[T3] Voltage Regulator

[Jim Adney]

On 9 Nov 2010 at 12:07, Tim Keohane wrote:

> Did some more fussing on this. I hope I didn't trash my battery. It's  
> a 500 CCA 625 Amp/hour battery. 

500 CCA is a peak current rating (Cold Cranking Amperes.) I'm not 
sure what the 625 is, but it's not Amp-hours, and Amp/hours are not a 
legitimate set of units. Group 42 batteries, which is what we use, 
are all about 45 Amp-hours.

> I have been charging my batteries when  needed thinking my charger
> "senses" the state of charge and reduces  the input as necessary. So I
> assumed @ 2 amps the battery never  received more than 2 amps, and
> that was reduced as the battery neared  capacity. 

With most battery chargers that is an valid assumption. Your previous 
message said 10 Amps for 24 hours, so 2 amps is a LOT better. If the 
current dropped as the battery charged then you probably did no harm. 
If you actually left it on the 10 A setting for 24 hours, that may 
have been a mistake.  

> I drove the car at night several times this past week. I've observed  
> that the idiot light is faintly glowing. I had to dim my dash lights  
> to be certain. It makes no discernible difference between high and low  
> beams. ( 110 x 2 or 55 x 2 ). I do notice the lights brighten when  
> rpm's are increased. Again high/low seems the same. Electrically the V  
> R connections shouldn't make any difference, but physically if the V R  
> has an issue, swapping the terminal connections at the V R ( fuse and  
> battery circuits ) would produce a noticeable change. I'll try that  
> next. I'm also earth strapping the components so I'm not chasing a bad/ 
> faulty ground.

Since your high beams draw so much current, I'd be surprised if there 
was no significant difference between highs and lows. A dim glow from 
the idiot light indicates a fairly large voltage drop (proportional 
to current draw) between the VR and the fuse box. You might want to 
check the connections at the fuse box to make sure that you're not 
burning up a connection there. The single wire carrying all that 
current terminates at the fuse box in a single 1/4" spade connector 
that has to carry all that current. That current also has to pass 
thru the headlight switch, the hi/lo relay, and, from '71-on, the 
ignition switch. None of those items are rated to carry this much 
current.  

I don't remember what year you have, but the '71 ignition switch is a 
one year only item, and almost impossible to find replacements for. 
If that's your year, you REALLY don't want to fry the one you have.

Swapping the wires at the VR is a reasonable thing to try, but I'd 
bet against finding any difference.

> I've seen some conversions to alternators. Are there any comments  
> regarding this. It seems that if I had 50 amps charging capacity I  
> could eliminate this problem.

A 50 Amp alternator conversion would solve the generator end of the 
problem, but it won't keep you from burning up later links in the 
chain. You could get around those problems by adding separate wires 
and relays to handle the actual headlight current.

> I'm researching lower wattage bulbs, and have yet to power up the
> radio/cd player. Standard alpine unit, but does need 12 volts.

The radio should be no problem. Modern halogen 60 Watt bulbs are 
really pretty good, even if they don't come with the bragging rights 
that come with the 100 Watters.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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