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Thread: proper use of jumper cables

  1. #1
    Join Date
    Feb 2006
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    Default proper use of jumper cables

    I had to give a jump start to a neighbor with a dead battery. In the old days, I would have just hooked up the cables without giving much thought to the proper sequence of attachment -- that always worked. But now we are instructed to hook up in four steps: (1) positive terminal on live battery, (2) positive on dead battery, (3) negative (ground) on live battery, and (4) ground connection on the engine block on dead car.

    It was very difficult to find a bare bolt anywhere -- plastic obscured virtually the whole top of the engine. I attached the cable at the best place I could find. No dice. So I completed the job by using the ground terminal on the dead battery. The instructions had me thinking I was risking an explosion, but it worked.

    What would you have done?
    Last edited by aostling; 09-13-2018 at 12:39 PM.
    Allan Ostling

  2. #2
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    Aosling, I can relate so much plastic nowadays it's hard to find a negative connection !

    but - it's worth searching for yet I still use the batterys connections also - I think your procedure makes sense but im more concerned with the dis-connecting than the connecting and i'll tell you why, it's that the battery being charged gives off lots of explosive gasses - so after its been charging the last thing you want to do is disconnect any terminals around it, always disconnect at the car that's doing the charging esp. with todays electric fans and all even after the car that's being started starts there's no air flow to get rid of the explosive gasses, disconnect the negative at the vehicle that's doing the charging...

    something related to your post about not being able to find a negative,,, back in the day when cars had steel bumpers I went to rescue a Damsel in distress who was dead in the water with a low battery yet there was no way for me to get to the front of her vehicle with my cables as she was parked head into an area facing downhill and that i could not get too, no tow rope at the time - so what to do?

    I took my joined jumper cables and tore them apart making two separate ones, took the positive and connected it to one of the negatives --- I now had a jumper cable that reached my positive to her positive, then I just butted up my cars front bumper to her rear bumper,,, after a few minutes she went for a crank and it fired right up...

  3. #3
    Join Date
    Nov 2010
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    Red Deer, Alberta
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    Default

    Hey Allan,
    The reason for the final connection going to an engine or frame ground rather than the battery is in case a spark results which may ignite any stray hydrogen gas given off by the battery. This is most likely to occur when removing the cables. With the negative (ground) cable away from the battery, a spark is not near any of this gas reducing the danger of it igniting and causing a battery explosion. Once the vehicle is started, remove the dead vehicle ground cable first.
    Now, having said all that and having boosted and put battery chargers on literally hundreds and hundreds of vehicles over the years I have only actually seen one battery explode due to the above situation. That time we were having a particularly difficult time starting the vehicle and improper charging and other improper techniques used at the time caused the problem. The best way is as you outlined in your post and should be followed.
    What would I have done? Same as you ;-) Have a good day now that you’re mobile again!

  4. #4
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    Those cautions are there for a reason. It doesn't happen very often but an exploding lead acid battery is not a lot of fun. It's happened twice in my life.
    Once while jump starting a truck, as luck would have it the hood was partially closed and me off to the side and back. The connections had already been made and engaging the starter initiated the explosion. Sounded like a shotgun blast, acid and shrapnel everywhere!

    On my first experience I had one blow up in my face, I was covered in acid from the waist up. Fortunately a water tap less than eight feet away was my savior that day. The adrenaline was flowing that morning!!
    Both very rare occurrences but they do happen.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  5. #5
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    Willy You and Me both - as a young smart ass kid (who me? no really?) I used to temp fate all the time, I knew "why" the rules were in place just chose to find "clever" ways around them, one of my cheap thrills was actually disconnecting at the charged battery source while blowing directly on the terminal,,, well guess my aim was off a little - kaboom and my face was right in the line of fire, battery did not blow up cuz had the caps off for servicing - but shot acid everywhere including my eyes - at the old bossmans house/shop so ran to the house while spitting in my hand and rubbing it in my eyes, could feel the burning - get to the kitchen and the faucets taken by one of those portable dishwasher connections - - another delay trying to find the bathroom with burning eyes,,, found it and doused profusely - lucky I can still see today...

  6. #6
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    Yup, better to be lucky than good it seems.
    That and good lessons don't come easy.
    I think we are lucky to have survived our youthful exuberance and gung-ho attitudes.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  7. #7
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    Don't any of you folk have sealed/low maintenance batteries in your cars yet?

  8. #8
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    Quote Originally Posted by Mark Rand View Post
    Don't any of you folk have sealed/low maintenance batteries in your cars yet?
    Yes for the most part they are all sealed/low maintenance at this point. However that does not mean all in use are, thus the warning. Better to err on the side of caution especially when dealing with many users that may not be able to know how to discern the difference.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  9. #9
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    Quote Originally Posted by Mark Rand View Post
    Don't any of you folk have sealed/low maintenance batteries in your cars yet?
    Sealed batteries just make a bigger bang. I'm on the HAZMAT emergency response team for my workplace. Got called in on a weekend when a couple of SLAs exploded in a lab. Turned out to be a combination of factors; they were being charged from a lab power supply with adjustable output and someone bumped the knob up to about 17 volts and left for the weekend. The over-voltage caused them to gas and balloon outward. Eventually, the seals ruptured spewing acid everywhere and releasing a magnificent cloud of hydrogen sulfide gas - stinky, toxic and explosive. My favorite combination.

  10. #10
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    Here's another that learned the hard way. Left my battery on the charger overnight. Came out in the morning, Disconnected a terminal, and boom.

    Not a big boom - just enough to blow the top off the battery and generously sprinkle acid over my face. Yes - I knew the way to water with my eyes shut. No damage. The only nuisance was the stream of people coming to ask if I was OK.

    On a lighter note, once I was driving with a battery in the boot (trunk). I'd had the forethought to put one of those old plastic raincoats under the battery to protect the floor. Drove round a bend and heard the battery go over. I stopped, took the battery off the coat and thought I'd shake the coat out so the spilt acid didn't get on the floor. Look, when you shake something wet, you get a little wet. My scalp itched badly all the way home.
    Richard

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