Ok you will need some skills and a 3d printer or access to someone with a good operational one. You need some rudimentary soldering skills and you will also need about $25 in supplies for a Chinese Solar power bank (Suggest a minimum of 20000 mah) and a small disk type QI charger available for under $5.00 also on Aliexpress.
If you shop Aliexpress carefully and look for this chassis type the 3d printed .STL file I am providing will fit providing the printer producing it is properly calibrated. I do not want to leave a link for any particular vendor because I have found a few different ones for each of the Items used.
I have waited until I have used my unit for over 3 months before setting up and posting this instructable. I wanted to prove out the print design and the performance. Since that time I have now seen similar function devices selling retail for over 100USD on many sites for units at and under 10000mah. Best part is if you loose your nerve about building this before you recieve the parts you can always use the power bank to simply power the QI charger.
Step 1: Removing the Back Cover of the Power Bank.
These units are assembled using 8 small screws. simply remove the 4 holding the back of the device on to access everything you need to work with
No other disassembly of the unit should be necessary.
Step 2: 3D Printing.
Get the 3d file at Thingiverse. and print (I use a .4 nozzle and .2 layers for most of my projects) NO raft and NO supports. I also use PLA this print. If you are using ABS, I recommend you use a 1.02 scale to account for shrinkage as I made the tolerances fairly tight so things do not move around.
Fit the completed and cooled shell on the rest of the chassis to position the screw holes which I recommend you use a 1mm drillbit and work by hand so you do not drill through to the batteries and short them.
Once that is complete you should be able to re-use the original screws (If you have 4 matching screws max length 5 mm with a head at 2.5mm they will work better but make sure the shaft of the screw is under 2mm)
Step 3: Adding the QI Charger Disk.
Disk style QI chargers are cheap and easily available for this project you simply need to open the plastic case and remove the QI unit which is generally a single unit as shown in the photos above.
All that is required from this stage is to make a direct paralell connection from the 2.1A output of the Power bank directly to the same points of the QI unit.
Place the coil in the position shown in the 2nd and 4th pictures so the printed back will fit properly.
Step 4: Place and Secure the 3d Printed Cover to the Rest of the Chassis.
Fit the back of the cover first so you can position the charging unit if necessary (I made allowances in the printed back cover for different placement needs) and test for function before securing screws.
I did confuse the polarities on the first try and got tagged by this problem so be aware.
If you see the lights on both the QI unit AND the power bank your connection should be good next try your QI device to be certain that it is working correctly.
Once that is complete and everything works it is safe to secure the new back cover with all 4 screws. (With some less expensive QI units they are thinner than the one I used so you may want to try a piece of 2 sided tape to secure so no rattling and movement occurs).
Note that if you use almost any other color than black to print the New backpiece you should be able to see the glow of the LED on the QI disk. I did not make allowances for the LEDs because I liked all arounf effect of the glow. Feel free to modify the back cover in Thingiverse and let us all know how yours came out!
The unit is essentially and functionally complete. I leave mine on the dashboard to charge and keep my cell phone off the USB charger completely. This is an off the grid option for almost anything that can be charged via QI. cellphones, tablets, GPS units LED flashlights can all be hacked to mount a QI charging coil inside.
Step 5: Bonus Option I Found VERY Helpful...
I had a couple of these cheap pads that claim to make anything stay in place on your dashboard and the charger tended to bounce around on my dash while driving so I combined the two.
I superglued and trimmed the Sticky Pad to the QI charging side of the Power bank and now there is NO sliding on the dash, Also I have found that I can use the charger by sticking it to the back of almost anything to charge OR use the USB ports.
For a $5.00 investment at the corner gas station I recommend it.
ENJOY AND INSTRUCT ON! Feed back to me and I will add on options for this instructable!