Cause:
Like any battery the computer CMOS battery can fail or lose its charge.

Solution:
If your computer is losing its time or date settings�� or you are receiving a message CMOS Read Error�� CMOS checksum error�� or CMOS Battery Failure�� first try leaving the computer on for 24-hours. In some cases this can charge the battery and resolve your issue. This often resolves CMOS battery related issues when a computer has been left off for several months. 


Compatible with the models :

IBM/Lenovo Thinkpad X30 X31 X32 T40 T41 T42 T43 R50 R40 R51 R52
T20 T21 T22 T23 T30

P/N: 02K6572, 02K6541, 02K7087, 02K7075, 08K8050


Package : 1 pcs of CMOS battery