A spacer assembly, comprised of a plurality of rigid spacers, is provided that is configured for use with a cell mounting bracket within a battery pack. The spacer assembly maintains the positions of the batteries within the battery pack during a thermal event and after the cell mounting bracket loses structural integrity due to the increased temperature associated with the thermal event. By keeping the battery undergoing thermal runaway in its predetermined location within the battery pack, the minimum spacing between cells is maintained, thereby helping to minimize the thermal effects on adjacent cells while ensuring that the cooling system, if employed, is not compromised. As a result, the risk of thermal runaway propagation is reduced.