Hi Russell
The Batteries information will only be shown when your Apple Watch is connected to your iPhone via Bluetooth.
For the best performance from your watch, keep both Bluetooth and Wi-Fi permanently enabled on your iPhone:
- Phone: Settings > Bluetooth - on.
- Phone: Settings > Wi-Fi - on.
Check also that your Apple Watch is not in Airplane Mode:
- When viewing the time on your watch, swipe up on your watch face > swipe left / right to the Settings Glance > disable Airplane Mode if it is enabled.
When configured in this way, you should see the Batteries information in the Today section of Notification Centre on your iPhone.