for the advice, but the best choice is to have 4-5 extra batteries available in you packet - their size and weight gove you such possibility. Espesially if the batteries cost is $10 for pair!
And one short comment about zoom:
Question: Do you have any problem to play with HD1a using zoom like 5x, 6x?
Answer: If you have 10x max - 5x is in the working zone; if you have 5x max - your real working zoom no more than 3-4x.