Index: uspace/drv/time/cmos-rtc/cmos-regs.h
===================================================================
--- uspace/drv/time/cmos-rtc/cmos-regs.h	(revision f87ea202dcfd3bf80f585175f193d1517fdce2fd)
+++ uspace/drv/time/cmos-rtc/cmos-regs.h	(revision d8a4e79428fd53331b868a1ad778c5794ab317aa)
@@ -40,4 +40,7 @@
 #define RTC_MASK_BCD    0x04
 
+#define RTC_STATUS_D    0x0D
+#define RTC_BATTERY_OK  0x80
+
 #define RTC_UPDATE      0x0A
 #define RTC_MASK_UPDATE 0x08
Index: uspace/drv/time/cmos-rtc/cmos-rtc.c
===================================================================
--- uspace/drv/time/cmos-rtc/cmos-rtc.c	(revision f87ea202dcfd3bf80f585175f193d1517fdce2fd)
+++ uspace/drv/time/cmos-rtc/cmos-rtc.c	(revision d8a4e79428fd53331b868a1ad778c5794ab317aa)
@@ -46,4 +46,5 @@
 #include <device/hw_res.h>
 #include <devman.h>
+#include <ipc/clock_ctl.h>
 
 #include "cmos-regs.h"
@@ -82,4 +83,6 @@
 static int  rtc_register_read(rtc_t *rtc, int reg);
 static int  bcd2dec(int bcd);
+static void rtc_default_handler(ddf_fun_t *fun,
+    ipc_callid_t callid, ipc_call_t *call);
 
 
@@ -114,5 +117,5 @@
 
 	rtc_dev_ops.interfaces[CLOCK_DEV_IFACE] = &rtc_clock_dev_ops;
-	rtc_dev_ops.default_handler = NULL; /* XXX */
+	rtc_dev_ops.default_handler = &rtc_default_handler;
 }
 
@@ -387,4 +390,25 @@
 }
 
+/** Default handler for client requests not handled
+ *  by the standard interface
+ */
+static void
+rtc_default_handler(ddf_fun_t *fun, ipc_callid_t callid, ipc_call_t *call)
+{
+	sysarg_t method = IPC_GET_IMETHOD(*call);
+	rtc_t *rtc = RTC_FROM_FNODE(fun);
+	bool batt_ok;
+
+	switch (method) {
+	case CLOCK_GET_BATTERY_STATUS:
+		batt_ok = !(rtc_register_read(rtc, RTC_STATUS_D) &
+		    RTC_BATTERY_OK);
+		async_answer_1(callid, EOK, batt_ok);
+		break;
+	default:
+		async_answer_0(callid, ENOTSUP);
+	}
+}
+
 /** Open the device
  *