I run a simple terminal mounted cut off on the ground terminal:

    http://www.jegs.com/i/Moroso/710/74103/10002/-1

    It ain't as sexy as a big lever but it kills the power so if I'm feelin' lazy, I don't let the smoke out.

    But this is only my opinion, and opinions are like assholes- everybody's got one.

    Do whatever floats your boat.
     

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