I'm about to pick up an LG G4 and in all the review videos, people say to have a 2nd battery ready to throw in since the phone has a removable back. What I'm wondering is how do they charge the 2nd battery. Do you need to open up the phone and switch the batteries out frequently to charge up the 2nd one? That would get very tedious and annoying. If there's something I'm missing, please fill me in! Thanks