Sun Fire T2000 SC Battery Voltage warning is not shown neither in showfaults nor in showlogs output. As the result of this, there is no alarms logged in the syslog as well.
Surprisingly, showenvironment command shows "SC/BAT/V_BAT WARNING"!!!
Does that error have any sort of a time stamp associated with it?
(I'm going to guess "No".)
Keep in mind that you are asking about a battery for the system's SC and not the battery for the systemboard -- which is another beast altogether.
Clear the error and forget it occurred.
It may have been logged a long time ago when the system was fresh out-of-the-box and the SC lost mains power. You can glance, perhaps once per month, to see if the event ever repeats.
If you can afford some downtime to get the box to a powered-down state, you could remove the SC card and replace or reseat the battery that is on it. The T2000 documentation is here: