Ever been on a long hike on a warm day just to have it ruined by your phone going dead? Well, now your problem is solved with a solar powered phone charging backpack!

The instructable shows you how to install solar panels into your backpack in a seamless way.

Step 1: Materials and Tools

Materials

(1) backpack. There are 2 requirements when choosing a good backpack for this project: room to install your solar panels and a pocket to store your cell phone. The Drifter square backpack is perfect for this project.
(1) portable solar panel with usb output. The 5w from Brown Dog Gadgets works great!
Plenty of felt. It should be enough to provide backing for your solar panel and
(1) role of Velcro
Plenty of thread. Be bold and have it accent your solar panels or have it match the color of your backpack. It is up to you!

Tools

Scissors. Fabric or brand new scissor work best.
Stitching Needle.
Utility knife.
Fabric pencil or crayon.
Hot glue gun.
Freshly made fruit smoothie. This is to keep you hydrated and energized while you work.
1 extra hand (optional). This will definitely help and you can also give it high fives after each step!

Step 2: Cut Your Felt Backing

Measure your felt backing. This backing should be enough to attach your solar panel to the backpack. For this bag, 11 inches wide and 16 inches high was perfect.

Mark your measurements with a felt pencil and cut with fabric scissors.

Then give that extra hand a high five!

Step 3: Prepare Your Solar Panel (OPTIONAL)

If you backpack is large or if your solar panel is flexible, you may be able to skip this step. But to provide maximum flexibility, strip the excess backing from the solar panel. Be very careful of the any wiring and other important connections.

Note: After doing this, I actually think I wouldn't recommend it. There is too much opportunity to ruin you solar panel. It will, most likely, void any warranty. This should only be done if it is needed and do this at your own risk.

Step 4: Attach Solar Panel to Backing

Using hot glue, attach the solar panel to the felt backing. Attach one panel at a time and make sure that there is enough room for velcro on all sides of each panel.

Step 5: Add Velcro to Backing

Add the soft side of the velcro on all exposed felt. Make sure to get it from edge to edge and in between the panels. Also get as close to the usb output as possible.

Step 6: Add Velcro to Backpack (part 1)

For each soft velcro strip on the felt backing, cut a strip of corresponding rough side of the velcro. You can make sure you have all the right pieces by attaching them as you cut them.

Then turn the backpack inside out and take one of the rough edge pieces and attach it to the edge of the backpack.

Once you've attached that piece, attach the felt to the backpack aligning it with that piece. This will be your guide for attaching the rest of the velcro in the next step.

Step 7: Add Velcro to Backpack (part 2)

Lift the felt backing and expose the sticky part of the velcro for all of the velcro in between the panels. Stick them to the bag using your felt backing as a guide.

Then attach the last edge of velcro which is large strip perpendicular to the panels. Finally attach the felt to this piece.

Step 8: Cut Port Holes Into Backpack

Using a fabric pencil, trace around each panel to create a the openings that you will be cutting.

PRO TIP: Measure twice and cut once. My initial markings were by feel, but I then pulled the felt off the back pack and verified my markings to be in the right place by measuring it with a tape measure. Make sure you do this. You don't want to make the holes too big!

Remove your felt backing with your panels and begin to cut out your port holes. Start in the middle with a utility knife and then use scissors. Start small and check your sizes often.

Step 9: Reattach Solar Panels to Back Pack

Once you've cut out your port holes, reattach your solar panels to the back pack.

Step 10: Make the Phone Pocket

Make a small incision in one of the pockets. Attach the phone charger cord to the usb on the solar panel an feed the other end through the small incision.

Step 11: Stitch the Port Holes

Turn the backpack right side out and stitch the edges of the port holes using a needle and thread.

PRO TIP: Take a break! If you've been neglecting your smoothie, spend time inspecting your awesome work!

Step 12: Test It Out!

Take you bag outside and test it out. Now it is time to go for a walk and charge your phone!

For more accurate testing, you can use a device like this Charge Doctor for measuring the current and voltage output of the solar panel. The more perpendicular the panel is to the sun's light rays, the higher the power output!

Also, you can track the sun's path with augmented reality app like this one to find the optimal location for solar panel placement and make sure that shadows from trees don't block you:

http://www.sunsurveyor.com