A second battery you should definitely have to start with the movies. After that comes with the HF-S 21 BP-809 an hour endures, I chose the same replacement battery for the BP-827. The battery offers Although the desired runtime Reserve (real data have yet to be determined) However, the battery is built as far back on how the viewfinder can be pulled out of the camera. The battery looks so when he did not fit the camcorder and interfere with use of the viewfinder. I would recommend the BP-819th The price performance ratio (Acquisition cost / duration) is a little worse, the battery is for smaller and better suited to the camcorder.
PS: All who want to buy a Canon battery, I can only advise. The cheap batteries are quickly warm, also the remaining term does not appear as in the original battery, which is anything but handy when filming.
