Quick hack for Ubuntu 12.04's https://launchpad.net/indicator-power showing remaining percentage of battery charge instead of time. This is already implemented in newer versions.

indicator-power-show-percentage.diff

diff -Naur a/data/com.canonical.indicator.power.gschema.xml.in b/data/com.canonical.indicator.power.gschema.xml.in
--- a/data/com.canonical.indicator.power.gschema.xml.in	2012-04-11 16:58:56.000000000 +0200
+++ b/data/com.canonical.indicator.power.gschema.xml.in	2013-09-09 04:29:40.921738433 +0200
@@ -5,10 +5,10 @@
     <value nick="never" value="2" />
   </enum>
   <schema gettext-domain="@GETTEXT_PACKAGE@" id="com.canonical.indicator.power" path="/com/canonical/indicator/power/">
-    <key name="show-time" type="b">
+    <key name="show-percentage" type="b">
       <default>false</default>
-      <_summary>Show time in Menu Bar</_summary>
-      <_description>Whether or not to show the time in the menu bar.</_description>
+      <_summary>Show percentage in Menu Bar</_summary>
+      <_description>Whether or not to show the percentage in the menu bar.</_description>
     </key>
     <key enum="icon-policy-enum" name="icon-policy">
       <default>"present"</default>
diff -Naur a/src/indicator-power.c b/src/indicator-power.c
--- a/src/indicator-power.c	2012-04-11 16:58:56.000000000 +0200
+++ b/src/indicator-power.c	2013-09-09 04:29:33.009602231 +0200
@@ -339,6 +339,15 @@
   gchar *short_timestring = NULL;
   gchar *detailed_timestring = NULL;
 
+  if (percentage > 0)
+    {
+      *short_details = g_strdup_printf (_("(%.0lf%%)"), percentage);
+    }
+  else
+    {
+      *short_details = g_strdup (_("(not present)"));
+    }
+
   if (time > 0)
     {
       get_timestring (time,
@@ -352,11 +361,9 @@
                                               device_name, detailed_timestring, percentage);
           *details = g_strdup_printf (_("%s (%s to charge)"),
                                       device_name, short_timestring);
-          *short_details = g_strdup_printf ("(%s)", short_timestring);
         }
       else if (state == UP_DEVICE_STATE_DISCHARGING)
         {
-          *short_details = g_strdup_printf ("%s", short_timestring);
 
           if (time > 43200) /* 12 hours */
             {
@@ -382,7 +389,6 @@
         {
           *details = g_strdup_printf (_("%s (charged)"), device_name);
           *accessible_name = g_strdup (*details);
-          *short_details = g_strdup ("");
         }
       else if (percentage > 0)
         {
@@ -391,14 +397,11 @@
           *details = g_strdup_printf (_("%s (%.0lf%%)"),
                                       device_name, percentage);
           *accessible_name = g_strdup (*details);
-          *short_details = g_strdup_printf (_("(%.0lf%%)"),
-                                            percentage);
         }
       else
         {
           *details = g_strdup_printf (_("%s (not present)"), device_name);
           *accessible_name = g_strdup (*details);
-          *short_details = g_strdup (_("(not present)"));
         }
     }
 }
@@ -671,9 +674,9 @@
       }
 
     /* options */
-    item = gtk_check_menu_item_new_with_label (_("Show Time in Menu Bar"));
+    item = gtk_check_menu_item_new_with_label (_("Show Percentage in Menu Bar"));
     g_signal_connect (item, "toggled", G_CALLBACK(option_toggled_cb), self);
-    g_settings_bind (self->settings, "show-time", item, "active", G_SETTINGS_BIND_DEFAULT);
+    g_settings_bind (self->settings, "show-percentage", item, "active", G_SETTINGS_BIND_DEFAULT);
     gtk_menu_shell_append (GTK_MENU_SHELL (self->menu), item);
 
     /* preferences */