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 Thinkpad R40 Series 


R40-2681, R40-2682, R40-2683, R40-2722, R40-2723, R40-2724  
R40-2892, R40-2893, R40-2896, R40-2897, R40-2898, R40-2899  



IBM ThinkPad R40e Series

R40e-2684, R40e-2685
IBM Thinkpad R40 Series 


R40-2681, R40-2682, R40-2683, R40-2722, R40-2723, R40-2724  
R40-2892, R40-2893, R40-2896, R40-2897, R40-2898, R40-2899  



IBM ThinkPad R40e Series

R40e-2684, R40e-2685

IBM FRU: 91P8199 92P0991


Package : 1 pcs of CMOS battery