diff --git a/bumblebee/modules/battery.py b/bumblebee/modules/battery.py
index 2e945de..9fa4c6e 100644
--- a/bumblebee/modules/battery.py
+++ b/bumblebee/modules/battery.py
@@ -24,7 +24,7 @@ class Module(bumblebee.engine.Module):
         self._capacity = 100
 
     def capacity(self):
-        return "{:02d}%".format(self._capacity)
+        return "{:03d}%".format(self._capacity)
 
     def update(self, widgets):
         widget = widgets[0]
@@ -38,9 +38,9 @@ class Module(bumblebee.engine.Module):
 
     def state(self, widget):
         state = []
-        if self._capacity < self.parameter("critical", 10):
+        if self._capacity < int(self.parameter("critical", 10)):
             state.append("critical")
-        elif self._capacity < self.parameter("warning", 20):
+        elif self._capacity < int(self.parameter("warning", 20)):
             state.append("warning")
 
         if self._ac:
diff --git a/tests/modules/test_battery.py b/tests/modules/test_battery.py
new file mode 100644
index 0000000..da2e3cc
--- /dev/null
+++ b/tests/modules/test_battery.py
@@ -0,0 +1,64 @@
+# pylint: disable=C0103,C0111
+
+import sys
+import json
+import unittest
+import mock
+
+from contextlib import contextmanager
+
+import bumblebee.input
+from bumblebee.input import I3BarInput
+from bumblebee.modules.battery import Module
+from tests.util import MockEngine, MockConfig, assertPopen
+
+class MockOpen(object):
+    def __init__(self):
+        self._value = ""
+
+    def returns(self, value):
+        self._value = value
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, a, b, c):
+        pass
+
+    def read(self):
+        return self._value
+
+class TestBatteryModule(unittest.TestCase):
+    def setUp(self):
+        self.engine = MockEngine()
+        self.config = MockConfig()
+        self.module = Module(engine=self.engine, config={ "config": self.config })
+        for widget in self.module.widgets():
+            widget.link_module(self.module)
+
+    @mock.patch("sys.stdout")
+    def test_format(self, mock_output):
+        for widget in self.module.widgets():
+            self.assertEquals(len(widget.full_text()), len("100%"))
+
+    @mock.patch("{}.open".format("__builtin__" if sys.version_info[0] < 3 else "builtins"))
+    @mock.patch("subprocess.Popen")
+    def test_critical(self, mock_output, mock_open):
+        mock_open.return_value = MockOpen()
+        mock_open.return_value.returns("19")
+        self.config.set("battery.critical", "20")
+        self.config.set("battery.warning", "25")
+        self.module.update(self.module.widgets())
+        self.assertTrue("critical" in self.module.widgets()[0].state())
+
+    @mock.patch("{}.open".format("__builtin__" if sys.version_info[0] < 3 else "builtins"))
+    @mock.patch("subprocess.Popen")
+    def test_warning(self, mock_output, mock_open):
+        mock_open.return_value = MockOpen()
+        mock_open.return_value.returns("22")
+        self.config.set("battery.critical", "20")
+        self.config.set("battery.warning", "25")
+        self.module.update(self.module.widgets())
+        self.assertTrue("warning" in self.module.widgets()[0].state())
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4