Common Sense RC Lectron Pro 6.6V 3200mAh LiFe Receiver Battery with EC3 Connecto

6.6V implies you won't need a regulator!

This 6.6V (2-cell) 32000mAh 5C LiFe (lithium iron phosphate, LiFePO4) receiver battery offers a great combination of efficiency and convenience. Our LiFe batteries have some special advantages over other battery options that make them perfect for usage in radio systems:

Voltage stays above 5V throughout your whole run, so you get more consistent servo speed and torque than with NiMH batteries
Somewhat lower voltage than Lipos implies you can securely connect 6.6V (2-cell) LiFe batteries to your receiver without needing a voltage regulator
3200mAh capacity is perfect for larger airplane and automobiles with multiple power-hungry servos
Separate EC3 connector and 14 awg leads for strong applications

Specs
Port: JR (Universal) Servo Port

Measurements:
Length: 86mm (3.39 in.)
Width: 49mm (1.93 in.)
Height: 19mm (0.75 in.)
Weight: 162g (5.71 oz)