TRACTION BATTERY PACKS WITH CELL-TO-PACK BATTERY SYSTEMS HOUSED WITHIN IRREGULARLY SHAPED ENCLOSURES

Traction battery packs are disclosed that include cell-to-pack battery systems. A cell stack/cell matrix of the cell-to-pack battery system may be positioned within an irregularly shaped enclosure tray of the traction battery pack. A block insert may be positioned at an interface between the cell stack/cell matrix and an irregularly shaped interior surface of the enclosure tray. The block insert may be configured to facilitate insertion of the cell stack/cell matrix into the enclosure tray, transfer compression loads from the enclosure tray walls to the cell stack/cell matrix, resist battery cell compression loads, etc.