Curious about the negative battery cable

wild70stang · Jul 9, 2008

So why is it that when ever your working on an electrical component that you only remove the negative cable; why must the positive cable stay on? I do know the hole process about the negative cable is first off and last on, but I was just curious.

coolblue65 · Jul 9, 2008

It really doesn't matter which one you disconnect, the idea is to cut the power.

65kcode · Jul 9, 2008

coolblue65 said:
It really doesn't matter which one you disconnect, the idea is to cut the power.

By taking off the negative first, it really limits the chance of any sparks, beause you have taken the grounding out of it. If the positive is taken off first, it's still grounded and will spark on the terminal.

Average person in the shop, not really going to make a huge deal. BUT if it's involved in an accident (MVA) where fuel is possibly on the ground, puddled in the engine compartment, etc. it can be very dangerous.

Kevin

coolblue65 · Jul 9, 2008

not saying your wrong, but I have seen plenty of sparks either way.

For the record I disconnect the positive first 99% of the time.

gtss · Jul 9, 2008

not saying either of you are wrong, but the idea is to minimize the chance of sparks causing a problem. not so much do to fuel in the area, but as a battery is being charged it releases gasses, those gasses are explosive the idea is to reduce the chance of explosion.

if you have ever seen the results a battery explosion make, it really is not pretty

gtss

p.s. if you are disconnecting the positive first you also have the posibility of shorting the wrench to ground where as once the negative is off... no problem

STSFCTN67 · Jul 9, 2008

This is why I take the neg terminal off first.

Have you ever welded a wrench to your radiator support loosening or tigtening the positive battery terminal??

This happens when you take a wrench to tighten the terminal and you touch the radiator support and it will ground out and scare the hell out of you and if you do not pull it away fast enough you will weld the two together.

So to answer the question take the neg off first and the last to put on.

wild70stang · Jul 10, 2008

lol guys. Everyone overshot my question. I was merely asking does it matter if you disconnect one terminal or both. When ever I did a Electrical job (alarm, ignition, etc) I always heard that most people just remove the negative. I usually disconnect both cables just for saving my ass in case of some freak accident (which happened and cost me $600). I also wasnt sure if disconnecting both for small jobs shortened the life of the battery for some odd reason, I ask that because a mechanic put in an interstate battery (long story I never like the brand) and it crapped out after 3 years (now I have a sears Gold class).

65kcode · Jul 10, 2008

We're all just over achievers.

Kevin

carefact0rzero · Jul 10, 2008

FYI, if you are going to take the positive off first, don't wear a watch with a metal band on it that was a fun one there...

D.Hearne · Jul 11, 2008

gtss said:
not saying either of you are wrong, but the idea is to minimize the chance of sparks causing a problem. not so much do to fuel in the area, but as a battery is being charged it releases gasses, those gasses are explosive the idea is to reduce the chance of explosion.

And these gases are what people are making now in the ever more popular "Browns gas" converters they're installing in their cars and trucks to improve fuel mileage. Most batteries now are sealed, so there's little chance of hydrogen gas release in the engine compartment. I'm with most, if and when i disconnect the battery, I don't have a preference on which terminal comes off first.

Tim65GT · Jul 11, 2008

wild70stang
lol guys. Everyone overshot my question. I was merely asking does it matter if you disconnect one terminal or both. When ever I did a Electrical job (alarm, ignition, etc) I always heard that most people just remove the negative. I usually disconnect both cables just for saving my ass in case of some freak accident (which happened and cost me $600). I also wasnt sure if disconnecting both for small jobs shortened the life of the battery for some odd reason, I ask that because a mechanic put in an interstate battery (long story I never like the brand) and it crapped out after 3 years (now I have a sears Gold class).

No, it does not matter. Disconnecting just the neg bat terminal is fine. You cannot complete a potential short circuit back to the battery while removing a component.

Removing the pos in addition to the neg doesn't hurt, other than the slight wear and tear on the terminal.

ForceFed70 · Jul 11, 2008

coolblue65 said:
not saying your wrong, but I have seen plenty of sparks either way.

For the record I disconnect the positive first 99% of the time.

Yes, he's wrong. There is the same amount of sparks either way.

As already mentioned, the negative terminal is reccomended as there is a much lower chance of accidently shorting out the battery with a wrench, watch strap, etc...

yeloxr7 · Jul 11, 2008

My rule: take off negative only if working on something electrical in the car, take off both if you need to remove or replace the battery.

Curious about the negative battery cable

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