All the batteries at autozone will fit. The battery in the X5 is massive so those batteries simply go in there. They are all smaller than the current X5 battery.

I got one with 950CC and 110 storage capacity. It is smaller than the X5 battery but it is held in place by the old clips.

I run HIDs, DSP + 250WATT RMS Sub just fine. No problems.

It's not a direct fit but you have so much room to work with there that it will fit anything.

2001 3.0