The controller itself doesn't take lots of power, but the drives that make up the array do.
RAID is pointless in the vehicle and simply wasting power, IMHO.
If redundancy and data protection is what you're after, there are other ways to achieve it. If performance is your goal, then stick with a single drive.
If you absolutely must have a RAID array, get a beefier power supply like a DSATX or an Opus 250w.