You're right... once the positive is disconnected it's not hot anymore.
But on a setup with multiple batteries like mine, it's somewhat risky
still to have one pos terminal hanging free. But your answer is right
on.

Jim

On Sep 21, 2004, at 8:46 PM, Bruce Nadig wrote:

>
> The answer below is close to the truth, but not right on.
>
> True, the body of the vehicle is negative. Chances are that any tool
> (such as a socket or box-end wrench) you would use to loosen the
> battery terminal would be metal. If that metal tool was being used to
> disconnect the positive terminal first and it hit the body while doing
> so, things would get real exciting real quick. I have heard stories of
> mechanics even having their rings (ie. wedding rings) getting "welded"
> between a positive and negative connection.
>
> If you take your metal tool and disconnect the negative side first,
> you won't have a problem if your wrench touches the body because the
> body is just an extension of the negative side of the electrical
> system. If your negative is still connected and you are attempting to
> disconnect the positive terminal and that same tool contacts the
> negatively charged body, at a minimum, you will get a large spark.
> Being so close to the battery, that spark could very well ignite any
> hydrogen gas that has been discharged from the battery (that is why
> you don't connect your negative cable on your jumper cables to the
> battery).
>
> What is stated below isn't quite true. Once the positive cable is
> disconnected from the battery terminal it no longer has a charge in
> it, so it doesn't make any difference if it hits the negatively
> charged body (which is no longer negatively charged, by the way,
> because there is no longer a complete electrical circuit). You could,
> in fact, safely put that positive terminal to the negative terminal to
> the battery and nothing would happen so long as there is nothing
> connected to the positive terminal of the battery.
>
> Make sense?
>
> Be Safe.
>
> Another electrical tip: When giving someone a jump start, make sure
> that the vehicles that are involved in the jumping process are not
> touching in any way.
>
> Cheers,
> Bruce
> motorbruce
> motorbruce@hotmail.com
>
>
>
>> From: Jim Felder <felder@KNOLOGY.NET>
>> Reply-To: Jim Felder <felder@KNOLOGY.NET>
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Re: Q: Battery Disconnect Sequence?
>> Date: Tue, 21 Sep 2004 19:56:31 -0500
>>
>> It's not the sequence.
>>
>> On any car but old english ones, the negative is the ground, and it's
>> strapped to the car frame somewhere. So you could say that everything
>> on the car is "negative" that is connected to the frame by even a
>> fastener. If you take the positive cable loose, it stands every chance
>> of hitting one of these negative frame or body members (engine too,
>> everything) and you'll get a big hot spark in the best-case scenario.
>>
>> Letting the negative cable hit anything but the positive terminal, and
>> nothing will happen.
>>
>> Jim
>>
>> On Sep 21, 2004, at 8:46 PM, Jack wrote:
>>
>>> Ok, I need help.
>>>
>>> In several manuals, including a Ford Owner's manual (forgive me) and
>>> a
>>> Haynes repair manual, I've noticed that they specify that the
>>> negative
>>> battery cable must be removed first when disconnecting the battery.
>>> Why???
>>>
>>> What possible difference can it make which terminal is disconnected
>>> first???
>>>  When I first ran across this, I ignored it as a harmless error by
>>> someone
>>> who didn't understand electrics, but now I find it in "professional"
>>> references.
>>>
>>> Help!  What am I missing?
>>>
>>> //Jack
>>>
>
>
>