[T3] Electrical questions

[Jim Adney]

On 24 Aug 2015 at 22:57, Sean Bartnik wrote:

> Dave mentioned that a fully charged battery should read 6.6V so perhaps I need to put mine back on the charger.  I may have taken it off prematurely, I was thinking 6.3V for some reason.  More below:

6.6 sounds high to me. That would be equivalent to 13.2 on a 12 V 
battery, which you'll never see unless the battery is charging or 
JUST taken off the charger. I think your 6.3 or 6.4 is closer to the 
mark.  

> > On Aug 24, 2015, at 10:45 PM, Jim Adney <jadney at VWType3.org> wrote:

> > The one voltage you got that bothered me was the 7.5 V from the 
> > generator at some point.
> 
> 7.5V was only at D+, I was curious to see what was coming into the VR from the generator.  I never saw higher than ~7.01V on the B+ side of the regulator with the engine at high rpm.

I don't know why there would be that much voltage drop across the 
voltage regulator, unless you had a lot of load on the generator at 
the time. Once you're above cutoff, the voltage regulator should look 
like a shunt with a max voltage drop of about 0.2 V. At low load, I'd 
expect less than 0.1 V of drop.
 
> > I suspect that there was some other starting problem that got you 
> > started down this path, but, for the most part, your charging system 
> > sounds like it is doing okay.
> 
> I suspect my original problem was just poor battery maintenance on my part; it hadn´t been on the charger since I bought it from Keith back in April(?) and there has been a lot of short trip driving over the summer in city traffic and some periods of sitting while I was out of town, etc.  I think the battery just became discharged naturally and it was good enough to start until suddenly it wasnTMt.  ITMll have to eep a better eye on battery condition from now on.

But I don't seen any sign of poor battery condition. If it is 
cranking the engine well, then it's in good condition and in a good 
state of charge. If it was just barely managing to turn the engine 
over, then that's a different story.

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