Shure

Shure's SB900B rechargeable lithium-ion battery is a direct replacement for the SB900A battery, serving as a spare battery for the following transmitters: The SB900B features a thermal shutdown feature that automatically turns off the battery if it reaches a dangerous internal temperature. The battery provides up to 9 hours of continuous operation when fully charged, and is made to avoid "memory effect" so you'll always get a full charge. You'll also need the Shure SBC200-US charger (sold separately). Warranty: 2 years.