So I am new to the DJI and drone scene but ran into a big sticking point for me. I am flying the P3 Standard with an iPhone 6s as my screen. I have noticed that when I run the DJI GO app and are connected to the drone my battery suffers significantly. I went out last weekend and use one battery for the drone but my phone's battery drained and my phone shut off while in flight and probably 1000feet away and high in the air. Not a big deal because I can fly it with no screen or use of RTH. My issue is that my phone died faster than my drone. Is anyone else having these issues? I  on the latest versions of everything.

Your iPhone 6 is fully-charged before flight, and have you turned off all other background programs?
Please go to settings--General--Usage--Battery usage, you will check the battery usage for each programs on your iPhone.