Hello Will
The PERC should having nothing to do with the CMOS battery. You can view the voltages inside the system BIOS or via OpenManage Server Administrator in the OS.
The LCD error is reported from the hardware/system event log that is stored in the BMC. You may need to boot into the BMC BIOS(CTL E) and clear the log for the error to go away. If you have OMSA installed you can clear the log from within OMSA as well.
Thanks