depletes as in battery drain to 0 capacity when its store inside the notebook without use(with notebook shut down)? cant really give ya solution since im not using it. afaik, only Z and SR having battery drain issue but it wont run out until 0% capacity for say 1 day store inside the notebook.
so far only one P user, which is tpl, you may message him about this.

same goes to mine.. if the battery left intact. try pull out the battery it will store 100% power for more days. but if u keep it like a week or so it will discharge. Try go silent room attach the battery u will hear some funny 'eee' sounds from your P even when its shut down. I had the same funny sound with my fujitsu u1010.