Using the top half of the case now…
The same notch-and-pivot motion holds the battery. It may be a little loose right now…that’s okay, the other half of the case will secure it…do not add any tape or glue.
Using scissors or a straightedge and blade, cut a 50mm square piece from the filter foam. You can borrow the separator piece for a moment as a template.
The foam then fits into the remaining void in the top case piece.
If any of the protrusions break off during this step (especially the long narrow one supporting the switch), they can be glued back in place using 5-minute epoxy. Wait until its set firm before trying again.
Once the case closes correctly, drop two #4-40 nuts into the hexagonal pits on the back of the case, then catch these with two #4-40 x 1/2 inch screws inserted from the front.
If printed with a translucent or light-colored filament, you can see the PowerBoost status LEDs:
A red LED means the battery is very low — below 3.2 Volts.
The nice thing about lithium-polymer cells is that you can top them off any time, low battery or not. Plug in a USB microB cable to a phone- or tablet-charging wall supply, or a powered USB hub. You’ll see a yellow LED while charging, and a green LED when full. A full charge may take about an hour.
You can use the fan while plugged into USB, but it may charge a little more slowly.
With a full charge, the fan will run at least an hour, perhaps close to 90 minutes before the battery cuts out.