So I just purchase a pc680 two weeks ago and it's been perfect. I did not drive my car for an entire day and the next day it would just click when you try and turn it on. I have a Clifford arm with the proximity sensor set to almost the highest point. Could it be the alarm draining the battery so quickly?

The alarm sounds like the case. Over time the battery will get even weaker, mine needs a Battery Tender to keep it up if i dont drive it for a week or two. This is my second PC680 and i am going back to a full size battery now, but in the trunk.

Just ended up getting a bigger battery, thanks

Good call for something like your car. I always ran a battery tender on my Odysee's and other light weight battery's.