3S Power Bank - 29.7Ah

thingiverse

I needed a reliable power source for my Android tablet in the field, so I built one myself. 3 - 18650 9900mAh batteries provide me with 29.7Ah of backup power. A budget-friendly charger controller for $2.50 with 1A and 2.1A outputs meets my needs perfectly. Solder the 3 batteries together in parallel using a wiring channel located at the base for the negative lead. The circuit comes to life on the last solder joint, and it illuminates as a sign that everything is wired correctly. A long press of the button turns on the display and the "flashlight", while a quick double press of the button shuts off the "flashlight". I used the middle-sized button in my tablet, but you can use either size; I just happened to choose the one that fits best. Make sure the button moves freely in its hole and sits snugly in its recess.