If you have a smartphone that you use often, you'll know the struggle of having a dead or dying battery.
You have a few options available to you to solve this problem:
- Carry around an extra battery (if your phone has a removable battery)
- Carry around a power bank
- Carry around a spare charger.
- All of these options, while feasible, require you to carry something extra around, plug it in, and keep it handy while your phone recharges. Or you'll have to shut off your phone and replace a battery, then carry the dead one around.
What if you could wear something that would charge your phone just by putting it in your pocket?
- Imagine the convenience. No plugging in an awkward box or being stuck to a wall outlet, no disassembling your phone to change batteries and then carrying around a dead one. Just drop your phone in a pocket, in a bag, or set it on a desk or table, and stop worrying about a dead battery.
In this Instructable I will show you how to make a wireless phone charger that you can wear inside your clothes, or inside a bag or backpack, or even use as a standalone charger. This device will give your phone several more hours of use just by keeping it in your pocket when you're not using it.
Step 1: Video Tutorial
I will provide full written instructions in this Instructable, but you may also watch this video for some visual guidance if I fail to explain this project in words. If you like it, please consider subscribing to my YouTube channel,.JakeOfAllTrades.
Step 2: About Wireless Charging
Wireless Charging, AKA Qi Charging, is a relatively new technology in the realm of smartphones. A wireless charger uses induction coils to transmit and receive electrical current from charger to device. All you have to do is get the two coils close together your device will charge. Now, not all phones/tablets have this ability built in. Most new Android phones support Qi charging, but iPhones and older Androids do not. However, you can buy a receiver coil that will attach to terminals under the back cover of your phone, like this one, or this one. that plugs into the charging port of your phone.
Most coils work over a distance of about 2-5 mm, depending on how well it can induce a current into the receiving coil. The coil I've picked out will transmit 5 Volts at 1 Amp, meaning it's rated at 5 Watts (5V+1A=5W). It utilizes a micro-USB 5V input, so any standard micro-USB charging cable and adapter will work on it. However, it is a good idea to use an adapter that has at least a 1 Amp output, to support the specs of the wireless charger and ensure good induction.
I use a couple wireless chargers for my devices. I've affixed them to a little dock I've made on my nightstand. People have also incorporated wireless chargers into convenient places like furniture and car dashboards. But I've never seen anyone make one wearable though. But I figure most people keep their phones in pants or purse pocket when they're out and about, and a pocket's tight enclosure is a perfect environment for wireless charging.
Step 3: Materials
Here's a list of materials I used to complete this project:
- Wireless charging enabled device that you wish to keep from dying on you in the middle of the day.
- Pants or article of clothing or accessory with which you want to wear and charge your phone.
- Lithium battery charge controller with micro-USB input (TP4056 works pretty well in my opinion)
- 3.7V Lithium-Polymer battery (try to optimize battery capacity to size. I went with a 1200 mAH battery which will provide my phone with about 6 hours of power)
- Push-button switch. I took one out of a cheap flashlight.
- 3V-5V DC-DC converter with USB output
- Qi Wireless charger with at least a 1 Amp output (this should come with a micro-USB charging cable as well)
- Carrying pouch (I had this lying around from a little multitool I got for free, but any small carrying case will work)
- Epoxy Putty
- Small Velcro patch
I created a full list of materials on Amazon.com Here. Pay no attention to the prices, as there's a good chance you can find these components a lot cheaper elsewhere.
- Soldering iron with solder
- Wire cutter/stripper
- Small-gauge wire
- *Optional* Heat shrink tubing or electrical tape to protect your connections
- Sewing needle and thread
Step 4: Diagrams and Plans
I started out this project by drawing some diagrams and making plans for how I would accomplish this build. Here's a small write up of the connections and function that I've planned out:
- The charge controller will charge the battery via a micro-USB port from a wall charger. I wanted an easy, universal way to charge the battery, and make the system adaptable and safe. If I want, I can just plug the system into a wall and set up my phone or tablet on it just like a regular wireless charger, then when I 'm ready to go, pull it off the charger, put the system in my pocket and keep charging with a now full battery.
- The battery will feed the DC-DC converter, and the converter connects to the wireless charging board. The charging pad comes off that board and will be velcroed to my pocket in a position that allows charging whenever I put my phone in there.
- I want the battery and circuits to fit inside a small pouch. The components are all small enough to fit in this pouch, allowing for a light, compact and easy to carry system. My goal is to have the pouch clip onto a belt or outside pocket, with the charging pad connecting to the pouch from my pocket.
There will only be a 3.7 V LiPoly battery feeding the Qi circuit when it's not plugged into a wall. The battery will be charged via the charge controller, which basically regulates the current from the micro-USB and ensures a constant flow of about 4 V into the battery, suitable for charging. While the battery is rated to 3.7 V, the wireless charger requires 5 V to operate. Therefore, between the battery and the charger there will need to be a DC-DC conversion circuit. This circuit will step up the voltage from 3.7 V - 5 V to make it usable. The converter utilizes a USB output connection. This is convenient, because the Qi charging circuit uses a micro-USB input connection. This means that we can just use a standard USB to micro-USB cable for this connection. Once these connections are made, the components will be fixed together with epoxy and will be housed in the pouch with the Qi charging pad outside this pouch.
Now before you start soldering or splicing anything, get a rough idea of how everything will fit together, maybe draw your connections on a white board. Just be sure you know what you're doing before you start.
Step 5: Solder and Splice
Okay, now we can get to work.
- Start by soldering a couple wires on the input side of the DC-DC circuit. Make sure these wires are short to save space and make the build look tidier.
- Solder a switch onto the positive wire coming into the DC-DC circuit. This switch will shut off the power (due to the nature of induction charging, you will drain the battery even if there is no phone charging off the pad, this switch will shut off the power when it's not in use). Solder a short wire to the other end of the switch.
- Splice the wires from the switch and the negative side of the DC-DC circuit to the respective battery wires.
- Take these spliced wires and solder them to their respective terminals on the output side of the charge controller.
- Determine how short to make your micro-USB cable that will connect the DC-DC circuit to the wireless charging circuit. Cut this cable to length and re-splice the wires together...be careful to not cross any wires. *Optional* Use heat shrink tubing to cover and protect your shortened cable.
- Connect the DC-DC circuit to the charging circuit with this newly shortened cable.
- *Optional* You may choose to lengthen the wires that connect the charging coil to the wireless charging circuit, depending on where you will be placing the charging pad and how far it will be from the other components. Just de-solder the pad's wires from the board and splice some similar-gauged wire to the connecting wires, then re-solder them to the board.
That's all the connections you have to make! That wasn't so bad was it?
Step 6: Test It Out
Test everything with a multimeter. Basically you want to go down the line starting with the charge controller, testing every input and output of the individual components
- Try plugging in your charge controller with a USB cable and wall adapter. You should see 5V on the input side of the charge controller, and roughly 4V on the output side. This will tell you that the charge controller works properly
- Let your battery charge up for a bit. After about 5 minutes, unplug the charger.
- Now test the output side of the charge controller, you should see 3.7V. This will tell you that the battery successfully charged.
- Now check the input side of the DC-DC Circuit. You should see 3.7V as well.Next, check the output side of the DC-DC Circuit on the USB port. You should see 5V. This will tell you that the circuit is working properly by stepping up the voltage.
- Now check the input of the wireless charging circuit. You should see 5V again. This will tell you that the cable you spliced still works properly.
- Finally, place your Qi-enabled device on the charging pad. If it starts charging, then your charging pad and circuit are working properly.
- If any of these steps failed, try re-soldering or re-splicing the connections you made. Also check the internal components on the boards to see if there are any continuity issues. If so, you may need a new component.
Step 7: Make Things Stick and Pack It Up
Now that all of your connections are made and you've ensured the system works and is safe, you can package your components together and make a compact device for carrying around everyday.
- Assemble the components how you planned earlier. I chose to stick everything to the battery with epoxy putty. The battery is the biggest component by far, and easily fits the other pieces on it. The epoxy putty works as a heat sync and gives rigidity and robustness to the whole system.
- Just knead together the 2-part putty and use a small amount on the undersides of each component to stick it to the battery. The putty will harden in about 5 minutes and will completely cure in about an hour.
- Once your assembled system is together, you can stuff it into the pouch, or whatever carrying apparatus you've picked. Make sure your charging coil wires aren't rubbing on anything that will compromise them. You may actually want to protect them with some electrical tape if you're worried about it. Make sure your coil is long enough to reach where you want to wear it. If you're going to carry the pouch on a belt, make sure the coil can reach into your pocket.
Step 8: Make It Wearable
Find the right position for the pad in your pocket to accommodate charging.
- You want the pad to line up with the receiving pad in your phone when you put it in your pocket. Once you have that position figured out, sew some Velcro into your pocket at that position. Stick the other side of the Velcro to the charging pad. Test it out: Stick the pad to the Velcro in your pocket. Then put your phone in your pocket, and check to see if it's charging. You can also sew some elastic into your pocket to better hold your phone in place if it moves around while you walk.
- The nice thing about sewing Velcro into your pocket is that you can remove the charging pad to wash your clothes, and you can sew Velcro into multiple different pairs of pants to use this wearable no matter what outfit you choose.
Figure out a place for this device that works best for you.
- That's the beauty of this system, it can be completely customized to however you want to use it. Add a clip, clasp, carabiner, or any kind of fastener to place it wherever is convenient and comfortable on your person. Sew the pad's connecting wires to your pants to secure them or route them inside your pants to your pocket through a small hole for a more discreet look This system can be use in backpacks, briefcases, purses, cargo pants, or even an arm band...just use your imagination.
I hope you enjoyed this Instructable! You now know how to extend the life of your device's battery with a convenient and wearable solution. Thanks for reading!