Introduction: Solar Power Bank With Qi Wireless Charging
This little device is both a solar powered battery bank and a Qi certified wireless charging pad. On one side is a 3 watt polycrystalline solar panel capable of charging the internal batteries at about 500mAh in direct sunlight. The flip side has a Qi certified 5 watt wireless charging pad hidden underneath an acrylic panel.
Step 1: Tools and Supplies
Here's the tools and supplies you'll need to build one:
- 3D printed frame
- 3mm cut acrylic panel (145 x 145 mm)
- Adafruit solar lithium ion charger V2
- Adafruit powerboost 500 basic
- Adafruit 2.1 mm DC jack adapter cable
- Adafruit metal on/off switch with LED ring
- Anker powerport Qi certified wireless charging pad
- Uxcell 3 watt (6v) square solar panel
- 18650 lithium ion batteries and holders x2
- Micro USB cable
- Heat shrink tubing
- Panel mount LED holders x2
- 5mm LEDs x2
- 22 AWG hook up wire
- Soldering iron and solder
- Hot glue gun and gluesticks
- Two part quick set epoxy
- Multimeter (optional)
- Phillips screwdriver
- 3D printer with PLA
- Laser engraver/cutter (optional)
Step 2: The Solar Panel
The Uxcell 3 watt solar panel is one of the best deals on Amazon. It produces about 6.9v open current and 6.2v under load at about 500mAh in full sunlight.
To connect the panel to the Adafruit solar charge controller, a barrel jack adapter is needed. DO NOT connect the panel directly to the DC in pins, as it bypasses the onboard diode (which would allow the solar panel to drain the batteries in low light conditions). The positive lead on the adapter cable is labelled in white.
Step 3: The Acrylic Panel
The Qi wireless charging side of the device is made from a piece of 3mm acrylic. The dimensions are the same as the solar panel on the flip side (145 x 145 x 3mm). The charging pad is able to transfer power effectively through the acrylic, but it may not be able to transfer through additional material such as phone cases.
I used an Epilog Fusion M2 laser to etch the design and cut the acrylic to size. Cast acrylic works better than extruded for laser etching. If you don't have access to a laser cutter, acrylic can be cut using a table saw or an acrylic knife. Here's the settings I used:
- Raster: 90 speed, 65 power, 100 frequency
- Vector: 8 speed, 100 power, 100 frequency
- Auto focus off (laser height set manually)
Step 4: The 3D Printed Frame
The frame for this project is 3D printed. The dimensions are 151 x 151 x 32mm with 6mm thick walls and a 3mm wide by 5mm deep inset on each side for the solar panel and acrylic panel. The panels are both 3mm thick, so they are slightly inset into the frame, which keeps them from getting scratched when the device is flipped from one side to the other. The front of the frame has through holes for the power button and charging indicator LEDs. An .stl file of the frame is attached below.
I sliced the model in Cura 4.3, using the following settings:
- 0.38 layer height
- 60mm/s print speed
- 20% grid infill
- 0.5mm wall thickness
- skirt style bed adhesion
- support generation enabled
I printed the part on a Lulzbot Tax 6 in PLA. If you don't have a 3D printer, the .stl file can be uploaded to Treatstock.com (a 3D printing service) and printed/mailed for about $20 USD. The print takes approximately 3 hours and uses 65g of material. I used a 205C nozzle and 60C bed temperature.
Step 5: The Qi Wireless Charger
The wireless charging coil and controller for this project are from an Anker 5 watt Qi certified charging pad.
The charge controller has a micro USB input and breakout pins for power input. I chose to use a micro USB cable in this project because the connection points on the board are very small. The inductive coil is soldered to the controller board and glued to a shielding disk.
Step 6: The Solar Charge Controller Board
The voltage and current output from a solar panel fluctuates constantly depending on light conditions. While a linear charge controller (such as the TP4056) will work with a solar input, it's not very efficient. To account for the unstable input, the Adafruit solar lithium ion charging board is designed around a voltage proportional charge controller (VPCC) which stabilizes the voltage and draws maximum current from the panel. The board has an adjustable max charging rate controlled by a resistor. The default max speed is 500mAh, which is perfect for the 3 watt panel used in this project.
A large filtering capacitor is included with the board and needs to be soldered in place. Note the polarity of the capacitor (the pins on the board are labelled). In order to fit into the frame, the capacitor needs to be soldered at a 90 degree angle (parallel with the board).
The board also has an inline diode to keep the solar panel from back draining the batteries. The diode is connected to the barrel jack input, but not the DC input pins on the board. This means that a 2.1mm barrel jack cable is needed to connect a solar panel to the project.
There are JST connections and pin outs for connecting the battery and a load. In addition, there are pins for connecting external LEDs.
Step 7: The Boost Converter Board
The PowerBoost 500 basic is a DC/DC boost board. It converts the 3.0 - 4.2v input from lithium ion batteries to 5.2v at up to 1 amp. It has an easy to read pinout and connections for an external power switch. Because the power switch doesn't carry the circuit's current load, almost any switch or button can be used.
I used a micro USB cable to connect the boost board to the wireless charging pad. There are 4 wires in a USB 2.0 cable (ground, +5v, data + and data -). I soldered them to the USB output pins on the boost board (see wiring diagram step).
Step 8: The Other Components
The Adafruit solar charge controller is capable of charging a wide range of lithium ion and polymer batteries. For this project, I used two LG M29 18650 cells in parallel for a capacity of about 6000mAh. In order to keep the device balanced, I placed one battery on each side of the frame.
There are two indicator LEDs in this project: one indicates when the batteries are charging and one indicates when the charge is complete. They connect to the Adafruit solar charging board and share a + lead (see wiring diagram). The LEDs are glued into panel mounts which screw into the frame using a nut.
The Power Switch
The Adafruit SPST power switch has a built in LED with resistor. The LED pins are labelled + and -. The three additional pins are normally open (NO1), normally closed (NC1) and a ground (C1).
Step 9: The Wiring Diagram
The above wiring diagram includes all the components that need to be connected. All the connections are labelled as they are on the boards.
Step 10: Installing the Solar Panel
The first step in assembling this project is to glue the solar panel into one side of the frame. There are gaps in the rim of the frame to accommodate the raised solder points on the underside of the solar panel. I used hot glue to fix the panel in place, and then used epoxy along the edges of the panel. DO NOT use only hot glue to attach the panel as it can get hot enough to melt the glue and cause the panel to become loose.
The power switch and two panel mount LEDs are attached to the frame using the included nuts. I added a bit of glue to ensure that they stayed in place.
The batteries, powerboost board, and solar charging board are glued to the underside of the solar panel. Because its a bit tight inside the frame, test fit the components before glueing them in place to make sure everything fits. The micro USB cable from the powerboost should be about 10cm long.
Step 11: Installing the Wireless Charger
The Qi wireless charging pad and controller are glued to the underside of the acrylic panel. The charging coil should be centered on the panel with the copper coil facing towards the acrylic. I used hot glue around the outside of the shielding coil and also along the edge of the controller. DO NOT put any glue between the charging coil and the acrylic. Attach the micro USB cable to the input on the wireless charger and glue it in place on the acrylic panel.
Now the project is ready to be tested:
- Hold the project solar panel side up in direct sunlight or high intensity artificial light and make sure that the charging indicator LED lights up.
- Press the power button and make sure the LED ring lights up.
- With the power on, place a device such as a phone onto the center of the acrylic panel and make sure that it begins to charge.
If everything seems to be working, then the project is ready for final assembly.
Step 12: Final Assembly
The final step is to glue the acrylic panel into the frame. I used a thin bead of quick set epoxy along the rim, and pressed the panel into place. Because of all the wires and components, it may take some rearranging in order for the panel to sit level in the frame. That's it! You now have a fully functional solar charger for all your devices.
In testing, the device takes about 12 hours in good lighting to charge the internal batteries (about 6000mAh with the batteries I used). Using different batteries will change the device's capacity and how long it takes to charge. With full batteries the device can charge:
- A small smartphone (such as the iPhone 8) about 3 times
- A large smartphone (such as the iPhone 11 or Galaxy s10) about 2 times
- AirPods case about 10 times
If you have any questions or ideas, feel free to leave a comment at the bottom of the page. Thanks for reading, and good luck building!
Participated in the
3D Printed Contest