How can I tell when an unpaired gotenna mesh device is fully charged?

Documentation says that when charging, the red LED will go out when the device is fully charged. But my devices (with the most recent firmware) stay full red even if the app with a paired unit says 100% charged? So how can I tell when a device that is not paired is fully charged?

When did they do an update and how do you perform an update?

Hello, normally a fully charged device’s LED will turn from red to blue. If you continue to charge the device past this point, the battery will discharge by a few percent and recharge to prevent overcharging. During this discharge period, the LED will turn red again.