electrocution by car battery

Hi...

Just a question running through my mind. I know that a 12volt car
battery can't electrocute you.

What if i pass it through a step up dc converter to let say 110v for
the or 240v . Would the car battery now electrocute me if i were to
touch the neg and pos since the power supplied by the battery is almost
equivalent to the power supplied by the house electrical power source?

 

[PeteS]

Fibrillation (which is what kills you) is perfectly possible with a 12V
battery in the 'right' conditions.

What it takes is 100mA through the heart (an acquaintance of mine got
killed this way doing a charging check on the 28VDC system in a
helicopter many years ago)

As your effective skin resistance varies, it will depend on your
effective resistance being about 80-100 ohms, and the current going
from one set of fingers to the other (so the current path is through
the heart area).

Cheers

PeteS

 

what i meant was after stepping up the battery to a very high voltage
such as 110 or 240 volt... would it kill you if you touch the terminal
at the point after stepping it up? cuz from my guess it should right?
because the voltage is now high enough to penetrate the skin and the
current is also quite big.

 

[Bill Bowden]

would it kill you if you touch the terminal
at the point after stepping it up?
cuz from my guess it should right?

120 or 240 is not very high. You would get shocked, but probably
wouldn't die.

An electric chair that kills people operates on 2000 volts and can be
powered from a 12 volt car battery.

-Bill

 

[Bill Bowden]

120 or 240 is not very high. You would get shocked, but probably
wouldn't die.

What news source are you reading? People are electrocuted
every year from those "not very high" voltages.

I'm not reading a news source, just stating experience.
I've been shocked many times from line voltages with
no ill effects. Once, I was shocked by 10KV from
an aviation radar system, and it threw me across the room,
but I got up and went back to work.

120VAC is low voltage. Why do you think it's used instead
of 880 or higher, which would be much more efficient?

-Bill

 

i thought it's the current that kills not the voltage. the voltage is
just to get past the skin resistance to your heart. I read somewhere if
the current at about 0.030 amp would even stop your heart.

Bill Bowden wrote:

120 or 240 is not very high. You would get shocked, but probably
wouldn't die.

What news source are you reading? People are electrocuted
every year from those "not very high" voltages.

I'm not reading a news source, just stating experience.
I've been shocked many times from line voltages with
no ill effects. Once, I was shocked by 10KV from
an aviation radar system, and it threw me across the room,
but I got up and went back to work.

120VAC is low voltage. Why do you think it's used instead
of 880 or higher, which would be much more efficient?

-Bill

 

[Bill Bowden]

i thought it's the current that kills not the voltage.
the voltage is just to get past the skin resistance to
your heart. I read somewhere if the current at about 0.030 amp
would even stop your heart.

No, it's the power that kills, which is the
voltage squared divided by the resistance.

So, if your skin resistance is a Megohm,
you only get 120^2/1 Meg = 14 milliwatts which is not much.

But, if your hands are wet and the skin resistance is only 50K or so,
you get E^2/R =120^2/50K = 288 milliwatts, which might be dangerous.

-Bill

 

[Don Klipstein]

In article <1kbp911o7sf0bgf1v4jjdstaltfm8gn80q@4ax.com>, John Fields wrote:
(in part)

Using a Transco T1512, which is a 15kV 30mA NST, like this:


Iout-
120VAC>----+ +---------+ <-----+
)||( | |
)|| >-GND [R] Eout
)||( | |
120VAC>----+ +---------+ <-----+

I get the following data:

R Eout Iout
M kV pk mA RMS
-----+-------+--------
0.00 0.000 17.3
0.05 0.662 17.3
0.09 1.647 17.1
0.13 2.586 16.8
0.17 3.456 16.3
0.21 4.270 15.9
0.25 5.02 15.5
0.29 5.744 15.1
0.33 6.37 14.7
0.37 6.971 14.3
0.41 7.511 13.8

2.0 10.0 6.6
4.0 10.8 5.5
5.0 11.0 5.3
10.0 11.37 5.2
20.0 11.55 5.1

INF 15.0 0.0

Which shows there's no voltage regulation at all, but only a 3.5mA
change in current for a 7500V change in voltage across the load from
410kohms to a dead short.

The reason the short-circuit current is 17.3 mA instead of 30 is
because I loaded the entire secondary, and it's wired so you can only
get 15mA or so that way. If you take current from either end of the
secondary to the center tap you can get 15mA out of each half of the
secondary for a total of about 30mA.

This is much less current than I have found from a few neon sign
transformers and "oil burner" transformers. In my experience, the
short-circuit current using the entire secondary is close to the "label"
current or slightly higher, and with a load whose impedance is the ratio
of rated voltage to rated current I find voltage and current typically
around 60-66% of the "label" values.

- Don Klipstein (don@misty.com)

 

John Fields wrote:

On Mon, 30 May 2005 18:39:58 -0400, John Popelish <jpopelish@rica.net
wrote:

It can't, since it's designed to saturate at 30mA, but looking at its
load line it'll put out, say, 15kV at 0A into an open, and 0V at 30mA
into a dead short.

That means that with an initial 500kohm human load across it its
output voltage will drop to 7500VRMS and it'll be forcing 15mA through
the load, and the load will be dissipating about 113 watts. OUCH!!!

You may be right, but that is not what I understand to be the case. I
thought they are rated for normal load current over the voltage range
expected when driving a gas tube. And that they have a very nonlinear
current limit, much like Sola ferro resonant constant voltage
transformers. Those hold specified voltage regulation at rated
current but the current increases only to about double rated under a
short circuit. I don't think most neon sign transformers are just a
tightly coupled step up transformer in series with a big resistor.

---
AIUI, they're designed to be ballasts. That is, to start off with a
high enough voltage to strike the arc through the tube and then to
provide the proper current (30 or 60 mA) to run the tube when the gas
ionizes and provides a more or less constant low-resistance load
through the plasma.

Using a Transco T1512, which is a 15kV 30mA NST, like this:


Iout-
120VAC>----+ +---------+ <-----+
)||( | |
)|| >-GND [R] Eout
)||( | |
120VAC>----+ +---------+ <-----+

I get the following data:

R Eout Iout
M kV pk mA RMS
-----+-------+--------
0.00 0.000 17.3
0.05 0.662 17.3
0.09 1.647 17.1
0.13 2.586 16.8
0.17 3.456 16.3
0.21 4.270 15.9
0.25 5.02 15.5
0.29 5.744 15.1
0.33 6.37 14.7
0.37 6.971 14.3
0.41 7.511 13.8

2.0 10.0 6.6
4.0 10.8 5.5
5.0 11.0 5.3
10.0 11.37 5.2
20.0 11.55 5.1

INF 15.0 0.0

Which shows there's no voltage regulation at all, but only a 3.5mA
change in current for a 7500V change in voltage across the load from
410kohms to a dead short.

The reason the short-circuit current is 17.3 mA instead of 30 is
because I loaded the entire secondary, and it's wired so you can only
get 15mA or so that way. If you take current from either end of the
secondary to the center tap you can get 15mA out of each half of the
secondary for a total of about 30mA.

Facts are so much better than assumptions. Thanks for going to this
trouble for all of us. I dug a bit deeper, and my assumptions fell
through. I was thinking of the effect of the resonant circuit in a
ferroresonant transformer, and apparently, neon sign transformers have
only leakage inductance (more like the character of a microwave oven
transformer or welder), which would agree well with your measurements.
But I wonder how they get it to act as nonlinear as it does. It seems
strange that the short circuit current is only about 1.25 times as high
as the current that pulls the output voltage down by half. That surely
looks like an attempt at current regulation. On a graph of this data,
there is a bit of a kink.

 

John Fields wrote:
(snip)

There's another problem I'm trying to solve, though, and that's why
the output current is so low. I had thought that 15mA out of each
secondary to the center tap would result in 30mA total, but that's not
right. I called the manufacturer and their tech guy said that I ought
to get 30mA RMS out of the entire shorted secondary, just like Don
said. Well, he didn't say RMS, but...

The strange part is I've got a 9kV and a 15kV transformer, and I get
the same short circuit current out of both of them, making several
measurements with different meters.

I've got a friend who owns a sign shop, so I guess the next thing I'll
do is take a meter over there and see what a known good transformer
puts out.

Excellent. I love experimental science.

--
John Popelish

 

[Bill Bowden]

Your experience notwithstanding, people die from 110 vac.
You're healthy and lucky. Not everybody is.

Actually, I'm not healthy, but I am lucky. I have coranary heart
disease and luckily had a triple bypass operation last year that
brought me back to normal. I had angina pains when walking uphill, so I
went to a cardiologist, who gave me a treadmill test, and then told me
to go to the hospital. I was lucky again to have insurance that paid
$85,000 for the angiogram and surgery. Otherwise, I would be bankrupt
today.

But I feel pretty good now. I can walk uphill for long distances and
climb 4 flights of stairs with no pain.

Haven't tried the 120VAC shock test yet, but I'm really more afraid of
falling down than getting shocked.

Last month, I fell down and hit my head on a open tool box and needed 5
stitches. I would have much prefered being shocked from 120VAC than
smashing my head on a open tool box.

-Bill