I've been flying several times this week, most recently yesterday with no problems. Today I put in a fully charged battery, turned everything on, got good Wifi connection, started the motors, pushed the right control stick up to take off. The motor speed increased slightly but not fast enough to take off. Replaced the battery with another fully charged with same results. When I put it away yesterday everything was fine, this morning squat. Any suggestions as to what to look at? Thanks for your time.