Power pack
From Tardis Wiki, the free Doctor Who reference
Power Packs are a common form of enerating power. They are similar to batteries. When Nyssa found a number of power packs it proved the crash must have been light and passengers may have survived as power packs are fragile. The Terileptil's used them to power their mind controlling braclets. They were easily removed however quickly disabling the mind control capabilities.(DW: The Visitation)
