Question about Nine Eagles Sky Climber 3G (Mode 2/Futaba Protocol)

Have you looked at all? There is a battery linked under Accessories and the specifications tell you everything you need to know about the battery:

Battery properties
Running time 15 min
Charging time 60 min
Battery type LiPo
Number of cells 3 x
Capacity 1800 mAh
Voltage 11.10 V