Working on live ckts

[busman]

If low DC voltages are really so dangerous, there should be thousands of dead stick welders all over the world.

 

[electrofelon]

If you guys don't know how easy it is to get shocked from a battery then you just don't have the experience. And It is just as easy to deliberately shock someone with 120v or 1v. If you don't believe that, that is just fine.

What kind of battery are you talking about? A series connected bank or just 12 volts? I've changed or moved about a trillion 12 volt batteries, lived and worked on off-grid 12 volt systems, never gotten a shock from 12 volts.

 

[petersonra]

It is hard but not impossible to harm yourself with a 12 Volt circuit.

For instance, if you had a cut that opened the skin, you would no longer have the skin protecting you. Skin tends to have a fairly high resistance. The tissue and blood under the skin does not.

 

[busman]

But you would need TWO cuts wouldn't you, one for entry and one for exit?

It is hard but not impossible to harm yourself with a 12 Volt circuit.

For instance, if you had a cut that opened the skin, you would no longer have the skin protecting you. Skin tends to have a fairly high resistance. The tissue and blood under the skin does not.

 

[petersonra]

But you would need TWO cuts wouldn't you, one for entry and one for exit?

not necessarily. the skin resistance would basically be half what it otherwise would be. and if the other point of contact was damp or bloody, the skin resistance there could be much lower than normal.

keep in mind that skin resistance can be anywhere from 1000 to 100000 ohms based mostly on how moist it is.

two points of contact at 1000 Ohms each and 12 Volts gives you a current of 12/2000 = 6 mA. You will feel that. if one of the points of contacts is a cut it will be closer to 12 mA and you will really feel that.

 

[ggunn]

If you guys don't know how easy it is to get shocked from a battery then you just don't have the experience. And It is just as easy to deliberately shock someone with 120v or 1v. If you don't believe that, that is just fine.

I am so very glad to hear that it is "just fine" that I don't believe you. Show me a single documented case of someone being shocked with a 1V battery. You can probably be shocked by a 6V battery if the contacts are close enough together that you can touch them both at the same time with your tongue; I'll give you that. That's how I check 9V alkaline batteries.

Many times I have simultaneously touched both poles of a 12V automotive battery with many hundred available amperes. I never felt a thing.

 

[Besoeker3]

I'm amazed that I have survived this long...................................even with 12V................

 

[jaggedben]

If you guys don't know how easy it is to get shocked from a battery then you just don't have the experience. And It is just as easy to deliberately shock someone with 120v or 1v. If you don't believe that, that is just fine.

Ok, I don't believe that.

(Man, all those times I grabbed a AAA from both ends. )

 

[rambojoe]

It is hard but not impossible to harm yourself with a 12 Volt circuit.

For instance, if you had a cut that opened the skin, you would no longer have the skin protecting you. Skin tends to have a fairly high resistance. The tissue and blood under the skin does not.

Perspiration. Ask a mechanic. Then we can get into the intentional ways like jumper cable jaws. It doesn't matter, it's just hard to tell if the other buddies here like debate club or are really that dumb. I think it's a bit of both. I have 2 plane tickets for the "prove it" kids.

 

[retirede]

I am so very glad to hear that it is "just fine" that I don't believe you. Show me a single documented case of someone being shocked with a 1V battery. You can probably be shocked by a 6V battery if the contacts are close enough together that you can touch them both at the same time with your tongue; I'll give you that. That's how I check 9V alkaline batteries.

Many times I have simultaneously touched both poles of a 12V automotive battery with many hundred available amperes. I never felt a thing.

I used to shock the snot out of kids in high school with a ‘D’ cell. Of course it was wired to an inductor and switch!

 

[Frank DuVal]

When on my back under a dashboard, sweating, and my forehead touching the steel, if my hand touches a +12 volt wire, I can feel it in my head enough to make me jump. Two dry hands on the car battery, nope.

Arc flash of a vehicle battery is bad when the spark at the terminals ignites the hydrogen/air mixture. Seen it too many times to say never! Taken employees to the emergency room because of it. You know, journeyman sits in truck that won't start, has apprentice wiggle battery connections while he turns key. Blam. Off to the ER after a quick rinse. Sometimes they just explode when trying to start. Lucky, the hood is usually closed then.

 

[electrofelon]

When on my back under a dashboard, sweating, and my forehead touching the steel, if my hand touches a +12 volt wire, I can feel it in my head enough to make me jump. Two dry hands on the car battery, nope.

Arc flash of a vehicle battery is bad when the spark at the terminals ignites the hydrogen/air mixture. Seen it too many times to say never! Taken employees to the emergency room because of it. You know, journeyman sits in truck that won't start, has apprentice wiggle battery connections while he turns key. Blam. Off to the ER after a quick rinse. Sometimes they just explode when trying to start. Lucky, the hood is usually closed then.

I have a hard time believing that and never ever seen or heard of that happening and I've messed with batteries a lot more than the average bear I'm sure. Between living off grid with batteries, all my equipment, all my poor connections I procrastinate fixing, and being too cheap to get batteries for everything so I'm always moving batteries around...... For one thing the battery only makes hydrogen when it's being charged,. Even Then I highly doubt you would get a high enough concentration to ignite.

 

[Little Bill]

I have a hard time believing that and never ever seen or heard of that happening and I've messed with batteries a lot more than the average bear I'm sure. Between living off grid with batteries, all my equipment, all my poor connections I procrastinate fixing, and being too cheap to get batteries for everything so I'm always moving batteries around...... For one thing the battery only makes hydrogen when it's being charged,. Even Then I highly doubt you would get a high enough concentration to ignite.

Wish I had taken a picture of what happened in my Dad's garage. He put a 12V battery on the battery charger and left it overnight. Next day he went out to the garage to disconnect the charger. What he found was the shell of the battery with the top blew off and parts of it stuck in the ceiling of the garage! Would have been bad if someone was standing over that battery, or even close to it, when it blew!!!

 

[electrofelon]

Wish I had taken a picture of what happened in my Dad's garage. He put a 12V battery on the battery charger and left it overnight. Next day he went out to the garage to disconnect the charger. What he found was the shell of the battery with the top blew off and parts of it stuck in the ceiling of the garage! Would have been bad if someone was standing over that battery, or even close to it, when it blew!!!

Souods like a sealed battery that had some sort of issue or charged at too high a rate.

 

[ggunn]

I have a hard time believing that and never ever seen or heard of that happening and I've messed with batteries a lot more than the average bear I'm sure. Between living off grid with batteries, all my equipment, all my poor connections I procrastinate fixing, and being too cheap to get batteries for everything so I'm always moving batteries around...... For one thing the battery only makes hydrogen when it's being charged,. Even Then I highly doubt you would get a high enough concentration to ignite.

Lead acid batteries do occasionally have explosions; my dad once had one blow the cover off while he was close to it. Luckily he had glasses on that kept the acid out of his eyes.

 

[Little Bill]

Souods like a sealed battery that had some sort of issue or charged at too high a rate.

Just a regular lead acid with caps. His old charger only had a choice of 6V or 12V, no timer or anything.

 

[LarryFine]

Generac gennies were known to blow up batteries.

 

[GoldDigger]

Perspiration. Ask a mechanic. Then we can get into the intentional ways like jumper cable jaws. It doesn't matter, it's just hard to tell if the other buddies here like debate club or are really that dumb. I think it's a bit of both. I have 2 plane tickets for the "prove it" kids.

Puncturing the skin with loose strands from a high conductor count, fine stranded, cable could take care of one or both ends too.

 

[RatherBeFishin]

If I "must" (separate discussion) connect a device while the circuit is hot, I also connect the hot conductor to its terminal first and the EGC last, especially with narrow-body 15a switches. Their screw terminals are particularly close to the metal yoke.

That way, I know where the hot is, I don't have to divide my attention, and I have control of it while connecting the rest of the wires. I don't risk getting shocked if the hot inadvertently touches the yoke because I always hold the yoke with my pliers.

I don't want a fault arcing in front of me even if I won't get a shock from it (which is itself debatable because half voltage (or more) could theoretically appear at the fault point).

@LarryFine

I guess holding the device with the pliers is a good idea, more so if the ground is hooked up and you’re landing the hot but can’t hurt. If the ground isn’t hooked up you could touch that yoke with the hot all day and not get shocked but who knows the other variables like what you’re standing on.

Question for you, if you did land the ground first and we’re holding the grounded yoke with one hand and had the hot wire held by the insulation firmly and that hot hit the yoke, the ckt should trip but could you also get shocked by holding the yoke with one hand at that same moment?

 

[jaggedben]

@LarryFine

...

Question for you, if you did land the ground first and we’re holding the grounded yoke with one hand and had the hot wire held by the insulation firmly and that hot hit the yoke, the ckt should trip

You'll get an arc. There's no meaningful likelihood that the breaker will trip.

but could you also get shocked by holding the yoke with one hand at that same moment?

No. You haven't described the body touching two points at different potential.