65 amps is a good bit of juice.
One thing you want to be aware of is the ability of your wiring to be able
to handle that much amperage. Wires have resistance, this resistance is
dissipated by heat. The resistance of a conductor is proportional to it's
length and inversely proportional to its cross sectional area.
What that means is you need to know the length of the wire and it's circular
mils.
I have a formula if you want to get real tecky.
R= Resistance
P(Rho)= Resistivity
P= Power, watts
I= Amperage, amps
E=Voltage, volts
L= Conductor length, feet
A= Cross-sectional area, circular mils
so
R=E/I R=P/IxI R=pL/A
Resistivity values for standard stranded uncoated automotive wire are 10.786
ohms-circular mil/foot at 25c.
The circular mils of standard automotive gauges are;
10 awg = 10,380
12 awg = 6,530
14 awg = 4,110
16 awg = 2,580
18 awg = 1,620
20 awg = 1,020
Here is some very basic stuff that we need to remember to think about since
sometimes it looks like Lucas didn't!
The current carrying capacity (ampacity) is defined as the current a
conductor can carry before it's temperature rise exceeds a permissible
value, (MELT DOWN). The correct conductor size insures that the heat
generated by the flow of current through the conductor plus the heat of the
ambient temperature does not exceed the thermal rating of the insulation.
The factory OEM wire in Triumph automobiles is an SAE J-1128, rated at -40c
to +80c. It's made of PVC and the wall thickness is from .031 for 10 awg to
.023 for 20 awg. It is commonly referred to in the industry as GPT.
All of this might seem a bit anal but if you take the time to run some of
these numbers you may see that the 1,000 watt amp that you just installed in
the trunk may have a very good chance to cause you LBC to melt! These
formulas also will work with that drop cord you have running 200 ft that you
have a fan, welder, radio, drill and the fridge plugged into.
Why is that drop cord getting so hot?
-----Original Message-----
From: spitfires-owner@autox.team.net [mailto:spitfires-owner@autox.team.net]
On Behalf Of James Carruthers
Sent: Saturday, August 16, 2003 1:17 PM
To: spitfires@autox.team.net
Subject: Alternator Wiring
Hello Spitters,
My new alternator is installed and working... there is a spare terminal
on the back of the alternator (the dynamo only had one wire going to it)
- it's a big fat one... can I connect this to some 35A wire and then
straight to the + terminal on the battery (well solenoid would be
easier) - just as an extra piece of wire for the juice to come down?
Whilst I don't think I'll ever need the full 65A that the alternator can
give out - it would be nice to know that accessories such as a medium
sized domestic fridge and washing machine could be run off my cigarette
lighter socket...
Cheers
James
69 Signal Red Spit
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