Install Powerboost 1000c and Battery
The final big piece to this project is to install the battery and install the Adafruit Powerboost 1000c. The 2000 mAh battery was the only major sacrifice to this project from the PiGRRL Zero Plus, as I went down from a 2500 mAh battery to a 2000 mAh battery. However, I think you'll still be surprised about your battery life and should be able to easily get 2+ hours in between charges. Go ahead and reduce your PiTFT backlight and you'll get over 3 hours if you do it right.
step 15. install powerboost 1000c
I would recommend you place a piece of cut masking tape under the powerboost 1000c to make sure you don't have a ground issue between the powerboost and the Dpad. You'll want to clip the powerboost hole as it tends to be in the way for one of the back case screw points. Once you do that, go ahead and slip the powerboost in place tight to the PCB and solder it down.
step 16. install 2000 mah battery
Because the battery wire length is too short, plus you want to reduce the amount of clearance with the case, you will need to extend the battery wire and solder the wire directly to the powerboost 1000c. Use some heaver gauge wire and route the wires anywhere in the case to minimize pinch points when closing up the case. I routed the wires in between the Pi Zero headers. Go ahead and clip the powerboost battery terminal and directly solder the wires to the powerboost. I use a bit of masking tape to cover the powerboost to make sure no stray wires ground it out.
step 17. install power spst switch
This is a pretty simple install. Go ahead and just solder to small wires directly to the switch terminals. They depress the button and slid it into place on the case. Once you have it in place go ahead and solder the wires to the PCB. The semiflex power button will be a tight fit in the case so sanding the button is necessary. You can super glue the semiflex power button to the actual SPST switch, and even heat up a male pinout pin, stick it through the SPST button which will poke into the semiflex button, making it more difficult for the button to fall out.