Date:         Wed, 7 Aug 2002 12:57:24 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Headlight rewiring
Comments: To: rodney.woten@LENNOXIND.COM
In-Reply-To:  <TFSBKFBJ@lennoxind.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 11:34 AM 8/7/2002, Rodney Woten wrote:
>Doesn't splicing the new wire into the existing, smaller gauge, wires at
>the plug, defeating the purpose???

Not really.  It's not ideal, but as long as you stay within the amount of
current that the smaller wire can safely carry without overheating it will
work ok.

Reason is that you're concerned with total resistance from battery to
ground -- ideally you want the entire resistance of the circuit to be the
lamp itself.  That's not possible unless you're into superconductors, so
you approximate it as well as you can.  For a given current,  a given size
of copper wire will drop (lose, expend, turn into heat) so many millivolts
per foot -- your aim is to keep the total waste between battery and ground
to less than a volt, and preferably less than half a volt.   A foot of
skinny wire will only contribute a tenth as much waste as ten feet of
skinny wire.

The other places you waste voltage are at switch/relay contacts, and at
connections.  If you're dropping more than a few millivolts across a
connection it's a candidate for cleaning up.  If you're dropping half a
volt in a twelve-volt (13.6 volt) circuit, then you're wasting about 3.5%
of the total power -- about 7 watts in a 200-watt circuit.  It doesn't
sound like much, but a curious characteristic of incandescent bulbs is that
visible light output goes up with roughly the fourth power of the voltage
change.  Unfortunately, bulb life (at least for a standard incandescent,
not necessarily a halogen) goes down with roughly the *fifteenth* power of
the voltage, so there's a very definite tradeoff.  Folks who upgrade their
wiring to get every possible watt to the bulb are going to be changing
bulbs noticeably more often.

david

>If I could get to the terminals inside the plug, I'd rewire

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"