Hello. I used to have a uninterruptable power supply(UPS) connected to all my printers so I wouldn't loose power. Then one day I lost power and the 3d printer stayed on. And so came the realization of reality. When the power goes out we do not need the printer to stay on. Hell if we have stored power and we loose power whatever we have stored could very probably be used for something of greater importance. We just need the printer to raise Z a few MM so the nozzle doesn't melt the print and to remember where it was. And so the power loss modules are really just a capacitor bank that stores just enough power to facilitate raising Z and remembering where in the Gcode the printer was in the moment the power went out.

I have one of these on each of my printers. They make them in 2 flavors. 12v and 24v. The 24v has 2 rows of capacitors whereas the 12v has just one row of caps. Here is a link to the 24v model from the manufacturer's website: BTT UPS 24V V1.0 Resume Printing While Power Off Module (biqu.equipment)

Once you get it and aside from the info you have there is a short but very helpful setup walkthrough right here: How to install BigtreeTech Mini Ups - YouTube

And there is one last important thing you need to know about. Because this is a capacitor bank we attach to the supply voltage wire feeding the mainboard once installed every time you turn off the power the power stays on for a few seconds and then slowly turns off as the capacitors loose their juice. I can't stand this so I use DPST power switches and instead of having the switch break the line and neutral coming in from the wall I have the DPST power switch interrupting just the line to the power supply from the wall and also the +24v wire feed to the BTT UPS 24v. And the red light on the UPS stays on for a while because the caps are charged but there is no load connected. But the printer shuts right off when the switch is turned off.

Here is a picture of one of my printers' power switch..



And here are the connections made for the functionality I spoke of..