Sounds like you have a software / app glitch somewhere. Many here, including myself, have been running Developer betas on the same device without any overt battery drain.I'm a tad bit sceptical about this one. Developer Preview 7 (the last one before this release) has been the worst of bunch for me with a serious battery drain on my iPhone 7 Plus. I'm going from 100% to 30% in a matter for 3-4 hours without really using my phone. Hopefully it's fixed in the final release, but as every other 10.3 Preview worked better I'm not entirely sure what's going on. But as I'm already having battery drainage, what do I have to loose.