The average charging time from empty to full is about 10 hours. During the charging process the LED flashes. When the Nuki Power Pack is fully charged the LED turns off.
Please note that the Power Pack reaches the full charging capacity after 2-3 charging processes.
The charging process is only started when the charge level has dropped below 75%. This is to protect the battery.
At a power level of 20% Nuki will notify you via the Nuki app and directly on the Smart Lock. So there is enough time to replace your batteries of your Smart Lock. In case you are not able to change the batteries or to charge the battery of your Nuki Power Pack in time, you can still use your existing, mechanical key.