Battery pack

A battery pack 1 comprises a core pack 4, a housing (7, figs 2 and 3), and an elastomer element 5. The elastomer element 5 has a first configuration in which the elastomer element has a first length and a first thickness and the core pack 4 is insertable into the housing (7, figs 2 and 3). The elastomer element 5 has a second configuration in which the elastomer element has a second length shorter than the first length and a second thickness greater than the first thickness such that the elastomer element presses against the core pack 4 and the housing (7, figs 2 and 3), thus securing the core pack in the housing. The elastomer element 5 may be a girdle surrounding the core pack 4 as shown. In an alternative arrangement, the elastomer element may comprise a cord (14, figs 4-6) located in grooves (15, figs 4-6) in the housing (11, figs 4-6) and grooves (13, figs 4-6) in the core pack (12, figs 4-6).