I have a bunch of different Ryobi 18V Power tools and an assortment of One+ Lithium batteries. I thought it would be great to make use of these batteries for other things. I decided to make a Power station that could charge USB devices and run 12V cigarette lighter socket devices. I also added an LED light for emergencies. It has room for 3 different sockets. I currently use one that has two 2.4A USB connections, another that has a QC 3.0 and Type C connectors, and a third that is a 12V cigarette light socket.

I got inspiration from https://www.thingiverse.com/thing:2467237

This can easily charge your cell phone or run a laptop
You could use the 12V socket to run a small AC inverter or a CPAP machine when you are camping or traveling

Here is a movie of the build process: https://youtu.be/p9G_shkDBt4
An earlier prototype can be viewed at: https://youtu.be/rdvFLKf1roE

I just tested all my Ryobi tool batteries for capacity.

Ryobi 9Ah/162Wh P194 got 133Wh
Ryobi 6Ah/108Wh P193 got 98 Wh
Vanon 6Ah / 108Wh got ONLY 58 Wh
Ryobi 4Ah/74 Wh P108 got 55Wh
Ryobi 3Ah/54 Wh P191 got 42Wh
Ryobi 1.5Ah/28 Wh P107 got 19Wh
Ryobi ?Ah/24 Wh P102 got 13Wh

I had nice short Amazon links here of the parts I used, but Thingiverse edited my summary and changed all the links so they could make money off of them. Check out the models on https://www.prusaprinters.org/prints/22019-diy-ryobi-18v-one-powerstation
Sorry for the inconvenience :-(

Revision History (see photo):
prototype -- tested battery connection
prototype V1 -- functional test of DC-DC converter, USB ports / 12V cigarette socket
prototype V2 - New tower shape with 3 socket holes
prototype V2a - added handle strap
prototype V2b - added second switch to turn all power off, thickened strap holder
prototype V2c - lengthened DC converter opening, beveled edges, widened strap holder opening
future improvements: label switches with icons, put switch notches in model

Here is a link to the CAD STEP file (I couldn't get thingiverse to upload it):
http://howmuchsnow.com/batterypowersystem/ryobipowerstationV3c.stp

https://www.prusaprinters.org/prints/22019-diy-ryobi-18v-one-powerstation