The Shure SB930 is a rechargeable battery designed for use with MXCW640 Wireless Conference Units. It can power the MXCW640 for over 11 hours. Keep track of the charging status with the 5-segment LED meter. If you use the SB930 with the MXCWNCS Networked Charging Station, the unit will take only 1.5 hours to achieve a 50% charge. Wait 4 hours, and you'll have a full charge.