[Amps] HV SAFETY QUESTION

[Jim Isbell]

On a 19" rack full of batteries (floor to ceiling) that had only a 
potential across the terminals of  12Vdc, one of the technicians decided 
to replace a screw in a barrier strip that was missing.  Most of us 
realize there is a reason that the thread on those screws is NOT 
standard.  It is so that you dont get the wrong screw in the hole!! 
 This guy found a screw (naturally it was too long , not too short) and 
even though the thread was wrong he managed to screw it in with a big 
screw driver.  When it hit bottom the 12V was shorted to the chassis 
with lots of AMPS.  I made that sickening hum like a huge transformer 
firing up and from the front of the rack I could see a red glow all 
around the rack.  The arc continued until the metal was eaten away far 
enough to break the arc, about 1/2" in all directions.  When I went back 
the guy was sitting on the floor leaning against the wall with his eyes 
as big as saucers and just staring with his mouth wide open.  Only his 
pride was hurt.

k7fm wrote:

>Hi Jim:
>
>It does not even take high voltage to put on a show.  I used to have 1700
>amp hour batteries for my wind generator (2 volt cells).
>
>One day someone came and laid a large 14" crescent wrench across the
>terminals.  The crescent wrench was reduced to little balls of metal.  I was
>not there at the time but understand it was quite a show.  I then decided to
>lock the door to the battery room.  I did not realize that the case on one
>cell cracked and 5 gallons of battery acid spilled on the concrete floor and
>turned the concrete to mush.
>
>73,  Colin  K7FM
>
>
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