Date: Tue, 16 Dec 2008 15:09:01 -0800
Reply-To: mdrillock <mdrillock@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: mdrillock <mdrillock@COX.NET>
Subject: Re: Original Battery Wire Gauge
In-Reply-To: <E1LCibB-00053z-LP@fenris.runbox.com>
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
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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>>
>
> ----- End Original Message -----
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