This handy ChargePAK F1 (rechargeable battery) works with compatible Pure radios giving you 'fit and forget'portability. It sits inside the battery compartment and charges up while your radio is plugged into its DC adaptor. The moment you detach your radio from the mains the ChargePAK takes over giving you the freedom to listen anywhere. Other key features include: Easy to install - can be fitted in seconds Easy to use -just fit and forget Charges inside the radio no separate charging unit required Increased battery life per charge over standard rechargeable batteries no need for throwaway alkaline batteries Provides hours of wireless portable listening