CMOS & Real Time Clock perform an important function when the power is turned off, the CMOS battery maintains the time and date, thus insuring their accuracy when the system is once again restarted. We specialize in providing high quality CMOS & Real Time Clock Battery for COMPAQ laptops. All Genuine COMPAQ CMOS Battery is 100% Compatible, Meets or Exceeds Original Specification. Welcome to wholesale COMPAQ CMOS Batteries!