I stacked two 3.7v 1200mha batteries on my little quad and it would get up off the ground and fly around like it was dragging a parachute. I knew it was too much weight, but I had to try. I got it up about 75 feet and accidentally switched off my transmitter trying to open the sunshade on my monitor. Needless to say, she hit the ground hard and bent a prop. I replaced it real quick and took off one of the batteries. I threw her up in the air and she just did some weird flips and wouldn't stop until it hit the ground again. These little 8.5x20mm coreless motors don't take too kindly to being bashed around. One of them was turning really rough when I spun it with my fingers. Looked a little out of alignment too. Anyhoo, I ordered 4 more and will then get to learn how to strip down the quad and replace the little motor. I really am enjoying test the limits of this toy grade quad so when I'm ready, I'll build me a Hobby Grade Aerial Platform and settle down into a serious mode of aerial exams of structures and bridges for the local government. That's until I make enough money to hog wild with the real stuff!