This reports whether the battery internal-resistance alarm, tripped by the batteryResistancePercentChange threshold, is currently active, per the description. An active status here is the plant's way of flagging a specific battery string as likely degrading before it actually fails to hold charge, meant to give the admin lead time to schedule a replacement rather than discovering the failure during the next real outage. An active(2) status paired with a batteryResistanceChange reading of 30% would justify scheduling a battery inspection soon rather than waiting for the next outage to reveal a weak string.