Here are some constraints I made so that it could fit my ideal use for this project:
1. Small enough to fit into a pack or purse for easy carrying.
2. Multiple charging options for storing power. You don't always have access to an electrical outlet. Utilizing several sources of power would mean greater functionality.
3. Multiple power output sources for charging off the battery.
4. Sturdy construction with good protection of the inner electronics.
5. Large battery for extended charging or multiple charges of a device.
6. A $60 budget. Most power banks with a high capacity battery and/or secondary charging methods fall within this budget.
This device has applications for day-to-day power needs, camping, hiking, traveling, storm shelters/power outages, or Go-bags. I hope you enjoy this Instructable! If you find it useful, please vote for it in the Outside Contest. Thanks for reading.
Step 1: Gather Materials
Here's a list of the parts I used:
1. Rotary tool with cutting blade (Dremel)
2. Soldering Iron
4. Wire Cutter/Stripper
5. Heat gun (if using heat shrink tubing)
6. Multimeter (for testing)
1. Solar panel (I decided on one because of its size. It fit right on top of the case without and extending edges. Realize that solar charging time is dependent on the panel size. I have a small panel wi)
2. Hand Crank Dynamo (I pulled my from a hand-crank flashlight. Just break open the case and pull out the dynamo. Be sure to keep track of the gear placement.
3. Project Case (I picked the case of a little screwdriver set I had that seemed big enough for all the parts and wasn't much bigger than my cell phone).
4. Charge Controller (TP4056, more on this later)
5. DC-DC converter (I chose one with 2 USB outputs. You can choose one USB output and split it, or just go with one output if you don't want to use a wireless charger)
6. Wire (16 gauge or higher. Any thicker and you'll be dealing with internal resistance and losing power)
7. Lithium Polymer Battery (As large as you'd like. I went with a 4200 mAH battery, which will charge my phone 3 times over without needing its own recharge) Be sure it uses PCB protection. Most phone batteries have this, but just be sure it's there if you're buying one from eBay like I did.
8. 2 Diodes (I used a 1N4001 Diode, but it's rated way higher than I needed it to be. So check the diode's spec sheet and just be sure it can accommodate the outputs from the solar panel and the hand crank).
10. Quick-Steel Epoxy, or other putty epoxy
12. *Optional* Wireless Qi charger if you decide you want to use wireless charging and your devices have that capability.
13. *Optional* USB cables. Depending on the placement of your DC-DC converter, you may want to use a small USB extension cable and a Micro USB cable to have a more convenient placement for your plug and wireless charger.
14. *Optional* Heat shrink tubing. You can also use electrical tape.
15. *Optional* Switch to disconnect the Wireless charger. If you don't use a switch, the induction coil will constantly put out power, draining your battery. This was a hindsight part for me, because I just disconnect the cable to the wireless charger when I'm not using it.
You can find pretty much every part you need for this build at www.browndoggadgets.com. They even have kits and guides for making solar charger. I got most of my parts from eBay, because I hadn't discovered them yet. To save money, I bought from mostly overseas sellers. Shipping from China takes at least 3 weeks, so I had plenty of time to wait. I also found some deals at a closing Radio Shack.
Scavenge parts where you can! You probably have a case lying around that you can use, and you may have a hand-crank flashlight that you can pull the dynamo from. You probably have a spare USB charger for your phone that you can pull the DC-DC converter from. You may have a small Qi charger lying around if your phone has wireless charging. You can even use a spare phone battery if you'd like.
When your parts arrive, be sure to check test them with a multimeter before you do anything. Check continuity on the circuit boards, check for at least a 5V output on the hand crank and solar panel, check for 3.7 volts on the battery (they usually ship with a partial charge).
Step 2: Create a Plan of Attack While You Wait for Parts to Arrive
I would highly recommend Youtube videos or maybe some Instructables to teach you about basic electronics before you attempt this project if you don't have a solid grasp of voltage and current behavior. You don't need to know much about integrated circuits or the engineering behind it all, just some simple electrical principles will help you understand what you're doing and what to look for in your tests of the device.
Step 3: Place All the Parts and Cut Some Holes
Drill 2 small holes for the solar panel wires to go through. Then secure the panel with Sugru. Sugru works so well for this part because it will create a solid protective ridge around the panel, as well as provide an anti-skid surface for wireless charging on the other side. Make a ridge that is higher than the panel, so that you can prevent scratching of the panel if it lays on that side. Allow the Sugru to cure for the specified time on the packaging (24 Hours, I believe). In the meantime, you can cut a hole in the bottom of your case to hold the dynamo. You want the dynamo inside the case, and the hand crank outside, so cut just enough of the case to allow the gears and motor inside. Secure the dynamo with epoxy putty. This stuff cures quickly so be sure you have everything in place and there is no putty in the gears. It helps to spin the crank while its curing just to ensure the movement isn't impeded.
Next, place (don't secure yet) the circuit boards and cables where you planned to. Ensure a good fit and make sure your case can close still. From there, measure the lengths of wire you'll need to make all the connections. You'll need 2 coming from the DC-DC converter, as well as any wires you may need to extend the battery, solar panel, or dynamo motor to the charge controller.
Once everything is in place, mark and cut your ports with a Dremel or maybe a utility knife if your case is plastic.. You'll need a port for the micro-USB port on the charge controller, one for the female USB plug, and an optional port for the switch if you're using a wireless charger.
Another note on wireless charging: Place the coil so that there is as little case material as possible between the coil and the outside of the case. A lot of these coils only work over a space of a few millimeters.
Step 4: Understanding Your Parts/Set Up the Diodes
DC-DC Converter: This device allows the Voltage from the battery to be stepped up from 3.7 V to 5 V to make it usable to the USB ports, which require 5 V. I chose one with 2 USB ports; one for a USB extension cable to reach the port I had cut, and another to connect to a micro USB cable to the wireless charger.
Solar Panel: Solar panels are photovoltaic cells that convert sunlight to electricity. However, they are inefficient, and put out only a couple hundred milliamps at best. Remember, Power=Voltage*Current. More power at a given voltage (must be 5V at least) means higher current, but also means increased size and cost of the panel. My panel is small and therefore weak, only putting out about 167 mA at 6 Volts. (6*0.167=1 W). At 167 mA, it would take 25 hours of direct sunlight for my battery to get a full charge, which is why I added the option of a hand crank dynamo.
Dynamo: A dynamo is a mechanical generator. Generators are motors working backwards, instead of using electricity to spin the shaft, the shaft is spun to create electricity. The faster you spin the shaft, the more power is produced. You can test this when you hook up the motor to the charge controller. Spin it slowly and nothing happens because you're producing less then 5 Volts. Spin it faster and you'll see the red charging light weakly show up. Spin even faster and it'll get much brighter. To allow for faster spinning, the gears create a high ratio so that one spin of the crank means many spins of the shaft. My crank only works in one direction (counterclockwise) but some dynamos will work both directions.
Wireless Charger: This is basically just an induction coil that transmits power over a short distance to a receiving coil. My tablet had such a coil built into it, but my phone (Galaxy S4) required an add-on coil that hooked onto the battery. Wireless charging is slow, but convenient. If you want to do wireless charging on this project, do not use a metal case. Metal will impede the induction between the coils.
Step 5: Solder Everything Together and Test
You have a positive and negative input terminal on the charge controller, and a positive and negative "battery" terminal. Your power comes from 2 sources (3 counting the micro-USB), so you'll have to splice together the positive and negative wires from the solar panel and the dynamo. Just tin and solder the wires together, then solder that connection to the appropriate terminal on the charge controller. Orient the wires to that their placement won't interfere with the charge controller's position or block the micro-USB plug's port on the case.
Now you'll want to solder wires onto the DC-DC converter. Make sure they're an appropriate length to reach the charge controller. Next, you'll do the same thing as before with the battery and charge controller wires. Solder the positive wires together, then solder that connection to the positive terminal on the output side of the charge controller. Do the same with the negative side.
Boom! That's it, all the connections have been made.
Now you'll want to test these connections and adjust them as necessary. Check that the hand crank works: spin it and look for the charging light. Put the panel in the sun and look for the light. Then plug a micro-USB cable into the plug on the charge controller and look for the light. Once your battery is charged, check that the DC-DC converter works by either plugging in a USB cable and charging your phone, or checking the plug with a multimeter for 5V.
Step 6: Secure the Parts
You're almost done!
Step 7: Finish Up and Take It Out for a Spin
Organize the cables, make sure nothing is pulling on the wires, and close up the case! Secure it however you'd like. My case has a latch that I use to easily open it up and unplug the wireless charger when it's not in use. But again, you can opt to add a switch to the converter to control this without opening the case.
Bonus note: You can unhook the hand crank and use it as a prop for solar charging to get it into direct sunlight. Just turn the crank to position the panel in the best angle to get the most sun.
Charge up the battery however you'd like: plug it into a wall, put it in the sun, or crank until you see a blue light.
You now have a large capacity power bank with multiple charging options and Qi capability! Great Job. Looking back at my constraints, I was able to meet every one of them. This is the ultimate tool to power your gadgets out in the wild. I hope you enjoyed this Instructable, and if you make it yourself or have any comments/critiques on this build please share them with me!