Has any one opened up the controller would like to see a battery mode so you can balance charge it.any thoughts on this.

If it needs replacing before the drone is history (it should last 2-3 years) it is just a 18650 Li-ion battery as fb_43b9ftbKWM said. It takes six odd screws to get to it. Take back cover off 4 screws, take antenna cover off, 2 screws. You might also need to remove the antennas to gain full access. Hopefully it is not soldered in place