Hi, You had mentioned a recent LifeCycle Controller update, the update package updated your iDRAC firmware as well, if it is at version 2.10.10.10 than it is not an issue with the CMOS battery.  Issue: On 12G or 13G system with iDRAC firmware version 2.10.10.10 or later, the CMOS battery status in OMSA may be shown as "unknown".   Why does this occur: With IDRAC firmware 2.10.10.10 the SNMP resolution changed. So the battery status can not be resolved by OMSA 7.x correctly.   Solution: Update OMSA to version 8.1 or later.  I would recommend using the iDRAC to get a true/live status of the CMOS battery.  iDRAC -> Overview -> Hardware -> Batteries.
We just had a service call on a Dell Poweredge R720 to replace a power supply that became unusable after doing a Lifecycle Firmware Controller firmware update that went bad when updating the power slot firmware. Once the new power supply was installed, the error indicator on the console went from orange to blue and the server is operating properly.  No errors show in OMSA. However, I use the Open_Manager plugin for Nagios/Icinga to monitor my Dell servers, and it is showing an error on the R720: "Battery Probe 0 (System board CMOS battery) is Unknown reading" Is there any way I can clear this error (especially without having another service call)? Thanks for any suggestions. 
"Battery Probe 0 (System board CMOS battery) is Unknown reading"