[T3] Electrical questions

[Sean Bartnik]

Jim, Dave, and Keith, thanks all for the feedback.

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:


> On Aug 24, 2015, at 10:45 PM, Jim Adney <jadney at VWType3.org> wrote:
> 
> Sean,
> 
> That's an heroic bit of work you've done on this system, with a whole 
> lot of voltage drop data, but I don't see much that I'd find fault 
> with. My main thoughts are that if the starter cranks nicely, then 
> the battery and it's state of charge must be okay. None of your 
> voltage drops sound unusual; they're actually pretty good for a 6 V 
> system.

Good to know.


> 
> 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 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 wasn’t.  I’ll have to keep a better eye on battery condition from now on.

I am glad I was able to reduce that voltage drop to the coil though, I think that one being high might be what kept the car starting the other day.  

> The reduced voltage with the headlights 
> on seems a bit high, and that may be a problem, especially with 
> halogens, which are quite intolerant of low voltage (hence the 
> relays.) You sourced the relay power directly from the battery, 
> right?

I did, brand new 10 gauge direct from battery to the relays under the dash.

> 
> For the record, I'm currently working on a solid state voltage 
> regulator that I can adapt to either 6 or 12 V systems. If this 
> works, it should last forever and give much better regulation. 
> Getting a solid state solution for the 50 A cutout is challenging, 
> but I think I have a reasonably priced solution. I haven't tested 
> anything yet; so far this is all in the thinking stage: nothing in 
> testing, let alone production.

I’m in :-)

Mine seems to be working fine for now but it seems it’s going to be hard to find a new one if ever I need it.

-Sean
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