The disclosure relates to a power battery and a battery module. The power battery includes: a case including two openings opposite to each other; an electrode assembly formed by winding a positive electrode sheet, a negative electrode sheet, and a separator disposed around a winding axis, the electrode assembly being disposed in the case, and two opposite ends of the electrode assembly along the winding axis being respectively disposed corresponding to the two openings; a first cap assembly covering one of the two openings, the first cap assembly including a liquid injection hole communicating with an interior of the case; a second cap assembly covering the other opening, the second cap assembly including a through hole communicating with the interior of the case; in a length direction, the liquid injection hole and the through hole are located on a same side of a central axis of the case.