The SB904 rechargeable lithium-ion Battery powers all Shure GLXD+ transmitters (sold separately) for up to 12 hours on a full charge. The battery supports charging from the front panel of the tabletop and rackmount receivers, in an SBC10-904 sled charger, or while still in its respective transmitter using the SBC10-USBC wall charger (all sold separately). The SB904 also yields a 1.5-hour runtime after a brief 15-minute quick charge! It's always good to have a backup. Get yours today.