Originally Posted by WolfX5

Optima makes blue, yellow and red-top batteries. I can't speak for the yellow or red-top varieties but I've been using an Optima blue-top marine battery in the X5 for a year and a half and it's been outstanding. I'm not sure why Gresch felt the need to post (twice) that he doesn't like Optima batteries. Though he's entitled to his own opinion it seems a little slanted since he's never actually owned one of their many fine products.
:flame:

The Optima blue-top runs about double what an equivalent Bosch/Pepboys replacement costs but it is deep-cycle so you'll have all of the associated joys of knowing that you won't permanently kill your battery the next time you leave your lights on or leave your car parked in an airport for several weeks at a stretch. In all fairness I should warn those who are interested in the Optima blue-top that the battery is taller than what is typically installed in an X5. For my particular deep-cycle application (I run a 3000 watt/120v power inverter for power tools), I went nuts and got the 238mm BT DC 5.5I which required me to custom-fabricate 3 brackets to lift the air compressor. Additionally I had to permanently forego having the spare tire installed to make adequate room for the battery. However he Optima blue-top also comes in the space-saving 200mm BT DC 4.2 and the more starting-friendly BT SLI 4.2 also at 200mm. These would be a better choice for those who want deep-cycle capabilities but don't want the headaches of a bracket modification.

Here's some popcorn for the commercial below...:popcorn:

"(Optima) are the batteries that we used on the Warn Glacier Expedition in Iceland. They performed beautifully and seemed completely unaffected by the cold. They worked for hours at a time as we winched the Jeep up and down Hvannadalshnjukur mountain and across Vatnajokull glacier."
Barbara O'Donnell - Peak Communications