Poweredge 800 BMC CMOS battery failure Event 1154

I have a Poweredge 800 server. The amber light on the front of the case is flashing amber. Server Administrator reports a BMC CMOS battery failure and Windows event log shows Event 1154. I have replaced the CMOS battery on the mainboard but the failure is still indicated. Apparently the alert is referring to a different battery but I can't find one on the board. Are the BMC and associated battery built in to the mainboard? We don't use out of band communication with this server. Is a BMC problem something we need to worry about if we don't try to remotely access the server outside Windows?