diff --git a/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java b/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java
index 56c18ba764a..b5cc6ea07b5 100644
--- a/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java
+++ b/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java
@@ -50,7 +50,7 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
     private static final int CHART_LEVEL_ARRAY_SIZE = 13;
 
     @VisibleForTesting
-    PreferenceGroup mAppListGroup;
+    PreferenceGroup mAppListPrefGroup;
 
     private Context mPrefContext;
     private BatteryChartView mBatteryChartView;
@@ -90,7 +90,7 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);
         mPrefContext = screen.getContext();
-        mAppListGroup = screen.findPreference(mPreferenceKey);
+        mAppListPrefGroup = screen.findPreference(mPreferenceKey);
     }
 
     @Override
@@ -137,8 +137,9 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
             if (entryList != null && !entryList.isEmpty()) {
                 // All battery levels are the same in the same timestamp snapshot.
                 mBatteryHistoryLevels[index] = entryList.get(0).mBatteryLevel;
-            } else {
-                Log.w(TAG, "abnormal entry list in the timestamp:" + timestamp);
+            } else if (entryList != null && entryList.isEmpty()) {
+                Log.e(TAG, "abnormal entry list in the timestamp:" +
+                    ConvertUtils.utcToLocalTime(timestamp));
             }
         }
         if (mBatteryChartView != null) {
diff --git a/src/com/android/settings/fuelgauge/ConvertUtils.java b/src/com/android/settings/fuelgauge/ConvertUtils.java
index 5c0da636595..4ddee3252ef 100644
--- a/src/com/android/settings/fuelgauge/ConvertUtils.java
+++ b/src/com/android/settings/fuelgauge/ConvertUtils.java
@@ -33,10 +33,11 @@ import java.util.TimeZone;
 /** A utility class to convert data into another types. */
 public final class ConvertUtils {
     private static final String TAG = "ConvertUtils";
-    private static final SimpleDateFormat SIMPLE_DATE_FORMAT =
-        new SimpleDateFormat("MMM dd,yyyy HH:mm:ss", Locale.ENGLISH);
+
     /** Invalid system battery consumer drain type. */
     public static final int INVALID_DRAIN_TYPE = -1;
+    /** A fake package name to represent no BatteryEntry data. */
+    public static final String FAKE_PACKAGE_NAME = "fake_package";
 
     @IntDef(prefix = {"CONSUMER_TYPE"}, value = {
         CONSUMER_TYPE_UNKNOWN,
@@ -52,6 +53,11 @@ public final class ConvertUtils {
     public static final int CONSUMER_TYPE_USER_BATTERY = 2;
     public static final int CONSUMER_TYPE_SYSTEM_BATTERY = 3;
 
+    private static String sZoneId;
+    private static SimpleDateFormat sSimpleDateFormat;
+
+    private ConvertUtils() {}
+
     /** Gets consumer type from {@link BatteryConsumer}. */
     @ConsumerType
     public static int getConsumerType(BatteryConsumer consumer) {
@@ -82,24 +88,28 @@ public final class ConvertUtils {
             int batteryHealth,
             long timestamp) {
         final ContentValues values = new ContentValues();
-        values.put("uid", Long.valueOf(entry.getUid()));
-        values.put("userId",
-            Long.valueOf(UserHandle.getUserId(entry.getUid())));
-        values.put("appLabel", entry.getLabel());
-        values.put("packageName", entry.getDefaultPackageName());
-        values.put("isHidden", Boolean.valueOf(entry.isHidden()));
+        if (entry != null && batteryUsageStats != null) {
+            values.put("uid", Long.valueOf(entry.getUid()));
+            values.put("userId",
+                Long.valueOf(UserHandle.getUserId(entry.getUid())));
+            values.put("appLabel", entry.getLabel());
+            values.put("packageName", entry.getDefaultPackageName());
+            values.put("isHidden", Boolean.valueOf(entry.isHidden()));
+            values.put("totalPower",
+                Double.valueOf(batteryUsageStats.getConsumedPower()));
+            values.put("consumePower", Double.valueOf(entry.getConsumedPower()));
+            values.put("percentOfTotal", Double.valueOf(entry.percent));
+            values.put("foregroundUsageTimeInMs",
+                Long.valueOf(entry.getTimeInForegroundMs()));
+            values.put("backgroundUsageTimeInMs",
+                Long.valueOf(entry.getTimeInBackgroundMs()));
+            values.put("drainType", getDrainType(entry.getBatteryConsumer()));
+            values.put("consumerType", getConsumerType(entry.getBatteryConsumer()));
+        } else {
+            values.put("packageName", FAKE_PACKAGE_NAME);
+        }
         values.put("timestamp", Long.valueOf(timestamp));
         values.put("zoneId", TimeZone.getDefault().getID());
-        values.put("totalPower",
-            Double.valueOf(batteryUsageStats.getConsumedPower()));
-        values.put("consumePower", Double.valueOf(entry.getConsumedPower()));
-        values.put("percentOfTotal", Double.valueOf(entry.percent));
-        values.put("foregroundUsageTimeInMs",
-            Long.valueOf(entry.getTimeInForegroundMs()));
-        values.put("backgroundUsageTimeInMs",
-            Long.valueOf(entry.getTimeInBackgroundMs()));
-        values.put("drainType", getDrainType(entry.getBatteryConsumer()));
-        values.put("consumerType", getConsumerType(entry.getBatteryConsumer()));
         values.put("batteryLevel", Integer.valueOf(batteryLevel));
         values.put("batteryStatus", Integer.valueOf(batteryStatus));
         values.put("batteryHealth", Integer.valueOf(batteryHealth));
@@ -108,8 +118,12 @@ public final class ConvertUtils {
 
     /** Converts UTC timestamp to human readable local time string. */
     public static String utcToLocalTime(long timestamp) {
-        return SIMPLE_DATE_FORMAT.format(new Date(timestamp));
+        final String currentZoneId = TimeZone.getDefault().getID();
+        if (!currentZoneId.equals(sZoneId) || sSimpleDateFormat == null) {
+            sZoneId = currentZoneId;
+            sSimpleDateFormat =
+                new SimpleDateFormat("MMM dd,yyyy HH:mm:ss", Locale.ENGLISH);
+        }
+        return sSimpleDateFormat.format(new Date(timestamp));
     }
-
-    private ConvertUtils() {}
 }
diff --git a/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java b/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java
index 70a49143985..6a5ea617b18 100644
--- a/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java
+++ b/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java
@@ -111,6 +111,29 @@ public final class ConvertUtilsTest {
             .isEqualTo(BatteryManager.BATTERY_HEALTH_COLD);
     }
 
+    @Test
+    public void testConvert_nullBatteryEntry_returnsExpectedContentValues() {
+        final ContentValues values =
+            ConvertUtils.convert(
+                /*entry=*/ null,
+                /*batteryUsageStats=*/ null,
+                /*batteryLevel=*/ 12,
+                /*batteryStatus=*/ BatteryManager.BATTERY_STATUS_FULL,
+                /*batteryHealth=*/ BatteryManager.BATTERY_HEALTH_COLD,
+                /*timestamp=*/ 10001L);
+
+        assertThat(values.getAsLong("timestamp")).isEqualTo(10001L);
+        assertThat(values.getAsString("zoneId"))
+            .isEqualTo(TimeZone.getDefault().getID());
+        assertThat(values.getAsInteger("batteryLevel")).isEqualTo(12);
+        assertThat(values.getAsInteger("batteryStatus"))
+            .isEqualTo(BatteryManager.BATTERY_STATUS_FULL);
+        assertThat(values.getAsInteger("batteryHealth"))
+            .isEqualTo(BatteryManager.BATTERY_HEALTH_COLD);
+        assertThat(values.getAsString("packageName"))
+            .isEqualTo(ConvertUtils.FAKE_PACKAGE_NAME);
+    }
+
     @Test
     public void testGetDrainType_returnsExpetcedResult() {
         final int expectedType = 3;