Thank you for your inquiry.
Please check the information here:
Copter Battery: 3.7V 75mAh Li-po Battery
You don't need to buy an Copter Battery for it. You just need to buy remote control battery when it is used up.
Because the original design of this helicopter is the aircraft battery power supply from the remote control battery. The aircraft is not with the charging line and charger . The remote control has a charging socket and the aircraft charging interface at the bottom of the aircraft.
You can check these links for your reference: http://prntscr.com/dukoam
Please feel free to contact us if further questions.
Thank you for your attention.