Date:         Tue, 16 Dec 2008 18:08:06 -0800
Reply-To:     M'obeechi <obeechi@RUNBOX.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         M'obeechi <obeechi@RUNBOX.COM>
Subject:      Re: Original Battery Wire Gauge
Comments: To: mdrillock@COX.NET
In-Reply-To:  <4948350D.4000804@cox.net>
Content-Type: text/plain; charset="iso-8859-15"

Ok, plugging Copper, 2/0 with assuming foot length, and 330 amps gives a voltage drop of 3.52 percent... and 11.577 volts on the load end of circuit, that sounds a lot better... so with a wire longer than stock, and with a Subaru, it would be good move to get a fatter than stock wire, it certainly couldn't hurt, like if your battery were ever weak... I have noticed sometimes some kind of lull right after starting, and then it goes away within a very small time frame. I just need to wait a second before moving into the highway. 

From: mdrillock <mdrillock@COX.NET>
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Original Battery Wire Gauge

> You are missing a key point. The current draw through the wire largely
> depends on the starter motor itself. It will only draw so many amps
> according to it's design and size. Using a much higher CCA battery does
> not change this. As long as the battery is big enough, making it bigger
> still just means it can crank for a longer time without the starter
> motor slowing down. You will never see even half of your 1150 amps, IMO.
> 
> If you look in the table for amps/wire size you can see that stock 2/0
> wire is only rated for 330 amps. I would guess that VW chose this as a
> suitable size for the larger starter 2.1 models got. Thus I doubt the
> stock starter current exceeds the 330 amps by much. Maybe someone else
> knows about how many amps would be expected.
> 
> (This topic brings up a problem seen in Subaru conversions perhaps more
> than stock motors. Before the alternator is charging, the fuel injection
> wiring gets its power from the starter motor post. Thus when the starter
> motor is cranking and the voltage drops there may be too low of a
> voltage for the ECU to work.)
> 
> Mark
> 
> 
> 
> M'obeechi wrote:
> > Wow.. I went to this site, and put in for
> > 1. Copper Wire
> > 2. 2/0 AWG
> > 3. 12 VDC
> > 4. 1150 Amps... I used this figure simply because the Sears Platinum Group 31 is rated for 1150 cranking amps
> >
> > The results:
> > 1. voltage drop 1.842
> > 2. voltage at load end of circuit is 10.158
> > 3. Percent voltage drop is 15.35
> >
> > That seems too much of a voltage drop... like the wire is a weak link in this setup... I think this wire length is longer than stock, and the battery is bigger, so to take full advantage of the cranking amps... but even with 4/0 AWG the voltage the results are:
> > 1. voltage drop 1.159
> > 2. voltage at load end of circuit is 10.841
> > 3. percent voltage drop is 9.66
> >
> > Is there anything that can be done to up the voltage again, like a relay or something?
> >
> > But then again, if I change to 4 AWG and reduce the length to 4 feet while keeping the Amps the same, the results are:
> > 1. voltage drop is 2.35
> > 2. voltage at load end of circuit is 9.65
> > 3. percent voltage drop is 19.58
> >
> > So even 10 feet of 2/0 AWG is better than 4 feet of 4 AWG
> >
> > From: mdrillock <mdrillock@cox.net>
> > To: M'obeechi <obeechi@RUNBOX.COM>
> > Subject: Re: Original Battery Wire Gauge
> >
> >
> >> For 86-91 models it is 2/0, one size bigger than 1/0.
> >>
> >> Here is a useful link for checking things like amps versus wire size.
> >>
> >> http://genuinedealz.com/voltage-drop.html
> >>
> >> Mark
> >>
> >>
> >> M'obeechi wrote:
> >>
> >>> I no longer have this wire, but I remember it being very fat. Called the dealer, and they couldn't tell me, but they agreed with me that it was fatter than 4 gauge. Saw some 1/0 gauge wire (pronounced one-ought, didn't know that), looks nice, but I think the original VW wire was fatter.
> >>>
> >>> Does anyone know the gauge of this?
> >>>
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> >
> 
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