TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Assembly: In the battery assembly, the container section of the battery cell pocket includes a first major heat transfer wall and a second major heat transfer wall, the first major heat transfer wall including a first indent section curving towards the second major heat transfer wall. The second major heat transfer wall includes a second indent section that curves towards the first major heat transfer wall. The first indent section is integrally formed as part of the first major heat transfer wall. The battery cell pocket includes a second spacer; the first spacer extends from an upper portion of the first major heat transfer wall of the battery cell pocket; and the second spacer extends from a lower portion of the second major heat transfer wall the battery cell pocket. The battery cell pocket includes a first major heat transfer wall and a second major heat transfer wall; and the battery assembly further comprises: a first battery cell disposed within the battery cell pocket; a second battery cell disposed within the battery cell pocket; and an intermediate piece disposed between the first battery cell and the second battery cell. The casing comprises a baffle extending from the container section into the coolant chamber. It further comprises: a cover assembly coupled to the casing. The cover assembly comprises a plastic sheet. It further comprises: a first battery cell including a terminal, and the terminal extending outside of the battery cell pocket. It further comprises: a battery cell retainer component extending across a length of the casing, the battery cell retainer component including a protrusion extending into the battery cell pocket to contact a first battery cell disposed within the battery cell pocket. It further comprises: a frame including an inner cavity and an outer perimeter, the inner cavity including a first battery cell disposed, and the outer perimeter configured to be substantially equal to or smaller in size than a cavity of the battery cell pocket. It also comprises: casing including walls defining a coolant chamber; and battery cell pockets disposed in the coolant chamber, each battery cell pocket including a container section, a lip, and a first spacer, the container section having a first major heat transfer wall, a second major heat transfer wall, a first minor heat transfer wall, a second minor heat transfer wall, and a bottom wall, the first major heat transfer wall including a first indent section extending towards the second major heat transfer wall, the lip surrounding the container section and including a casing adjoining section and a pocket adjoining section, the casing adjoining section extending from the first minor heat transfer wall, and coupled to the casing, and the pocket adjoining section extending from the first major heat transfer wall and configured to couple to an adjacent lip of an adjacent battery cell pocket, and the first spacer protruding outwardly from the first major heat transfer wall or the second major heat transfer wall. The battery cell pocket includes a second spacer; the first spacer extends from a lower portion of the first major heat transfer wall; and the second spacer extends from a lower portion of the second major heat transfer wall. The casing comprises a baffle extending from the container section into the coolant chamber. It further comprises: cover assembly coupled to the casing. The cover assembly comprises a plastic sheet. It further comprises: battery cells corresponding to and disposed within the battery cell pockets, each battery cell including a first surface in contact with the first major heat transfer wall and a second surface in contact with the second major heat transfer wall; and battery cell retainer component extending across a length of the casing, the battery cell retainer component including a protrusion extending into the battery cell pocket to contact a first battery cell. It further comprises: frame including an inner cavity and an outer perimeter, the inner cavity including a first battery cell disposed, and the outer perimeter configured to be substantially equal to or smaller in size than a cavity of the battery cell pocket.