Just got a Mophie Juice Pack Pro for my 4s, used, off eBay; no instructions. I fully charged both separately before I put them together. My two questions: 1. What's the best way to use: Run the phone battery down, then turn on the Mophie, or turn on the Mophie from the beginning and draw both down together? 2. If I leave the phone in the Mophie and charge the Mophie, does that charge the phone too, or do I need to charge both separately? Thanks in advance.