Basically as the title says. We have semi frequent power outages where I live. The noise machine in my daughter’s room goes out and wakes her up. If I were to buy a USB powered one, plug it into a power bank like one of those 10000ma ones you get for charging cell phones, would it have continuous power. Basically like a cheap UPS
That is definitely still a premium power bank feature. I’ve got a few newer ones that have full pd capability etc and they still don’t do both.
Lithium ion are fine in a UPS capability, they just need to be treated right. What most do is pass through to a boost buck converter. The external power passes through via a diode. When the external drops, the battery takes over instantly. Critically, when powered, the li ion is effectively disconnected.
Raspberry Pis often require this capability, so most usb UPS units mention raspberry pi, making it a useful search finder.