I went with an AGM Battery from Autozone, it's been fine so far, I would suggest looking up AGM batteries for X5, there are a lot of threads discussing AGM vs Lead Acid out here, I choose AGM cause of the way I drive.......there are times when my X5 sits for 2-3 weeks without going anywhere and then if it goes....it might be for a short distance and then sit again for 2-3 weeks.