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  1. #1

    Disconnecting a battery the correct way?

    Why do so many vehicle manufactures recommend disconnecting the positive terminal first? I can not see any reason why it would matter. I would think it would be safer disconnecting the neg first as it would not matter if you were to touch the wrench to a ground. I have been disconnecting the neg side on one of my jet skis and my rectifier-regulator just took a dump, it could have been a coincidence.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by mikel1 View Post
    Why do so many vehicle manufactures recommend disconnecting the positive terminal first? I can not see any reason why it would matter. I would think it would be safer disconnecting the neg first as it would not matter if you were to touch the wrench to a ground. I have been disconnecting the neg side on one of my jet skis and my rectifier-regulator just took a dump, it could have been a coincidence.
    Where are you seeing recommendations to disconnect the positive terminal first?

    My understanding is that the long standing recommendation, and indeed the safer method, is to always disconnect the negative battery terminal first.

    Certainly that is the recommendation of Polaris Service Manuals.

    Quote Originally Posted by Polaris 1992-1998 Service Manual
    Always disconnect the black (negative) cable first.
    When reconnecting the battery cables, the positive cable gets connected first, and the negative cable gets connected last.

    The reason is, of course, that when disconnecting the first battery cable, a tool shorting between the engine itself and the tool will have no effect if the tool is removing the negative cable first. If the tool was removing the positive cable first, and it touched the engine, then a massive short and angry sparks would occur.

    When disconnecting and especially when reconnecting the battery cable, you want to avoid a 'bouncy' cable connection to the battery terminal. Touching and retouching the battery terminal in quick succession can create voltage spikes which can damage electronics. When reconnecting, have the battery post and the cable end all clean and ready, then use a firm hand to connect and hold the cable in place in one motion, firmly against the battery post. Then tighten the bolt to hold the cable down.

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    On my X45 and on My Pro 1200, there is a weatherpack connector on the positive wire that comes off of the battery cable and runs into the electric box. I always disconnect this plug and it kills all of the power to everything in the ski. Makes it a little safer on the electromics, especially the MFD if you should bounce the connection. I have seen the hours on an MFD reset to zero after bouncing a connection.

  4. #4
    Quote Originally Posted by K447 View Post
    Where are you seeing recommendations to disconnect the positive terminal first?

    My understanding is that the long standing recommendation, and indeed the safer method, is to always disconnect the negative battery terminal first.

    Certainly that is the recommendation of Polaris Service Manuals.



    When reconnecting the battery cables, the positive cable gets connected first, and the negative cable gets connected last.

    The reason is, of course, that when disconnecting the first battery cable, a tool shorting between the engine itself and the tool will have no effect if the tool is removing the negative cable first. If the tool was removing the positive cable first, and it touched the engine, then a massive short and angry sparks would occur.

    When disconnecting and especially when reconnecting the battery cable, you want to avoid a 'bouncy' cable connection to the battery terminal. Touching and retouching the battery terminal in quick succession can create voltage spikes which can damage electronics. When reconnecting, have the battery post and the cable end all clean and ready, then use a firm hand to connect and hold the cable in place in one motion, firmly against the battery post. Then tighten the bolt to hold the cable down.
    I agree with you 100%, but just today I was working on my Chev Silverado and the shop manual specifically said to disconnect the positive battery terminal I have seen this many times in the past, that is why I am asking.

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    David Drkvampire2001's Avatar
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    Quote Originally Posted by mikel1 View Post
    I agree with you 100%, but just today I was working on my Chev Silverado and the shop manual specifically said to disconnect the positive battery terminal I have seen this many times in the past, that is why I am asking.
    On a vehicle I could see why because if your neg cable comes in contact with any metal surface it effictively re powers the vehicle. So by removing the positive first you shrink that risk a lot. Now on the other hand removing the positive first does raise the chance of spark

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by mikel1 View Post
    ... just today I was working on my Chev Silverado and the shop manual specifically said to disconnect the positive battery terminal ...
    Is that a diesel vehicle, or has dual batteries?

    Care to post the exact words from that shop manual?

  7. #7
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    regardless of what any manual would tell me, always remove negative cable first.

    (unless you've got one of those rare brit motorcars that use a positive ground of course)

    That in simple terms is Best Practice

    if you've ever seen a wrench explode after coming across the positive terminal and a ground, you'll get the picture, hopefully with all of your fingers intact.

    Batteries are highly underrated as improvised explosive devices. doesn't take much to detonate one and really really really ruin your day.

    I'm sure if you sniffed around youtube, you can find somebody somewhere that melted a wrench for "show"

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Drkvampire2001 View Post
    On a vehicle I could see why because if your neg cable comes in contact with any metal surface it effectively re powers the vehicle.

    So by removing the positive first you shrink that risk a lot. Now on the other hand removing the positive first does raise the chance of spark
    Incorrect. The negative battery cable is already connected directly to the 'metal surfaces' of the vehicle because one end of that cable is directly bolted to the metal engine case or the vehicle body.

    The negative battery post is isolated as soon as the black battery cable is removed from that post, and therefore the now loose battery cable can touch anything else and it will have zero effect. The only live point is the actual negative post, which if you have removed the cable from that post, is now an open circuit.

    Remove the negative cable from the negative battery post, and instantly the entire electrical system is deenergized. Keep the negative battery post from re-touching anything and the electrical system remains deenergized and safe to work on.

  9. #9
    David Drkvampire2001's Avatar
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    Quote Originally Posted by K447 View Post
    Incorrect. The negative battery cable is already connected directly to the 'metal surfaces' of the vehicle because one end of that cable is directly bolted to the metal engine case or the vehicle body.

    The negative battery post is isolated as soon as the black battery cable is removed from that post, and therefore the now loose battery cable can touch anything else and it will have zero effect. The only live point is the actual negative post, which if you have removed the cable from that post, is now an open circuit.

    Remove the negative cable from the negative battery post, and instantly the entire electrical system is deenergized. Keep the negative battery post from re-touching anything and the electrical system remains deenergized and safe to work on.
    Woah my logic was skewed and completely reverssed. I feel like I was on drugs when I typed that holy cow. Keith to the rescue. Lol

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