It's possible, but you could test for certain by disconnecting the alternator charge cable from the rest of the system overnight and see if it still drains.
I realize that's not a "test" per sé, but it'll isolate things pretty certain.
With your setup you can even disconnect it at the Mega-Fuse for convenience.
How long does it take to drain the battery? If just a few hours then it's likely the alternator. Not much else drains a battery that quickly except when the battery itself is going bad.
Unless you have some other fancy electronic doohickeys plugged in somewhere?
Batteries do just go deal all on their own sometimes. We see it happen all the time too. Probably about 30% to an alternator's 70% or thereabouts.
If you disconnect the alternator and it still dies, then it's something else, such as the battery. If that happens, then you disconnect the battery and see if it still dies. If it does, then you know for certain it's the battery alone.
As said, very possible to be an alternator though, as they do fail. Could be the internal diodes, or it could just be the regulator going out. not sure how to test for that.
When the engine is running, what is the charge voltage reading?
Not really a long official warranty on them unfortunately. It's "only" 30 months, so you're good! If it turns out to be the alternator after all then, give us a call and see what we can do to take care of it.
Paul
