Default Battery dies overnight while the phone is turned off.

My LG L90 is dying completely overnight when the phone is turned off. It's happening right out the box. I have yet to put a SIM in mine, and haven't entered my Google account yet (phone is for someone else). I think caught the phone turning itself on. I know when I put it in the box the first time after shutting it down, it was off. I went to put the charge in the box a while later and the LG screen was on. Happened two nights in a row now. I've read this issue other places so it's not just mine. Anyone know what's up?