getting shocked?

[crzrcrzy]

I get a light shock when touching the positive battery post and the boby of my 91 fj80. What gives? Do I have a ground missing? I recently installed 1/0 battery cables. The negative cable is grounded to the motor mount and the motor is grounded to the body. Should be a complete ground right? Or do i need the ground from the negative cable to the body?

 

[JohnR]

12v systems shouldn't be able to shock you through uncut dry skin. It should be grounded to the body as well.

 

[-Spike-]

You should have a separate body ground, yes.

 

[crzrcrzy]

So the ground from the motor to the firewall is not enough? I need a ground from the negative cable to the body. Correct?

 

[JohnR]

Correct. All vehicles have a ground directly from the negative terminal to the body. Then a large gauge cable from the negative terminal to the engine block, with several flat ribbon cable grounds from the engine block to the frame / body. But, the negative terminal to the body is VERY important.

 

[crzrcrzy]

Roger that. Thanks fellers
Adam

 

[-Spike-]

That being said, not sure why you're getting shocked, and another cable to the body should only make the shock worse, if anything. It may just be your body chemistry, maybe you're more conductive than most...? Is it a continuous shock when you are touching the positive terminal and the body, or a single spark, like static?

 

[Eicca]

Maybe he's an X-Man or something. THE MECHANIC.

 

[skintunes]

That is totally normal - may sometimes not be felt due to chemistry, humidity,arid conditions etc. Electrons are searching thru your body to ground- path of least resistance.... Why are you doing that any way???

 

[tirewater]

That is totally normal - may sometimes not be felt due to chemistry, humidity,arid conditions etc. Electrons are searching thru your body to ground- path of least resistance.... Why are you doing that any way???

Heh, yeah...why are you doing it?

I want nothing to do with the red post. In high school I changed my battery on my Chevette using bare metal channel locks. One handle fell out of my hand while tightening the battery post and touched the opposite post.

BANG! A blue flash and a bit of smoke. The result was a big chunk of the handle being melted.

Reality hits you hard bro.

 

[Ebag333]

Heh, yeah...why are you doing it?

I want nothing to do with the red post. In high school I changed my battery on my Chevette using bare metal channel locks. One handle fell out of my hand while tightening the battery post and touched the opposite post.

BANG! A blue flash and a bit of smoke. The result was a big chunk of the handle being melted.

Reality hits you hard bro.

12v really isn't all that dangerous, at least not at the amps we're dealing with. Virtually all deaths from 12v happen after the shock (E.G. someone falling and hitting their head). Even 120v doesn't kill that many people.

Now 220v is a different story.....



That being said, it's good to respect even 12v. Keep in mind that a couple 12v batteries can weld steel, so in the right set of circumstances you can do serious harm.

 

[tirewater]

12v really isn't all that dangerous, at least not at the amps we're dealing with. Virtually all deaths from 12v happen after the shock (E.G. someone falling and hitting their head). Even 120v doesn't kill that many people.

I think you're second sentence defeats your first sentence. If getting electrocuted causes a death either indirectly or directly, better to not get electrocuted.

Regardless, I know you mean at general auto fuse levels, the car's 12v doesn't to much harm. The body is not very conductive and 12v isn't quite enough voltage to get through you, in addition most fuses are in the 7.5amp-10amp range anyway.

The larger batteries that some are carrying are capable of putting 10k+ watts (say 850a x 12v). The 220v w/ 30amp circuit breaker hits 6600 watts (true wattage can get much higher because it takes time for the breaker to trip). The main difference is that 220v is *much* more likely to flow through your body. Also to be taken into account is whether the electricity is AC or DC....

 

[Ebag333]

I think you're second sentence defeats your first sentence. If getting electrocuted causes a death either indirectly or directly, better to not get electrocuted.

It's only a risk to those of us who need to stand on a ladder to wrench on our trucks.

 

[Eicca]

3 volts can kill just as easily as 30,000 if the amperage is high enough. Car batteries are more than up for the job...

 

[crzrcrzy]

Why are you doing that any way???

Ha! I was leaning over hooking something up on the new 2fe and thought i felt a light shock. So naturally i had to do it a few more times to verify that i really was getting shocked.

 

[JohnR]

It only takes about 100MA to kill you. Batteries can do several thousand for a split second.

BUT, 12v isn't enough voltage to cause current to flow through skin. That's why a BBQ ignitor run off a single AA battery can shock you enough to feel it, but a car battery doesn't (on clean, dry skin).

BBQ ignitors up the voltage to a few thousand, but with a few PICOamps of current.

 

[Ample]

A car battery can be dangerous.

I know of someone in an offroad club who was connecting up a car battery and somehow the spanner on one of the terminals accidentally touched his wedding ring. The ring turned so hot in a split second that it burned through his finger to the bone!

 

[Wagnerwerks]

A car battery can be dangerous.

I know of someone in an offroad club who was connecting up a car battery and somehow the spanner on one of the terminals accidentally touched his wedding ring. The ring turned so hot in a split second that it burned through his finger to the bone!

I know 2 people that fried fingers while working under the dash. Wedding rings.... As a youngster, I was tightening up a dual battery setup on a roadster and fried a wrench pretty bad. Great lesson...

 

[skintunes]

I know 2 people that fried fingers while working under the dash. Wedding rings.... As a youngster, I was tightening up a dual battery setup on a roadster and fried a wrench pretty bad. Great lesson...

don't get married.... invaluable lesson

 

[Eicca]

Ah, wedding rings. Guy I worked with at my old shop (looked just like Leonard Nimoy) literally vaporized his ring on a terminal post. Left a cool scar.