Date:         Fri, 4 Oct 2002 23:13:14 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Sanity Check - Wire gauge for wiring SA headlights
Comments: To: Brent Christensen <sbsyncro@HOTMAIL.COM>
In-Reply-To:  <OE21NZxS6VqRACPMZuO0000a9b6@hotmail.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 08:22 PM 10/4/2002, Brent Christensen wrote:
>8.5 amps current draw, the voltage drop from 12.5 volts through six feet
>of wire are as follows:
>
>10 - 5.2%  (or 11.9 volts)
>12 - 8.3% (or 11.5 volts)
>14 - 13.1% (or 10.9 volts)

Ok, I see the difficulty.  You were calculating drop in volts and calling
it per cent.  The drop across six feet of 14-ga wire carrying 8.5 amps is
about 0.13 volts at 77F and about 0.15 volts at 150F.

It's a linear relationship, so I can just drop this little table in here
for gauge vs voltage drop at ten amps and ten feet.  Y'all can multiply and
divide from there (my numbers are for 150F, figure a few per cent less drop
at 77F).  The only factors are the current and the resistance, so for a
given current you can just add up the drops from various segments of the
line.  Don't forget there are losses at the connectors too.

E (volts)I (amps)FtGaohm/k-ft
0.00571010"00000.057
0.0073"0000.073
0.0092"000.092
0.0116"00.116
0.014610.146
0.018420.184
0.023230.232
0.029240.292
0.036950.369
0.046560.465
0.058670.586
0.073980.739
0.093290.932
0.118101.18
0.148111.48
0.187121.87
0.236132.36
0.297142.97
0.375153.75
0.473164.73
0.596175.96
0.751187.51
0.948199.48
1.192011.9



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