Tech support said it's by design as RAID controller uses more power but then the default config renders the only sleep mode available almost useless.
Followup for [URL] In my Latitude 5530 when storage is in RAID in BIOS the s2idle drains batter at the rate of 56% for 24 hours. If I switch to AHCI mode the drain is 14% per 24 hours, it looks like there's a problem with Dell's RAID implementation. I am on the latest BIOS/OS versions
s2idle drains battery fast with RAID mode