a try?

src/battery.c

@@ -5,19 +5,54 @@
 #include <hidsdi.h>
 #include <stdio.h>
 
+#define RAZER_REPORT_ID_BATTERY 0x03
+#define RAZER_BATTERY_REPORT_SIZE 64
+#define RAZER_BATTERY_LEVEL_INDEX 3
+#define RAZER_CHARGING_STATUS_INDEX 4
+
+/*****************************************************************************
+ *
+ *                       This code doesn't work.
+ *
+ *************************************************************************** */
+
 int get_battery_level(const char *device_path, bool *is_charging) {
-  HANDLE hDevice =
+  HANDLE hDevice = CreateFile(device_path, GENERIC_READ | GENERIC_WRITE,
-      CreateFile(device_path, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
+                              FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
-                 NULL, OPEN_EXISTING, 0, NULL);
+                              OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
   if (hDevice == INVALID_HANDLE_VALUE) {
     fprintf_s(stderr, "Failed to open device.\n");
 
     return -1;
   }
 
-  int batteryLevel;
+  unsigned char report[RAZER_BATTERY_REPORT_SIZE] = {0};
+  DWORD bytesReturned;
 
-  // TODO
+  // Prepare the report to request battery information
+  report[0] = RAZER_REPORT_ID_BATTERY;
+
+  // Send the report
+  if (!HidD_SetFeature(hDevice, report, RAZER_BATTERY_REPORT_SIZE)) {
+    fprintf_s(stderr, "Failed to send report to device.\n");
+
+    CloseHandle(hDevice);
+    return -1;
+  }
+
+  // Read the response
+  if (!HidD_GetFeature(hDevice, report, RAZER_BATTERY_REPORT_SIZE)) {
+    fprintf_s(stderr, "Failed to read report from device.\n");
+
+    CloseHandle(hDevice);
+    return -1;
+  }
+
+  // Extract battery level
+  int batteryLevel = report[RAZER_BATTERY_LEVEL_INDEX];
+
+  // Extract charging status
+  *is_charging = (report[RAZER_CHARGING_STATUS_INDEX] != 0);
 
   CloseHandle(hDevice);
   return batteryLevel;