My alternator killed my battery.

[NikFu S.]

Or it helped anyway.
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Things like this usually take a good deal of thinking and research to figure out, but it dawned on me yesterday while contemplating a few things.

I picked up a battery/alternator charge sensing doohickey at Wal-Mart for some $15. It plugs into the lighter socket and has a neat LCD/LED display.
It shows battery charge, alt output, and the LEDs indicate whether the current alt output is enough to charge the battery.
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Square one.
I replaced my alternator some months back with a somewhat high output, 110A model.
Remembering the thread discussing alts, apparently to aquire more high end, high revving amperage you need to sacrifice low end output.

The Wal-Mart meter thing reflects this as the battery does not charge at idle. An average of 11.5v runs through the system at idle.

As the temperatures drop, high voltage is required to keep the SVX happy. When it was about 20*F out, ~13v was enough to make the light green, and today at about -5*F (-21*C), it needed around 14.6v. Some of it has to do with the fact it's always dark when I'm on the road so the lights are on, and recently I've been running the heater to clear the windows. Sometimes like today, I actually felt kinda chilly.
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Some of the symptoms I was having was the vehicle was dieing at idle, and some mornings, would fail to turn over as there was not enough charge in the battery.
One afternoon I was slowing to a stop, and all the idiot lights came on and the lights dimmed. At that point I knew it was either the alt or battery, and this prompted me to get the meter.

Now that I have it I can read the thingy at stops and give it a little gas to keep it in the green. It was a distraction at first but I don't need to look at it much. Just glance at it while idling.
Sadly the battery will not hold a decent charge, but I'm going to see how that goes when temps warm up. So far I only need it to idle at about 900 in very cold weather, less as temps rise, obviously as less voltage is needed.
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The battery is pretty much dead every morning.
My XT6 had a feature and in the manual stated a capacitor of some sort seperate from the battey holds a small charge strong enough to start the car in dead battery conditions. The way you engage it is to turn the key back and forth 3 or 4 times and then hold it.

So far this has been working in the SVX. I'm not sure if it's supposed to or if it could be damaging the starter so if you have insight on this, let me know.

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Interesting note:
The autostart will start the car regardless of the battery o.0