Battery? Alternator? Something Else?

[skadakia15]

So here is my issue:
1999 986 had been running well without issues, ~70K miles, 5 speed.
4/17 car wouldn’t crank (clicking noise only), had it jump started and I bought a brand new battery and replaced it on 4/18. Car ran fine without any problems until this morning 4/21 it again wouldn’t crank. I did some testing with a voltmeter and here are the numbers on the new battery (all numbers tested at the battery posts):

4/21 0700 - 10.8 Volts

After driving to work (25 miles) - 12.8 Volts with Car OFF

4/21 1700 8.8 Volts (again car wouldn’t start, in the interim it had been off, presumably no electrical load). Had it jump started.

After driving home (25 miles) without a problem - 13.9 Volts with Car ON

14.5 Volts with Car ON Full Electrical Load

Car OFF dropped to 13.8 Volts

One hour later 13.2 Volts, cranked it and started right away (dipped to 11.6 during crank) then came up to 14.5 with it running. Car off back down to 13.2.

I know this is a long post with a lot of numbers but I’m hoping you guys can help me sort out what the problem is. My thoughts are that the alternator is working appropriately given the above readings. I just can’t figure out why I’m losing charge. Any thoughts, ideas, experiences are much appreciated. Thank you.