The "clock battery dead" warning will be given if the RTC has not been set
since the battery was last changed (i.e. it may indicate a new battery!). At
one time the hardware clock did not get set from NetBSD and you had to do
some magic in the firmware to set it. I think "help rtc" at the firmware
prompt gives an example (but it may be I read it somewhere else).

Id try that before replacing the battery. (on the other hand if you set the
time from the network as part of boot, it may not matter).

Mark