A very simple battery pack for 6x18650 cells in parallel.

Used this model as a base for the battery holder:

https://www.printables.com/model/13257-18650-battery-holder

Used this "IP5328P Dual USB 18650 Battery Charger" from Aliexpress:

https://www.aliexpress.com/item/1005004177447985.html

The circuit is mounted upside down.

Also made a very simple enclosure.