Being a question that crops up now and then, I'd thought I'd put up my thoughts on my experience with Batteries Direct and my purchase of a D35 Yellowtop suitable for the RX-8, available here:
http://www.batteriesdirect.com.au/shop/ ... 0/d35.htmlNow as it is a deep cycle battery its great for those of us who don't use their 8 as a daily, so the battery may not be charged for weeks at a time.
The installation was easy, the battery is smaller than the OEM housing, so it fits without issue. However because it is smaller I ran into three problems:

1) The battery sits lower that the OEM one, meaning the battery holder does not completely hold the battery down, new holder is cheap and easy
2) The post is slightly narrower that the stock size, and my clamp was slightly worse for wear. Though I made connection, I'll be replacing the clamp for a tighter fit, again cheap and easy
3) As the battery sits lower, the positive connection doesn't completely reach. Either a case of putting something under the battery to hold it up, or in my case trim the plastic to allow the connection to sit nicely

After fitting the battery I had a few 'glitches' that needed resolution. Drivers side window didn't do its auto up and down, the DSC light was flashing and the Traction slippery light was on. Had to do an ECU reset (car on, turn wheel lock right, then lock left) which immediately resolved the flashing DSC. The auto window function and traction light both went away the next time the car was started. I imagine this wouldn't have happened if power was maintained to the system when replacing the battery.
Battery fired up straight away, looking forward to some hassle free starting now
