For ~$20, you can turn your Ryobi 18V battery into a power engine for your IoT projects or a mega battery charger that would last you many days out in the camp or where ever you choose to be without AC power.

Here is the link to the 3D-printed power clip: ~$5
https://www.thingiverse.com/thing:1194867

12V Car Lighter Socket/Plug: ~$6

24V-tolerant USB Car charger: ~$9