Press the button for 3 seconds to start trickle charge mode. Devices with low power consumption can thus be charged over a longer period of time without overcharging or without the power bank switching off first (and then no longer charging). However, the charging power is lower. See also the comment by Liceo!

This function is intended for "low power" devices such as a smart watch or other small items. These devices draw little power and this function is intended to prevent the power bank from switching off accidentally.

Thanks for the clarifying comments, Liceo and alainrichard, I hadn't found any information on this anywhere either.

...that's exactly what I've been asking myself and I haven't been able to figure it out yet... even ChatGPT hasn't been able to help yet....

Everything works by itself. Plug it in and it charges.

This means that you press the button for 3 seconds and then you will see the charge level in per cent on the display of the power bank.