How does Phone Link know my iPhone's battery level?

You’re seeing Phone Link report the iPhone’s charge even though Bluetooth is often associated with audio. Microsoft requires Bluetooth Low Energy for the iPhone connection and lists battery and connectivity status as supported information. Bluetooth LE can exchange values through GATT services and characteristics; Microsoft also documents a standard Battery Service and Battery Level characteristic for Windows-capable Bluetooth devices. In practical terms, Phone Link receives a battery value through the paired Bluetooth relationship and displays it; it is not estimating 95% from signal strength. To verify the path, turn Bluetooth off temporarily on either device and watch the status stop updating, then reconnect and confirm it refreshes. Keep Windows, Phone Link, and iOS current. If the value becomes stale, remove the pairing on both devices and pair again. Microsoft does not document the exact Apple-side characteristic Phone Link uses, so a more specific claim would be speculation.