I have made a standard USB-PD powerbank into an ACTUAL UPS by connecting a small board that allows you to manually select the voltage of the output. By selectin

I have made a standard USB-PD powerbank into an ACTUAL UPS by connecting a small board that allows you to manually select the voltage of the output. By selecting 12V you can then wire up any 12V device of reasonable power (say a wireless router) to the USB powerbank. There is no loss converting to and from AC and the power bank internals still handle all the complicated charging and whatnot. All the little IO board does is request a specific voltage (in the same way that any device with PD will negotiate) and keep it there. I also found a small fanless inverter that I wired to this setup which gave me a tiny and completely silent AC power device. Super small, super portable. Easily powers a few LED bulbs or strings.