Higher voltage for vehicles?

Joe

Auto mfgrs have been looking at 42/48 volts sytems for quite awhile but can not agree on a common system. The battery mfgs of the world are ready to make them, once they can all agree on one way to go. Most are looking at having a 12 volt starting system, thus not having to re-invent that, but then transfer to a 36/42/48 (thus the disagreement) operating system to run all the toys that buyers demand these days.

The charger company I work for has many prototypes working, and waiting for some kind of stardard to be developed.

IMHO the move to higher voltages is just a way to make cheaper cars. ie smaller gauge wires, etc. But you the consumer will pay much more for each replacement battery. And with more cells in the battery the odds of the battery going bad increase. They save we pay as usual.

Current is what kills. AMPS. Get that through your head!

As long as there is enough voltage to overcome the resistance, current will flow, if enough does, you die.

For example, many of us who actually have dealt with electricity have been exposed to 25KV - 50KV with nothing more than a sharp sting. Of course, it was milliamp current. On the other hand, you can easily kill a human being with 12V but in the interest of keeping some kid like you from trying it out, I'm not going to describe it further.

In general, higher voltages are more dangerous than lower voltages. If this were not true, then you would never hear of an electrocuted lineman, but every day you'd hear about someone who was electrocuted while jump-starting their car.

Yes, it is true that you need to exceed a certain current threshold to cause injury or death, but the probability of that increases with voltage.

Now the experience that most of us have with high voltages is the secondary side of an automotive ignition system. Although the voltage is in the tens of thousands of volts, the coil is not capable of sourcing enough current to cause harm. Also, the brief pulse has relatively little energy and, because of its high frequency components, the current tends to travel through the outer surface of your skin instead of going through your heart.

The bottom line is that your skin is an insulator, but it's only good to about 50 volts. Above that, it becomes a pretty good conductor.

Jump starting a 12V car cannot possibly be dangerous as 12V is normally not enough to penetrate skin as you pointed out.

The 7.5KV lines or whatever they are in your area certain have enough voltage to penetrate skin, but if they delivered milliamps you would feel little or no sensation. It's the high amperage that burns/kills linemen.

I do agree that certain combinations of voltage/amps affect different parts of the body differently. That's why getting tangled up with a household 220V line at 20 amps is remarkably effective in stopping the human heart.

Not trying to pick a fight, i just know I've shorted a 12v car battery from one hand to the other without suffering too much of an effect.

Darren

Effects of Electrical Current* on the Body 3 Current Reaction 1 milliamp Just a faint tingle. 5 milliamps Slight shock felt. Disturbing, but not painful. Most people can "let go." However, strong involuntary movements can cause injuries. 6-25 milliamps (women)�
9-30 milliamps (men) Painful shock. Muscular control is lost. This is the range where "freezing currents" start. It may not be possible to "let go." 50-150 milliamps Extremely painful shock, respiratory arrest (breathing stops), severe muscle contractions. Flexor muscles may cause holding on; extensor muscles may cause intense pushing away. Death is possible. 1,000-4,300 milliamps (1-4.3 amps) Ventricular fibrillation (heart pumping action not rhythmic) occurs. Muscles contract; nerve damage occurs. Death is likely. 10,000 milliamps (10 amps) Cardiac arrest and severe burns occur. Death is probable. 15,000 milliamps (15 amps) Lowest overcurrent at which a typical fuse or circuit breaker opens a circuit!

*Effects are for voltages less than about 600 volts. Higher voltages also cause severe burns.
�Differences in muscle, skin thickness, surface moisture and fat content affect the severity of shock.

If one were to take a fresh 9V battery and place the terminals on his tongue...

That's all I'm going to say.

Please excuse my jumping in here where I should keep my nose out of the bickering between you two guys.

I believe everyone enjoys a topic with a good debate of "facts" but when it comes down to name calling or personal attacks, people will loose interest real quick.

That being said, I enjoy reading both your inputs on this forum without the personal attacks.

Just my thoughts!

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I was always taught that 50v was the NEC cut off between low and high voltage considerations. I never looked it up in the code book so I agree Glen's reading of the NEC of 48v and also the posting of the human body resistance numbers as I've never knew of the exact numbers (good snag).

"Most" people can deal with high DC voltage, low current, well without too many side effects. DC current travels one way, from negitive to positive (non-electronic circuits).

However AC voltage travels both ways or alternates between hot and neutral and is more dangerous to "most" people than DC as it doubles the current absorbed by the body.

I think most of us working on engines have at one time grabed that spark plug wire at the wrong time and got hit with 10k vDC shock without any permanate harm. But beware as thats not always the case.

I was working with a man one time that was using a chain for a safety lanyard (many moons ago when legal) welding "I" beams when he got hung up with the electrode on the chain with his bare leg touching the "I" beam. That was about 18vdc and 180amps and I had to turn the welding machine off to stop his muscle contractions. He spent a few days in the hospital.

The "majority" of the people touching a 115vac 15amp circuit will be seriously injured or die because the alternating high current contracts the muscles to where you can't let go.

Most sparky's will tell you that they would rather be hit by 230vac plus voltage as that usually will burn off the offending body part and give you a chance to live.

I was working on a AC unit one time wearing a new SS watch I got for fathers day and hit a 340vac capacitor with the SS band. Lucky it burnt the band off the wire and only left me with a serious wrist burn.

Another time I stuck my welding electrode to the top of my wedding band.

As stated, take off any metal personal items from your body when working with any type electricity.

T_Bone

Bared 'bout 6 inches of copper and frayed it all out and fed it up between seat and back and laid it on the driver's seat and waited...

Hee, hee, pretty mean and all, but man did he squall like a girl when he hit that key!!!

Coulda prolly kilt him, but I'm gigglin' right now, 24 years later just thinkin' about it! Cheez 'n rice, that was funny.

Course that's the same buddy who's boots got soaked (just the steel toes, mind you) with lighter fluid while he slept, hung over, in a chair. Took about a minute to burn off...and that woke him up!