[AT] Tractor wiring

[Howard R. Weeks]

More on the same subject -
It takes twice as much current to do a given
job at 6 volts as it does at 12 volts.  For example: 12 volts x 12 amps =
144 watts.
144 watts / 6 volts = 24 amps.  If you had .1 ohm of resistance in the
12 volt cable, then .1 ohm x 12 amps = 1.2 volts dropped across that loss.
So that leaves you with 10.8 at the load.  The same loss at 6 volts would be
.1 ohm x 24 = 2.4 volts loss. That leaves only 3.6 volts at the load.  That
little bit
of resistance that is hardly noticable at 12 volts would keep a 6 volt
system from working.
To keep this resistance to a minimum, use bigger wire and really keep the
connections
clean and tight.

Howard Weeks
Harlem, GA




----- Original Message -----
From: "Spencer Yost" <yostsw at atis.net>
To: <at at lists.antique-tractor.com>
Sent: Wednesday, November 17, 2004 11:44 PM
Subject: Re[2]: [AT] Tractor wiring


Resistance is a function of current flow, therefore resistance is twice the
problem at 6 volts than 12 volts if the load is the same and cable must be
bigger to mitigate resistance losses.   I understand resistance is the
biggest reason 12 volts was adopted instead of 6 and 120 volts was settled
on for residential wiring.  120V was a compromise between "higher is
better" and too high is dangerous.

Spencer Yost
Owner, ATIS
Plow the Net!
http://www.atis.net

*********** REPLY SEPARATOR  ***********

On 11/17/2004 at 9:51 PM charlie hill wrote:

>Here is my question on this subject.
>
>Why are battery cables for 6 volt systems heavier than those for 12 volt
>applications?   Assuming both are powering a starter to turn a similar
>size
>engine (similar load), why would the 6 volt cable need to be bigger.  It
>flows more amps but less voltage and should flow roughly the same wattage
>in
>both applications.
>
>Charlie
>
>
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