The HP Smart Array P840ar Controller is a refurbished RAID daughterboard controller for managing SAS and SATA storage connections. The listing identifies it as reference 848147-001-RFB, corresponding to HPE part 848147-001.
It provides two internal x8 mini-SAS double-wide ports for connecting storage, plus 2GB of flash-backed write cache. Supported transfer rates are up to 12Gb/s for SAS and 6Gb/s for SATA. The battery is not included.