Introduction: Add Wireless Charging to Any Phone: Using the LG-V20 As Example

About: Retired aerospace engineer with degree in Physics. Enjoy all things technical and like to hike in the Rockies.

If you are like me and plan on keeping your phone for more than 2 years, then your phone must have

  1. A replaceable battery, because the battery only lasts about 2 years, and
  2. And wireless charging so you don't wear out the charging port.

Now the easy solution is to add a charging reciever to the back of the phone that just plugs into the USB port. However, that option gets in the way of using the USB port. There may be times when a wireless charging pad is not available or you want to connect the phone to your computer. So I prefer to wire the receiver into the inside of the phone to keep the USB port open.

I added wireless charging to my previous phone, a Galaxy S3, but it is now 5 years old and needs replacing. So I went looking for a new phone. One with good features but still sporting a replaceable battery. My choice was the LG V20. What follows will be a discussion of how I added wireless charging to the V20, but also with general notes for those that may which to try it on their own phone. The concepts are the same, but implementation may vary.

do not do this if you are uncomfortable with any step.


Step 1: Gather the Materials You Will Need

You will need a clean, safe place to work that has good light and no one to disturb your work. You will be handling tiny screws, chemicals and a hot soldering iron. Make sure you have a safe place to stow the soldering iron so you or others will not get burned.

Items needed:

  1. Tools needed to disassemble your phone. I.e.:Jewelers screwdriver set, etc.
  2. USB cable that fits your phone. One you don't mind destroying.
  3. Knife or blade to strip and cut wires
  4. Possibly a small cutting/grinding tool for shaping plastic and making holes, etc.
    Mine would have looked better if I had used one.
  5. Soldering tools:
    • Soldering Iron with VERY FINE TIP.
    • Water soluble rosin to help tin the Iron and the wire.
    • Rosin core solder, NOT acid core!
    • A wet sponge to clean the tip with.
  6. 90% Isopropel alcohol if you can find it. 70% is probably OK, but use it conservatively.
  7. Magnification: Head mounted, free standing or an eye-loop. Phones have very tiny parts.
  8. Flashlight
  9. Lots of guts to do this on a new phone. I was risking quite a bit of money.

Seems like a lot, but each item has a part to play.

Step 2: Get a Charging Transmitter and Receiver

Charging Types

  • Qi ("chi") charging is currently the charging standard. There is the regular (5 watts & 1 amp) and now there is a "Fast" option (15 watts & 3 amps). For Fast charging you need both a Fast receiver and transmitter. I opted for the standard since I find that it is adequate for overnight charging and the battery on most phones will last the day under normal use.

Operation and Considerations:

  • Wireless charging is nothing but a split transformer, where one half transmits power via a high frequency magnetic field to the receiver side that then rectifies and smooths it to 5 volts DC.
  • Many phenomenon (like light) fall off in strength via a squared distance function (Strength / DxD). However, magnetic field strength is a cubed function (Strength / DxDxD). What this means is that the power transfer capability drops off very fast. Therefore, separation between the Transmitter and Receiver must be kept to a minimum, less than about 4 mm. Therefore, large fat and thick cases can make charging next to impossible unless you consider how to get the receiver closer to the transmitter. Receivers built into a phone prevent the use of thick protective cases. Also metal cases prevent the use of a receiver inside the case due to excessive currents in the case that use up the power and overheat the circuits. In my Galaxy S3, I used a thick case but got around it by taping the receiver to the outside of the phone back and removed the inner layer of the two piece case so that the separation was less than 4 mm.
  • Note that charging receivers have a special magnetic shield on the back side. This shield helps to keep the material behind the coils from interfering with the magnetic field and thus improving performance. if you decide to expose the receiver coil, do not remove this shield. You also want to make sure the receiver is mounted face out. The outside face will be marked in some way, perhaps as illustrated.
  • On the charging receiver if the positive and negative terminals are not obvious or marked then you may have to place it on a charging pad and use your voltmeter to identify the positive and negative points to wire to.
  • You can use most any transmitter since the new QI standard is backward compatible. That is it will detect if your receiver is capable of fast charging and if not will not overload it.

I chose a charging receiver that seemed reputable and I had seen evidence that when opened it had pretty copper wires. I wanted to see the insides, but additionally, removing the cover also gets the receiver coil closer to the transmitter coil. I intended to add a clear insulating case to protect it.

Step 3: Disassemble the Phone

You need to get into the phone to identify a place to connect your charging receiver. I will not go into detail here, since nearly all phones have disassembly instructions somewhere on the web. Suffice it to say I reviewed several of these videos for the V20 before I chose to buy the phone. The V20 is very easy to take apart. You may not need to remove the motherboard as I did and as it turned out I didn't need to. Be thinking ahead about how to route the wires out of the phone. At this point you may decide that this is not something you want to do based on the difficulty of disassembly or soldering.

Step 4: Be Familiar With the USB Pinout

You should learn what you can about the USB socket's pin-out. This is readily available on line for any type of USB socket. Shown is the USB Type C used on my LG V20.

In my research I guessed that the 24 pins of the USB Type C socket were arranged as shown in the upper left of the second figure. Using the pin-out diagram on the right I deduced the topside pin assignments as shown in the lower part of the second figure. However, there was no obvious +Vbus location to solder to. The pins on the socket are way to small to solder to, therefore, we must find another place to solder that we will verify with a volt-ohm meter. You have to make your own decisions about where to solder the wires and your capabilities.

Step 5: Verification: Make a Test Cable

You will need a cable to plug into the phones charging socket. You will use this to find the +Vbus inside the phone as well as verify the ground. Ground should be the socket casing itself. DO NOT PLUG A LIVE POWER CORD INTO THE CHARGING PORT. Placing power on the mother board when disassembled and probing around could destroy the phone.

Find a cable that fits your phones charging port. For me this was a micro usb with a Type-C adapter.

Strip the wires and identify the wires that are for the ground and the +5vdc (+Vbus). For a Micro-USB this should be Black for ground and Red for +5vdc.

Step 6: Find a Place to Solder the +5 Vdc and Ground.

Ground site: Set your ohm meter to "Resistance", "Ohms" or "Continuity". Plug your test cable into the phone. Attach one lead of your ohm-meter to the black wire of your test cable. Now touch the other lead to the socket casing and other places you may have identified as ground. You should get a zero ohms reading or a continuity signal. Now decide where you want to solder your ground wire. As part of deciding, look at any other phone parts that might obstruct that location. Also consider how you are going to route the wire out of the phone. Keep in mind also that you need a "large" spot to solder to. (As you will see later, soldering is difficult in these tiny spaces)

+Vbus site: Now connect your ohm meter to the red wire of your test cable. Now look for a "Large" spot with continuity to the red wire. You may find more than one. As you probe around, consider how you will route your wire each site you find.

V20 Results: In the figure you can see a plus and minus sign. These are the negative and positive sites I chose. As we continue you will see how fantastically great a location these turned out to be for routing the wire in my LG V20.

Step 7: Solder Your Wires On

Now, very carfully solder the two wires, red to Positive Vbus and Black to Negative. After soldering the wires, double check your continuity to the Black and Red wires of your test cable. Make sure they are not shorted to nearby components. Clean the resin off with the Isopropel alcohol and allow time for it to dry.

CAUTION: I had an almost needle point soldering iron with temperature control and had a hard time. As you can see in the first figure that it looked like I had bridged to the capacitor on the left. In the second I had used a razor blade to slice off a bit of the solder. Then in last figure I had cleaned it with 90% Isopropel alcohol and it doesn't look to bad. Notice the melted insulation. Notice how "big" this tiny wire looks.

NOTE: You should use the smallest insulated wire you can find. I used the wire out of the USB cable that I had used for my test cable. However, I found out, and you can see in the figures that the insulation melted. Wire with a high temp insulation would be better. Some heat shrink might work, but would likely make the wire too large.

NOTE: Isopropel alcohol is non-conductive. Therefore, it will not harm the electronics and it will also dry quickly. Excellent tool to have handy if you drop your phone into water. Rice can dry a phone but it can not clean it. Water often has dissolved salts that will leave conductive films on components when dry. A bath in Isopropel alcohol can clean and help dry the phone and has a better chance of restoring full operation.

Step 8: Routing the Wires

You should have already considered how to route your wires. Once I found the location of the wire attach points, I was able to make a better assessment of routing possibilities. Now that the wires were in place I could get even more specific. My V20 has a plastic cover over the mother board that I knew I would have to "sculpted" but it turned out to be easier than expected. I was able to run the wires alongside the USB port and then up at a right angle through the plastic cover. I know I did not want to drill holes in the back of the phone case, though I was prepared to if required. As it turned out the passage through the plastic cover just missed the metal back. Also the solder on the ground wire interfered with the cover, so I had to trim some material off of the inside of the cover at that location. The end piece of the V20 is plastic (contains the antennae?) and all I had to do was add a couple of small notches for the wires. I also added some clear packing tape to the metal back for insulation.

NOTE: I was planning on laying the wires on top of the inner plastic and having some very thin copper bend over the metal back into the inside to contact with the wires. However, I decided it would be easier to just attach the wires outside the phone. But I had removed the insulation from the ends of the wires before changing my mind. It would have been better to have left it on, decreasing any chance of shorting to the back cover. Some day I may move it inside anyway, but that will require additional sculpting of the internal plastic shield.

Step 9: Finish

Make sure you don't cross positive to negative and complete your installation. My V20 came with a clear plastic protective cover on the back so I did not need to add additional protection except for the bottom edge where the wires might short. So I put two layers of clear packing tape over the edge.

Placement of the receiver coil is up to you. Most phones center the coil however, depending on your transmitter size and shape you may have other ideas. Centering the coils on each other is almost as important as minimizing separation

You can refer back to the first figure for the final appearance. The receiver causes the back to bulge a little, but less since I removed the little round piece of metal in the center of the coil. I had put that there to assist with centering on my transmitter, which contains a magnet. However, it was not very effective and caused excessive bulge and separation, so I took it out.

Step 10: Results

Wireless charging is much slower that wired charging. I read that some expectations could range from 4 hours on up. A quick test on my V20 despite the note that it is "Charging Slowly" is that it might take up 6 hours to charge. This is quite acceptable since I will charge at night and so far battery life has been excellent.

The V20 could probably use a "Fast" charger since it is designed for fast WIRED charging. I just did not choose that. Partly because I already have regular "slow" chargers and the "Fast" ones cost more.

I hope this helps others, especially those LG V20 owners that miss the wireless charging.

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