diff --git a/monitor/batteryIcon.py b/monitor/batteryIcon.py
index 7ee7345..089892b 100755
--- a/monitor/batteryIcon.py
+++ b/monitor/batteryIcon.py
@@ -1,29 +1,46 @@
 #!/usr/bin/env python3
 """
 Battery tray icon for Argon ONE UP on Wayland (labwc).
-Reads SOC from /sys/class/power_supply/BAT0/capacity and charging
-status from AC0/online. Updates icon every 5 seconds.
+
+Reads the battery state of charge and AC status directly from the battery
+management IC over I2C (bus 1, address 0x64) -- the same registers the
+oneUpPower kernel module uses. This means the icon works for an ordinary
+user (member of the ``i2c`` group) without sudo and without the kernel
+module being loaded. Updates every 5 seconds.
 """
 
 import sys
-import os
 import time
+
+import smbus2
 from PyQt5.QtWidgets import QApplication, QSystemTrayIcon, QMenu, QAction
 from PyQt5.QtGui import QIcon, QPainter, QColor, QFont, QPixmap
 from PyQt5.QtCore import QTimer, Qt
 
-SYSFS_BAT_CAPACITY = "/sys/class/power_supply/BAT0/capacity"
-SYSFS_BAT_STATUS = "/sys/class/power_supply/BAT0/status"
-SYSFS_AC_ONLINE = "/sys/class/power_supply/AC0/online"
+# I2C layout of the Argon ONE UP battery IC (see battery/oneUpPower.c).
+I2C_BUS = 1
+BATTERY_ADDR = 0x64
+SOC_REG = 0x04          # state of charge, percent
+CURRENT_HIGH_REG = 0x0E  # bit 7 set => running on battery (not plugged in)
 UPDATE_INTERVAL_MS = 5000
 
 
-def read_sysfs(path, default=None):
+def read_battery(bus):
+    """Return (percent, plugged_in) read over I2C, or (None, None) on error.
+
+    force=True bypasses the I2C_SLAVE busy check so the read still works if
+    the oneUpPower kernel module has claimed the address.
+    """
     try:
-        with open(path) as f:
-            return f.read().strip()
-    except (FileNotFoundError, PermissionError, OSError):
-        return default
+        soc = bus.read_byte_data(BATTERY_ADDR, SOC_REG, force=True)
+        current_high = bus.read_byte_data(BATTERY_ADDR, CURRENT_HIGH_REG,
+                                          force=True)
+    except OSError:
+        return None, None
+
+    percent = max(0, min(100, soc))
+    plugged_in = (current_high & 0x80) == 0
+    return percent, plugged_in
 
 
 def make_battery_icon(percent, charging):
@@ -97,6 +114,7 @@ class BatteryTray:
                 sys.exit(1)
             time.sleep(2)
 
+        self.bus = smbus2.SMBus(I2C_BUS)
         self.tray = QSystemTrayIcon()
 
         # Context menu
@@ -121,22 +139,16 @@ class BatteryTray:
         self.tray.show()
 
     def update(self):
-        cap_str = read_sysfs(SYSFS_BAT_CAPACITY)
-        status = read_sysfs(SYSFS_BAT_STATUS, "Unknown")
-        ac_str = read_sysfs(SYSFS_AC_ONLINE, "0")
+        percent, plugged_in = read_battery(self.bus)
 
-        if cap_str is not None:
-            try:
-                percent = int(cap_str)
-            except ValueError:
-                percent = 0
-            charging = (ac_str == "1" or status == "Charging")
+        if percent is not None:
+            charging = plugged_in and percent <= 95
             icon = make_battery_icon(percent, charging)
             self.tray.setIcon(icon)
 
             if charging:
                 state = "Charging"
-            elif ac_str == "1":
+            elif plugged_in:
                 state = "On AC"
             else:
                 state = "Discharging"
@@ -144,11 +156,11 @@ class BatteryTray:
             self.tray.setToolTip(tooltip)
             self.status_action.setText(tooltip)
         else:
-            # No battery sysfs - module not loaded
+            # I2C read failed - IC not reachable
             icon = make_battery_icon(0, False)
             self.tray.setIcon(icon)
-            self.tray.setToolTip("Battery: N/A (module not loaded?)")
-            self.status_action.setText("Battery: N/A (module not loaded?)")
+            self.tray.setToolTip("Battery: N/A (I2C read failed)")
+            self.status_action.setText("Battery: N/A (I2C read failed)")
 
     def run(self):
         return self.app.exec()