diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index 304feb82021..0aaf930e112 100755
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -443,7 +443,7 @@
     <!-- Battery usage chart view component -->
     <dimen name="chartview_divider_width">1dp</dimen>
     <dimen name="chartview_divider_height">4dp</dimen>
-    <dimen name="chartview_trapezoid_radius">2dp</dimen>
+    <dimen name="chartview_trapezoid_radius">3dp</dimen>
     <dimen name="chartview_trapezoid_margin_start">1dp</dimen>
     <dimen name="chartview_trapezoid_margin_bottom">2dp</dimen>
 </resources>
diff --git a/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java b/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java
index 4cafbc7b693..7131f28eb20 100644
--- a/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java
+++ b/src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java
@@ -317,6 +317,7 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
         }
         int prefIndex = mAppListPrefGroup.getPreferenceCount();
         for (BatteryDiffEntry entry : entries) {
+            boolean isAdded = false;
             final String appLabel = entry.getAppLabel();
             final Drawable appIcon = entry.getAppIcon();
             if (TextUtils.isEmpty(appLabel) || appIcon == null) {
@@ -324,8 +325,13 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
                 continue;
             }
             final String prefKey = entry.mBatteryHistEntry.getKey();
-            PowerGaugePreference pref =
-                (PowerGaugePreference) mPreferenceCache.get(prefKey);
+            PowerGaugePreference pref = mAppListPrefGroup.findPreference(prefKey);
+            if (pref != null) {
+                isAdded = true;
+                Log.w(TAG, "preference should be removed for\n" + entry);
+            } else {
+                pref = (PowerGaugePreference) mPreferenceCache.get(prefKey);
+            }
             // Creates new innstance if cached preference is not found.
             if (pref == null) {
                 pref = new PowerGaugePreference(mPrefContext);
@@ -340,7 +346,9 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
             // Sets the BatteryDiffEntry to preference for launching detailed page.
             pref.setBatteryDiffEntry(entry);
             setPreferenceSummary(pref, entry);
-            mAppListPrefGroup.addPreference(pref);
+            if (!isAdded) {
+                mAppListPrefGroup.addPreference(pref);
+            }
             prefIndex++;
         }
     }
diff --git a/src/com/android/settings/fuelgauge/BatteryChartView.java b/src/com/android/settings/fuelgauge/BatteryChartView.java
index 26eb3e40c55..f970072cb94 100644
--- a/src/com/android/settings/fuelgauge/BatteryChartView.java
+++ b/src/com/android/settings/fuelgauge/BatteryChartView.java
@@ -97,8 +97,18 @@ public class BatteryChartView extends AppCompatImageView implements View.OnClick
     public void setLevels(int[] levels) {
         // We should provide trapezoid count + 1 data to draw all trapezoids.
         mLevels = levels.length == mTrapezoidCount + 1 ? levels : null;
-        setClickable(mLevels != null);
+        setClickable(false);
         invalidate();
+        if (mLevels == null) {
+            return;
+        }
+        // Sets the chart is clickable if there is at least one valid item in it.
+        for (int index = 0; index < mLevels.length; index++) {
+            if (mLevels[index] != 0) {
+                setClickable(true);
+                break;
+            }
+        }
     }
 
     /** Sets the selected group index to draw highlight effect. */
diff --git a/src/com/android/settings/fuelgauge/ConvertUtils.java b/src/com/android/settings/fuelgauge/ConvertUtils.java
index 30982da6c8d..2e8726e38ab 100644
--- a/src/com/android/settings/fuelgauge/ConvertUtils.java
+++ b/src/com/android/settings/fuelgauge/ConvertUtils.java
@@ -71,6 +71,7 @@ public final class ConvertUtils {
 
     private static String sZoneId;
     private static SimpleDateFormat sSimpleDateFormat;
+    private static SimpleDateFormat sSimpleDateFormatForHour;
 
     private ConvertUtils() {}
 
@@ -139,10 +140,27 @@ public final class ConvertUtils {
             sZoneId = currentZoneId;
             sSimpleDateFormat =
                 new SimpleDateFormat("MMM dd,yyyy HH:mm:ss", Locale.ENGLISH);
+            sSimpleDateFormatForHour = null;
         }
         return sSimpleDateFormat.format(new Date(timestamp));
     }
 
+    /** Converts UTC timestamp to local time hour data. */
+    public static int utcToLocalTimeHour(long timestamp) {
+        final String currentZoneId = TimeZone.getDefault().getID();
+        if (!currentZoneId.equals(sZoneId) || sSimpleDateFormatForHour == null) {
+            sZoneId = currentZoneId;
+            sSimpleDateFormat = null;
+            sSimpleDateFormatForHour = new SimpleDateFormat("HH", Locale.ENGLISH);
+        }
+        try {
+            return Integer.parseInt(
+                sSimpleDateFormatForHour.format(new Date(timestamp)));
+        } catch (NumberFormatException e) {
+            return Integer.MIN_VALUE;
+        }
+    }
+
     /** Gets indexed battery usage data for each corresponding time slot. */
     public static Map<Integer, List<BatteryDiffEntry>> getIndexedUsageMap(
             final Context context,
diff --git a/tests/robotests/src/com/android/settings/fuelgauge/BatteryChartPreferenceControllerTest.java b/tests/robotests/src/com/android/settings/fuelgauge/BatteryChartPreferenceControllerTest.java
index a70a109330c..9f0ffb01b10 100644
--- a/tests/robotests/src/com/android/settings/fuelgauge/BatteryChartPreferenceControllerTest.java
+++ b/tests/robotests/src/com/android/settings/fuelgauge/BatteryChartPreferenceControllerTest.java
@@ -57,6 +57,8 @@ import java.util.Map;
 
 @RunWith(RobolectricTestRunner.class)
 public final class BatteryChartPreferenceControllerTest {
+    private static final String PREF_KEY = "pref_key";
+    private static final String PREF_SUMMARY = "fake preference summary";
 
     @Mock private InstrumentedPreferenceFragment mFragment;
     @Mock private SettingsActivity mSettingsActivity;
@@ -120,10 +122,9 @@ public final class BatteryChartPreferenceControllerTest {
 
     @Test
     public void testOnDestroy_clearPreferenceCache() {
-        final String prefKey = "preference fake key";
         // Ensures the testing environment is correct.
         mBatteryChartPreferenceController.mPreferenceCache.put(
-            prefKey, mPowerGaugePreference);
+            PREF_KEY, mPowerGaugePreference);
         assertThat(mBatteryChartPreferenceController.mPreferenceCache).hasSize(1);
 
         mBatteryChartPreferenceController.onDestroy();
@@ -231,17 +232,16 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testRemoveAndCacheAllPrefs_buildCacheAndRemoveAllPreference() {
         final int trapezoidIndex = 1;
-        final String prefKey = "preference fake key";
         doReturn(1).when(mAppListGroup).getPreferenceCount();
         doReturn(mPowerGaugePreference).when(mAppListGroup).getPreference(0);
-        doReturn(prefKey).when(mPowerGaugePreference).getKey();
+        doReturn(PREF_KEY).when(mPowerGaugePreference).getKey();
         // Ensures the testing data is correct.
         assertThat(mBatteryChartPreferenceController.mPreferenceCache).isEmpty();
 
         mBatteryChartPreferenceController.refreshUi(
             trapezoidIndex, /*isForce=*/ true);
 
-        assertThat(mBatteryChartPreferenceController.mPreferenceCache.get(prefKey))
+        assertThat(mBatteryChartPreferenceController.mPreferenceCache.get(PREF_KEY))
             .isEqualTo(mPowerGaugePreference);
         verify(mAppListGroup).removeAll();
     }
@@ -255,12 +255,12 @@ public final class BatteryChartPreferenceControllerTest {
 
     @Test
     public void testAddPreferenceToScreen_addPreferenceIntoScreen() {
-        final String prefKey = "preference fake key";
         final String appLabel = "fake app label";
         doReturn(1).when(mAppListGroup).getPreferenceCount();
         doReturn(mDrawable).when(mBatteryDiffEntry).getAppIcon();
         doReturn(appLabel).when(mBatteryDiffEntry).getAppLabel();
-        doReturn(prefKey).when(mBatteryHistEntry).getKey();
+        doReturn(PREF_KEY).when(mBatteryHistEntry).getKey();
+        doReturn(null).when(mAppListGroup).findPreference(PREF_KEY);
 
         mBatteryChartPreferenceController.addPreferenceToScreen(
             Arrays.asList(mBatteryDiffEntry));
@@ -268,11 +268,11 @@ public final class BatteryChartPreferenceControllerTest {
         // Verifies the preference cache.
         final PowerGaugePreference pref =
             (PowerGaugePreference) mBatteryChartPreferenceController.mPreferenceCache
-                .get(prefKey);
+                .get(PREF_KEY);
         assertThat(pref).isNotNull();
         // Verifies the added preference configuration.
         verify(mAppListGroup).addPreference(pref);
-        assertThat(pref.getKey()).isEqualTo(prefKey);
+        assertThat(pref.getKey()).isEqualTo(PREF_KEY);
         assertThat(pref.getTitle()).isEqualTo(appLabel);
         assertThat(pref.getIcon()).isEqualTo(mDrawable);
         assertThat(pref.getOrder()).isEqualTo(1);
@@ -280,6 +280,21 @@ public final class BatteryChartPreferenceControllerTest {
         assertThat(pref.isSingleLineTitle()).isTrue();
     }
 
+    @Test
+    public void testAddPreferenceToScreen_alreadyInScreen_notAddPreferenceAgain() {
+        final String appLabel = "fake app label";
+        doReturn(1).when(mAppListGroup).getPreferenceCount();
+        doReturn(mDrawable).when(mBatteryDiffEntry).getAppIcon();
+        doReturn(appLabel).when(mBatteryDiffEntry).getAppLabel();
+        doReturn(PREF_KEY).when(mBatteryHistEntry).getKey();
+        doReturn(mPowerGaugePreference).when(mAppListGroup).findPreference(PREF_KEY);
+
+        mBatteryChartPreferenceController.addPreferenceToScreen(
+            Arrays.asList(mBatteryDiffEntry));
+
+        verify(mAppListGroup, never()).addPreference(any());
+    }
+
     @Test
     public void testHandlePreferenceTreeClick_notPowerGaugePreference_returnFalse() {
         assertThat(mBatteryChartPreferenceController.handlePreferenceTreeClick(mAppListGroup))
@@ -310,7 +325,7 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testSetPreferenceSummary_setNullContentIfTotalUsageTimeIsZero() {
         final PowerGaugePreference pref = new PowerGaugePreference(mContext);
-        pref.setSummary("fake preference summary");
+        pref.setSummary(PREF_SUMMARY);
 
         mBatteryChartPreferenceController.setPreferenceSummary(
             pref, createBatteryDiffEntry(
@@ -322,7 +337,7 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testSetPreferenceSummary_setBackgroundUsageTimeOnly() {
         final PowerGaugePreference pref = new PowerGaugePreference(mContext);
-        pref.setSummary("fake preference summary");
+        pref.setSummary(PREF_SUMMARY);
 
         mBatteryChartPreferenceController.setPreferenceSummary(
             pref, createBatteryDiffEntry(
@@ -334,7 +349,7 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testSetPreferenceSummary_setTotalUsageTimeLessThanAMinute() {
         final PowerGaugePreference pref = new PowerGaugePreference(mContext);
-        pref.setSummary("fake preference summary");
+        pref.setSummary(PREF_SUMMARY);
 
         mBatteryChartPreferenceController.setPreferenceSummary(
             pref, createBatteryDiffEntry(
@@ -346,7 +361,7 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testSetPreferenceSummary_setTotalTimeIfBackgroundTimeLessThanAMinute() {
         final PowerGaugePreference pref = new PowerGaugePreference(mContext);
-        pref.setSummary("fake preference summary");
+        pref.setSummary(PREF_SUMMARY);
 
         mBatteryChartPreferenceController.setPreferenceSummary(
             pref, createBatteryDiffEntry(
@@ -358,7 +373,7 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testSetPreferenceSummary_setTotalAndBackgroundUsageTime() {
         final PowerGaugePreference pref = new PowerGaugePreference(mContext);
-        pref.setSummary("fake preference summary");
+        pref.setSummary(PREF_SUMMARY);
 
         mBatteryChartPreferenceController.setPreferenceSummary(
             pref, createBatteryDiffEntry(
@@ -370,7 +385,7 @@ public final class BatteryChartPreferenceControllerTest {
     @Test
     public void testSetPreferenceSummary_notAllowShownPackage_setSummayAsNull() {
         final PowerGaugePreference pref = new PowerGaugePreference(mContext);
-        pref.setSummary("fake preference summary");
+        pref.setSummary(PREF_SUMMARY);
         final BatteryDiffEntry batteryDiffEntry =
             spy(createBatteryDiffEntry(
                 /*foregroundUsageTimeInMs=*/ DateUtils.MINUTE_IN_MILLIS,
@@ -436,33 +451,31 @@ public final class BatteryChartPreferenceControllerTest {
 
     @Test
     public void testOnExpand_expandedIsTrue_addSystemEntriesToPreferenceGroup() {
-        final String prefKey = "preference_key";
         doReturn(1).when(mAppListGroup).getPreferenceCount();
         mBatteryChartPreferenceController.mSystemEntries.add(mBatteryDiffEntry);
         doReturn("label").when(mBatteryDiffEntry).getAppLabel();
         doReturn(mDrawable).when(mBatteryDiffEntry).getAppIcon();
-        doReturn(prefKey).when(mBatteryHistEntry).getKey();
+        doReturn(PREF_KEY).when(mBatteryHistEntry).getKey();
 
         mBatteryChartPreferenceController.onExpand(/*isExpanded=*/ true);
 
         final ArgumentCaptor<Preference> captor = ArgumentCaptor.forClass(Preference.class);
         verify(mAppListGroup).addPreference(captor.capture());
         // Verifies the added preference.
-        assertThat(captor.getValue().getKey()).isEqualTo(prefKey);
+        assertThat(captor.getValue().getKey()).isEqualTo(PREF_KEY);
     }
 
     @Test
     public void testOnExpand_expandedIsFalse_removeSystemEntriesFromPreferenceGroup() {
-        final String prefKey = "preference_key";
-        doReturn(prefKey).when(mBatteryHistEntry).getKey();
-        doReturn(mPowerGaugePreference).when(mAppListGroup).findPreference(prefKey);
+        doReturn(PREF_KEY).when(mBatteryHistEntry).getKey();
+        doReturn(mPowerGaugePreference).when(mAppListGroup).findPreference(PREF_KEY);
         mBatteryChartPreferenceController.mSystemEntries.add(mBatteryDiffEntry);
         // Verifies the cache is empty first.
         assertThat(mBatteryChartPreferenceController.mPreferenceCache).isEmpty();
 
         mBatteryChartPreferenceController.onExpand(/*isExpanded=*/ false);
 
-        verify(mAppListGroup).findPreference(prefKey);
+        verify(mAppListGroup).findPreference(PREF_KEY);
         verify(mAppListGroup).removePreference(mPowerGaugePreference);
         assertThat(mBatteryChartPreferenceController.mPreferenceCache).hasSize(1);
     }