I have the same setup i450 with 12volt kit. I have 3 of the 12v kits and 7 batteries. I get about 5 weeks out of the batteries. I've had as many as 800 pics, that was after 3 weeks and the battery was still good. In the long run this is going to be much cheaper for you! Plus, you'll get more pictures because your camera will not be dead as often.

You'll probably want a spare battery too. Batteries plus carries them, the only problem w/ them is the terminals are pointing the wrong direction and will hit the side of the case when you are putting it in. Be carefull not to disconnect the hot while putting the battery in the case.