Subject: [NEXTEL-1] Looking for HIGH DC amperage...REALLY high

From: "Todd Ellis" <[email-masked]>
Date: Mon, 3 Mar 2003 15:41:21 -0500

Here's a different question, maybe someone from the list will have an idea.

I'm looking to find something/someone that can simulate an accident.  I need
to provide a LOT of amperage at low voltage to simulate a particular vehicle
fire that involved three batteries in parallel - 12 VDC.  A 6-gauge copper
wire was supposedly designed by one entity to act as a fuseable link.  Yeah,
right.  

In order to do that, I need to come up with a way to dump approximately
2,000 Amps at 12 VDC for a period of 15-20 seconds.  If the test fails
(which we predict it will) and the copper wire itself melts/burns up, then
we will want to switch down to a lower amperage until we know how much
minimum current is needed to blow this "fusable link".  

Sure, we could use a battery bank and short it out, but measuring 2,000 Amps
in a test condition to verify the breakdown point of this cable (assuming it
actually breaks down) is not as simple.  

If anyone has any credible ideas, let me know.  I'm sure this one will have
a lot of other suggestions, LOL.

Todd Ellis

Booth & Associates, Inc.

Raleigh, North Carolina 

(919) 851-8770

[email-masked]

---

From: Jack Daniel <[email-masked]>
Date: Mon, 03 Mar 2003 15:49:09 -0800

Todd,

I thought no one even cared about the 'fusing' ratings of conductors
mucb any more.  It used to be common practice to use short lengths of
wires as fuses on board ships and we kept a stock pof various gauges and
a chart to repair foreign made shipboard radars, etc. By the way, it
works great!

But keep in mind these were always short (1 to 4 inch) lengths of
uninsulated wires located where the small amount of molten metal would
not start a fire. Otherwide they need to be housed in flame proof
material. These were NEVER long runs or jacketed wires becuase you could
not predict where the 'burn' would occur. 

Anyway, here's what my Reference Data for Radio Engineers say;

Formula: Fusing current (melts due to its own resistance) = I = K *
diameter (in) to the 3/2 power.

6 AWG Gauge wire. O.D. = 0.1660 inches.
Copper (K = 10244) = 668 amps
Aluminium (K = 7585) = 495 amps
Iron (K=3148) = 205 amps

For a good discussion (but at lower currents) check out:
http://www.ultracad.com/fusing.pdf

Hope this helps.
Jack Daniel
====================================

Todd Ellis wrote:
> 
> Here?s a different question, maybe someone from the list will have an
> idea?
> 
> 
> 
> I?m looking to find something/someone that can simulate an accident.
> I need to provide a LOT of amperage at low voltage to simulate a
> particular vehicle fire that involved three batteries in parallel ? 12
> VDC.  A 6-gauge copper wire was supposedly designed by one entity to
> act as a fuseable link.  Yeah, right.
> 
> 
> 
> In order to do that, I need to come up with a way to dump
> approximately 2,000 Amps at 12 VDC for a period of 15-20 seconds.  If
> the test fails (which we predict it will) and the copper wire itself
> melts/burns up, then we will want to switch down to a lower amperage
> until we know how much minimum current is needed to blow this ?fusable
> link?.
> 
> 
> 
> Sure, we could use a battery bank and short it out, but measuring
> 2,000 Amps in a test condition to verify the breakdown point of this
> cable (assuming it actually breaks down) is not as simple.
> 
> 
> 
> If anyone has any credible ideas, let me know.  I?m sure this one will
> have a lot of other suggestions, LOL.
> 
> 
> 
> Todd Ellis
> 
> Booth & Associates, Inc.
> 
> Raleigh, North Carolina
> 
> (919) 851-8770
> 
> [email-masked]
> 
> 
> 
> 
> 
> 
> 
>                    Yahoo! Groups Sponsor
>                        ADVERTISEMENT
> 
> 
> 
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

---

From: "Todd Ellis" <[email-masked]>
Date: Mon, 3 Mar 2003 21:47:48 -0500

Jack:

It sure does help!  Our guys are much more versed at much higher voltages,
not the low voltages like you would find in a commercial long-haul truck.

I believe this run, used as a fuse, is about a foot long.  The DC line
between the engine and the battery bank with double naught wire is a
whopping 109 inches.  Nothing was flameproof in this situation, and in fact,
after a minor accident, the resulting fire lit the diesel fuel, and the
truck and its driver burned up.  The battery bank was good to 2,000 amps
which would represent a dead short across the three batteries.  The question
is whether the 6 AWG cable was truly a "fusable link" in this case.

Folks, this can happen.watch how you install your radios in commercial
trucks.  We have a client who has had multiple mobile radio problems, all
attributable to the local shop cutting off the power from the battery, then
cutting off the connector at the cab and splicing in the new cable.  Take
the time to de-install old DC cables and grounding hardware when you are
installing a new radio.  Your client will appreciate it, believe me.

Todd Ellis

-----Original Message-----
From: Jack Daniel [mailto:[email-masked]] 
Sent: Monday, March 03, 2003 6:49 PM
To: [email-masked]
Subject: Re: [NEXTEL-1] Looking for HIGH DC amperage...REALLY high

Todd,

Hope this helps.
Jack Daniel

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---

From: Rick Parrish <[email-masked]>
Date: Mon, 03 Mar 2003 18:52:16 -0600

Todd Ellis wrote:

> Sure, we could use a battery bank and short it out,
>
In high school, we called this an "arc welder".

-rick

---

From: "Rik Rasmussen" <[email-masked]>
Date: Mon, 3 Mar 2003 20:40:04 -0500

Does Underwriters Labs in RTP have the capability?

==========================================
Henrik "Rik" Rasmussen
Editor: Two Way Radio Directory:
The Two Way Radio Directory has links to hundreds of industry related web
pages.
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  -----Original Message-----
  From: Todd Ellis [mailto:[email-masked]]
  Sent: Monday, March 03, 2003 3:41 PM
  To: NEXTEL-1@yahoogroups. com
  Subject: [NEXTEL-1] Looking for HIGH DC amperage...REALLY high

  Here's a different question, maybe someone from the list will have an
idea.

  I'm looking to find something/someone that can simulate an accident.  I
need to provide a LOT of amperage at low voltage to simulate a particular
vehicle fire that involved three batteries in parallel - 12 VDC.  A 6-gauge
copper wire was supposedly designed by one entity to act as a fuseable link.
Yeah, right.

  Sure, we could use a battery bank and short it out, but measuring 2,000
Amps in a test condition to verify the breakdown point of this cable
(assuming it actually breaks down) is not as simple.

  If anyone has any credible ideas, let me know.  I'm sure this one will
have a lot of other suggestions, LOL.

  Todd Ellis

  Booth & Associates, Inc.

  Raleigh, North Carolina

  (919) 851-8770

  [email-masked]

        Yahoo! Groups Sponsor
              ADVERTISEMENT

---

From: Jack Daniel <[email-masked]>
Date: Tue, 04 Mar 2003 07:37:12 -0800

Todd,

When you are considering fusing currents (I/R loss heating), voltage is
not part of the calculation. Voltage needs to be considered mainly for
insulation breakdown and arc paths, or in extremely high voltages and
with AC voltages, conductor surface current migration.

In the situation you are investigating, the 6 gauge fusing link should
have acted as fuse, BUT good installation practice says;
(1) the fuse link should be as close to the battery as possible.
(2) The high temperature that melts the 6 gauge copper wire during
fusing (2012 degrees F) must be contained in a safe area.

I'm surprised a fuse link wire was used in a modern installation,
although I have seen it built into wiring harnesses in recent
automobiles, especially near the battery. (It's that funny looking,
skinny, 3 inch section of the wiring harness inside shrink tubing that
seems to do nothing.) I think it is more to stop the battery from
exploding from a short in the starter cable or a faulty starter than
electrical fire prevention. All the other vehicle wiring would fuse in
an accident.

If this was an add-on system, I would have expected a straight forward
in-line fuse cartridge, one per battery, although it's a little more
expensive.

The key thing is WHERE did the short occur. If a grounded part of the
vehicle pierced the larger cable before the fuse link, then chances are
the fire was initiated by burning sheet metal and the fuse link wasn't
part of the scenario. That then changes the investigation as to whether
the pierced cable was insulated and installed  properly. (Ever notice
the fireproof abrasion sleeve over a starter cable near the frame?)

The event appears to be so catastrophic the small variables (a few amps)
that time-to-fuse and ambient temperature could cause are almost
meaningless.

You have an interesting task, but I personally think there is enough
existing data to determine the fusing currents without repeating these
tests except for demonstration purposes.

But I may be wrong........
Jack Daniel
============================================

Todd Ellis wrote:
> 
> Jack:
> 
> It sure does help!  Our guys are much more versed at much higher
> voltages, not the low voltages like you would find in a commercial
> long-haul truck.
> 
> 
> 
> whopping 109 inches.  Nothing was flameproof in this situation, and in
> fact, after a minor accident, the resulting fire lit the diesel fuel,
> and the truck and its driver burned up.  The battery bank was good to
> 2,000 amps which would represent a dead short across the three
> batteries.  The question is whether the 6 AWG cable was truly a
> ?fusable link? in this case.
> 
> 
> 
> Folks, this can happen?watch how you install your radios in commercial
> trucks.  We have a client who has had multiple mobile radio problems,
> all attributable to the local shop cutting off the power from the
> battery, then cutting off the connector at the cab and splicing in the
> new cable.  Take the time to de-install old DC cables and grounding
> hardware when you are installing a new radio.  Your client will
> appreciate it, believe me.
> 
> 
> 
> Todd Ellis
> 
> 
> 
> 
> 

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---

From: "arclight_arclight" <[email-masked]>
Date: Wed, 05 Mar 2003 10:05:29 -0000

> wire was supposedly designed by one entity to act as a fuseable 
link.  Yeah,

Todd: For the measurement techniques and hardware I think I'd engage 
a commercial DC powerplant vendor.  PECO 2 and Power Conversion 
Products come to mind; there are others as well.

I am certain that either of them could work with you on doing this 
job.  Gathering the necessary equipment to do it might be a 
challenge, because they usually do 24 or 48 VDC plants.  However, 
they might be able to simulate this for you in such a fashion that 
the results would be applicable to your problem.

There's a side note in all of this.  We typically do NOT design in 
the proper protection in low-voltage, high-current DC systems that is 
really required.  3 batteries in parallel?  Hmmm...if we were 
connecting 3 120 VAC circuits in parallel (assuming all phased 
correctly) we'd provide overload protection on each source.  How come 
we don't think about that when it's 12 VDC?  I say WE here because 
you probably wouldn't believe the number of folks who do precisely 
what you described with NO protection of ANY kind for circulating 
currents between the batteries.  Get a shorted cell in one battery--
how much circulating current will there be between the 3 batteries?

Maybe we need 1,000-volt batteries in our stuff (snicker).  Wonder if 
we'd think more about protection then?

Dave Maples

---

From: "Todd Ellis" <[email-masked]>
Date: Tue, 4 Mar 2003 09:50:32 -0500

Hey Rik:

Yes, but they are hesitant since this is post-accident, not pre-accident.
Can you say liability?

Todd

-----Original Message-----
From: Todd Ellis [mailto:[email-masked]]
Sent: Monday, March 03, 2003 3:41 PM
To: NEXTEL-1@yahoogroups. com
Subject: [NEXTEL-1] Looking for HIGH DC amperage...REALLY high

Todd Ellis

Booth & Associates, Inc.

Raleigh, North Carolina 

(919) 851-8770

[email-masked]

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<http://docs.yahoo.com/info/terms/> . 

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---

From: Rick Parrish <[email-masked]>
Date: Tue, 04 Mar 2003 19:36:08 -0600

Todd Ellis wrote:

> Folks, this can happen…watch how you install your radios in commercial 
I've been suprised how often lazy aviation mechanics fail to do this 
small extra effort for light aircraft radio installations. I once pulled 
what seemed like 10 pounds of unused wiring out from behind the 
instrument panel of an otherwise trusty little Cessna 150. It was neatly 
tie-wrapped but clipped at one or both ends - just as Todd describes.

-rick

---

From: Jack Daniel <[email-masked]>
Date: Wed, 05 Mar 2003 20:51:28 -0800

Hey Dave,

You have to be careful the batteries are in phase too. ;-)

Jack Daniel
===============================

---

From: Don Root <[email-masked]>
Date: Wed, 05 Mar 2003 21:07:37 -0800

> You have to be careful the batteries are in phase too. ;-)

Oh, man!  THAT must be why I have problems sometimes when I mount
them 90 degrees to each other.   :)

Don

---

From: Jack Daniel <[email-masked]>
Date: Wed, 05 Mar 2003 21:49:26 -0800

Getting batteries connected in-phase is a "digital" or binary problem; 
There are only two states: right and wrong..... unless you are using an
AC battery instead of a DC battery.

===============================================