It's always good to have a spare battery in your case. The Pansonic VW-VBG6PPK (7.2V, 5800mAh) is a replacement Lithium-Ion battery for the AG-HMC70 camcorder.
Specifications
Chemistry - Lithium-Ion
Capacity - 5800mAh
Output Voltage - 7.2V
Dimensions - 65.4 x 79.7 x 36mm (2.57 x 3.14 x 1.42")