Quick build: 18650 charger from protection/charger board, 3D printed housing and a pair of springs. Charges from USB and has a protected output (1A max) on the other end. Planning to do a second one with a switch to switch between regulated 5V (500mA) and regulated 3.3V (700mA) output https://mastodon.kampftoast.de/media/Gv-U8mvsYTdCteP3exk https://mastodon.kampftoast.de/media/nc1TEnkdB7ynJv6H8Rs
Primarily my private instance, but if you like the URL create an account. This instance is targeted at makers and software developers.