Date: Fri, 14 Dec 2001 01:27:05 EST
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: 2nd battery relays & the Hella in particular
Content-Type: text/plain; charset="US-ASCII"
In a message dated 12/13/01 12:47:48 PM, dbeierl@ATTGLOBAL.NET writes:
<< but your finding that #10 wire requires a 20-amp
fuse is consistent with the theory.
>>
David,
I most strenuously object to your misuse of the word "theory" here. The
restivity variation of wire by diameter was well established experimentally
long before the birth of the parents of the listees. The theory of the
variation of restivity with cross-section of the metal was postulated,
promulgated and verified so long ago that the original archival journal paper
is probably in need of chemical restoration (certainly well known in
Maxwell's time).
The resistivity of copper wire (as you well know) is given as ohms/square.
The resistance of a wire is directly (actually inversely) related to its
cross-sectional area and its length. Any segment of wire will have a net
resistance. For a given current flow through the wire, there is a
corresponding voltage drop. At 15 amps, a 1 ohm resistance will have a
voltage drop of 15 volts. Etc., etc.
All well and thoroughly explained and discussed in the archives. For the
detail, filter out the shorter anecdotal diatribes and read the lengthier
discussion (this exasperated comment is not directed to Dave, but to the
others who think the issue has never been resolved in previous discussion).
As I have placed into the archives on several previous occasions, the relay
systems works, the isolator works and the adjustable Bosch voltage regulator
works perfectly. Been using the adjustable voltage regulator to dial in the
best charging voltage at the starting and deep cycle batteries for somewhere
between 5 and 15 years. As I have also indicated, I have chosen the wire
gauge used in my Westfalia according to two principles:
1. Minimize the voltage drop!
2. Equalize the weight distribution of the vanagon from right to left!
My use of two 00 cables from the battery to the front fuse box and
independent 00 cables for right and left headlights serves both purposes. At
last check, I had right around 3% of the overall traveling mass devoted to
copper and lead.
The essence of the relay solution is the triggering by the alternator, and
the diode to block reverse flow. If the relay didn't work, then the
implementation is erroneous (bad, wrong, disingenuous, etc.)
Archives, archives. We need a FAQ committee to weed out the chaff! Theory
indeed! Reserve the word theory for the concept of the spherical chicken!
Frank Grunthaner
