This is an
Odyssey PC680. It weighs a hair over 15 lbs, has great cranking, and is supossed to last well. I just put it in this weekend, so I don't have anything to say except that at 10* F my car fires right up. It's tiny, as you can see. I fabbed those rails to hold my big battery, and this slips right down in on it's side! As you can see, it's only as tall as the stock is wide, since the stock retaining rail fits right over it.
This battery won't last as long if you're going to drain it by sitting with the radio/lights on. I also am holding on to my stock battery for winter, so I have a super-reliable battery in the cold weather up here.
So, you may want to think about putting a large battery in the trunk. I fabbed my mounts in a few minutes, and they are very solid. If you used angle aluminum without the holes, and some prettier screws, you could make it look really good. The bars that hold the stock battery slip right in those holes I enlarged on the side rails, so it's very tight. That way you keep the battery out of the heat of the engine bay, which helps life a LOT, and you get more room for the CAI. You also get better weight distribution!
Or, like Brapple says, you could just measure it and take your tape measure to the store, if you're happy with this setup.
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I know 
