You can check the charge status while the collar is charging. Make sure the collar is placed in the charge base and connected to AC power. Press and immediately release Power Button. The LED Status Indicator will turn on for about thirty seconds, then turn off. If the LED indicator is flashing green the system is charging. If the LED is solid green the system is fully charged.
If the collar is not connected to the charger then use the app to connect to the collar and check charge status. Open the app, go to the Dogs screen, then tap Connect to Manage. The charge status will be shown on the screen.