Meaningless battery level in droidPlanner 2

The battery level in Droid Planner 2 (and 1 for that matter) as run off my Sony Xperia cycles down and up from 120% to 9% then back up again. It will do this several times in 10 minutes. The voltage it registers is pretty much correct - the % is meaningless. Ideas please as this should be genuinely useful!

It’s a problem with the configuration of your current sensor on your copter. Please review that, and also the battery capacity parameter.