Flew a mission this AM and the battery indicator at the top of the left panel was an empty red icon. I was using a full battery?! That notwithstanding, I ignored it and flew about 16 minutes, finished the mission and landed safe. Thought I should pass that along 
Thanks for passing this information along to us! Iām curious to know which version of the app are you currently running? One suggestion for you is to recycle power on your drone, controller, and device if you notice incorrect displays on the app. Doing so will help clear out any conflicts and improve app performance. Please give that a try moving forward and let us know if the problem persists!
Happy flying!
Stephanie
Current version of app.
Power was recycled and app restarted.
Using iPad dedicated to flying drone only; DJI Go, Litchi, AirData and now DroneDeploy.
FYI - It displayed battery percentage on previous DD missions.