Your Echo Cell rechargeable lithium batteries are charged and ready to use. Insert one lithium battery into the Echo Cell cartridge matching the polarity and screw the end cap on. Insert into your Echo transmitter positive side down. The Echo Cell should provide power for approximately 20 hours of use. These lithium batteries are specially designed with a protective circuit that will allow the operation of the battery until completely dead without harming the battery. Only use the provided UM charger when recharging your Echo Cell batteries.