Relion 5200 mAH battery runs at 7.4V and must be regulated to operate radio system.  Flat configuration.  No returns on batteries.

The Arizona Heli Regulator is specifically designed with RC helicopters in mind. It handles very high currents, has two separate voltage outputs: 5V for the gyro/tail rotor servo, and an adjustable 5V-6.00V for the receiver and other servos.  The optional pin switch acts as a solid state switch, eliminating the unreliable conventional mechanical switch.  Battery not included.