Ok so I came out to my car this commonly warm/hot morning and the volt meter read just above 10 V. Car started reasonably fast but the starter struggled for power.

I drove for 10 min and came back. Turned car off. Checked meter and it read just under 14 V. Half an hour later the meter read just above 10 V again.
I have been running my errands today some 30 min drive and the car starts up each time but the starter is definitely struggling for juice, meter reading just above 10V.

What could drain the battery that fast?
No lights on or radio or anything. Alarm isn't going off.

When driving the meter reads just almost 14 V

Thanks!

I forget if my sig says it but my car is a 2000 a4 Quattro 1.8T ATW. 5spd

 

After a few days here it is:

My car will charge at 14V while driving and I can have every electrical accessory on without a hiccup.

After shutting down and checking the dash voltmeter, it says maybe 13 volts.

Within 5-10 minutes that will drop to just over 10 V.

Car starts every time but the starter struggles for juice.

Dead cell on the battery?

 

I would start by checking the fluid levels in the battery cells. Battery could just be dead as well, how old is it?

 

The battery is at least 3 years old since I never replaced it. I seem to remember the previous (and first) owner of the vehicle saying he bought a new battery for "recently" maybe within a year or two of when I bought the car from him.

I'll check the fluid.

 

Probably battery. Sounds like the alternator is charging just fine, and if this is a relatively new occurrance then I would suspect the battery.
In my experience car batteries will sort of degrade over time to the point where they begin to show noticeable characteristics like you're experiencing, and soon enough they won't even let you start the car.

You can check current draw with your voltmeter (put it in series between a battery terminal and the associated battery cable) and make sure you're not seeing a super-high draw while all the lights are off / doors locked / etc.

 

Hey so I tested current draw and found it to be about 32 mA. I had also found corrosion on the neg terminal so I cleaned that up. After that and your description I felt confident it was the battery's time. So I replaced with the same model, a Bosch 48-690B.
Everything has been good for two days now.
Thanks for the info