The HP 854109-006 is a replacement laptop battery identified for the HP EliteBook 820 G4. Its ST03XL designation, also listed as ST03049XL-PL RT, helps match the battery to the corresponding part.
It uses lithium-ion cells in a 3-cell construction, with a stated energy capacity of 49 Wh and charge capacity of 4.25 Ah. These specifications describe the battery for replacing the corresponding part in the supported laptop configuration.