The Science Behind Wireless Charging and Its Limitations

Place your device on a pad or dock and it charges without the trouble of cables. While the experience is almost magical, what goes on behind it is based on what we know of physics. Out of interest, the science behind wireless charging and the fact that it has some limits explains its not-yet-full replacement of wired charging.

How Wireless Charging Works

At the core of wireless charging is electromagnetic induction, which we first saw in the 19th century. When an electric current flows through a wire coil, it generates a magnetic field around it. If a second coil is placed nearby, the magnetic field will, in turn, induce a current in that second coil.

This is the base of what wireless charging is. This principle is used in charging pads or docks, which feature a coil linked to a power supply. As electricity goes through this coil, a magnetic field is produced. The device you are charging, for example, a smartphone, has a small coil within it. As the phone is placed on the pad, the magnetic field from the charger induces a current in the phone’s coil. That current is then turned into electricity, which in turn charges the battery.

This process is what we term inductive charging. What you find is that the coils have to be near each other and in the right alignment for it to work well, and this is the reason why many wireless chargers require you to position your device in a specific location.

The Role of Standards

In order for wireless charging to work between different devices and brands, there must be universal standards. At present, the most common is Qi (pronounced “chee”), which has set the bar globally for consumer electronics.

Qi sets the standards for what amount of power is transferred, the frequency of coil operation, and we see in place safety measures to prevent overheating or energy loss. Also, most smartphones that support wireless charging do in fact use the Qi standard, which in turn guarantees compatibility between chargers and devices no matter the brand.

Types of Wireless Charging Technologies

While we see inductive charging as the most common method, we should also note that it is not the only way to transfer power wirelessly. There are many approaches, which all present different pros and cons:

1. Wireless Charging Near Field

Requires close contact between coils.

Found in smartphones, earbuds, and wearables.

At short distances, very efficient, but for multiple device charging it is not the best.

2. Resonant Charging

Uses tuned resonance in the inductive coupling, which is at the same frequency.

It allows for a bit more space between the charger and the device.

It can charge multiple devices simultaneously, although the efficiency tends to be lower.

3. Radio Frequency (RF) Charging

Uses electromagnetic waves as a base instead.

Can charge devices over longer distances.

At very early stages of consumer use, we still see issues with efficiency and safety.

4. Magnetic Resonance in Large Structures

Applied in electric vehicle (EV) charging.

Larger coils and higher power transfer.

Engineered to handle slight misalignment between vehicle and charger.

Advantages of Wireless Charging

Wireless charging has become very popular for many reasons, which go beyond convenience.

• Reduced Wear and Tear: Since we aren’t plugging and unplugging, which causes wear and tear, the risk of damaging charging ports or fraying wires is reduced.
• Sealed Devices: Devices can have better water and dust resistance, which is achieved by not including exposed charging ports.
• Shared Charging Pads: A single charging station is compatible with many devices which use the same standard.
• Safer Connections: There is a lack of exposed electrical contacts, which in turn reduces the risk of short circuits or sparks.

Limitations of Wireless Charging

Although it is very appealing, wireless charging does have its issues, which in turn is why many people still go for the surety of wired charging.

1. Reduced Charging Speeds

Wireless charging is typically a slower process than wired charging. For instance, a modern smartphone may have a wired fast charge option up to 60W or more, which is not the case for most wireless, which range between 5W to 15W. While high-wattage wireless does exist, it also tends to generate a lot of heat and in many cases is tied to proprietary systems.

2. Energy Waste

Wireless charging is less efficient than using a wired connection. We see that some energy is lost as it is converted to heat during transfer. It has been reported that in some cases wireless charging may use up to 50% more energy than wired charging, which also is an issue when the coils are out of alignment. This issue becomes very large scale when we are talking about millions of devices.

3. Warming Process

Heat is a byproduct of wireless charging. Also, energy transfer is not perfect, which in turn causes the charging pad and the device to become warm. In the long term, excess heat may affect battery life, which is an issue for heavy users.

4. Posture Sensitivity

For optimal charging, the device must be correctly aligned on the pad. Out of alignment even a little bit will slow down the charging or even stop it. That is the reason many chargers include magnets or guides for proper placement.

5. Reduced Range

Inductive charging is at close range, which is usually a few millimeters. This reduces your mobility—you can’t really move around with your phone while it’s charging, which may require you to pick it up and break the flow.

6. Cost and Budgetary Infrastructure

Wireless chargers go up in price compared to their wired counterparts. Also, we see that to build out a wide-scale infrastructure—for instance, public charging stations—is more complex, requires special equipment, and integration into surfaces like tables or cars.

7. Device Interchangeability

Although we have seen improvements in standards like Qi, still not all devices support the feature. This in turn limits its universal adoption.

Wireless Charging in Everyday Life

Today, in the field of wireless charging, we see its greatest use in personal electronics. Smartphones and earbuds are at the front of that trend with their use of Qi, which in turn allows for easy at-home battery recharges. As for smartwatches, they have adopted this form of charging mostly due to the fact it does away with small charging ports.

In cars today, we see that wireless charging pads are put into dashboards and center consoles. But still, many drivers report that they are a slower and less reliable option than using a cable.

The largest scale of this technology is in electric vehicles (EVs). Some companies are reporting they have developed wireless charging solutions for EVs, which may see cars charge via a charging pad in the ground as the car parks over it. The base concept is the same but scaled up with larger coils and higher power transfer. Although very promising, we still see issues with cost, efficiency, and installation, which are in the way of wide-scale adoption.

Why Wired Charging Still Dominates

For a large part of the population, wired charging is the choice for which we have a few reasons. It is faster, better at what it does, and does not require that your device be placed in a precise position. In terms of fast charge technology, wired systems have seen great improvement, which in some cases allows smartphones to go from 0 to 50% charge in less than 15 minutes. Until we see wireless charging match in speed and efficiency, we won’t see the decline of the cable.

The Future of Wireless Charging

Researchers and engineers are working to improve wireless charging technologies. We see in the works a few innovations which may help to overcome present challenges:

• Higher Power Transfer: Efforts are being put into the development of wireless high wattage, which in turn will bring us charging speeds that are almost the same as what we see with wired charging.
• Better Coil Designs: Improved out-of-the-box performance in terms of device placement. Also, we see that multiple coil arrangements do better.
• Resonant and RF Charging: These new technologies will be able to charge over longer distances. Also, we may see devices in one room powered wirelessly, which are not in physical contact.
• Integration into Surfaces: Furniture, cars, and public areas will feature integrated wireless charging, which will increase its access and ease of use.
• Eco-Friendly Improvements: Reduce to a minimum energy waste and heat in large-scale wireless charging.

Striking a Balance

In the field of wireless charging, we see the application of physics to improve our everyday lives. At the same time, however, this comes at a cost. The convenience of simply placing your device onto a charging pad is balanced with slower charge times, generation of heat, and issues of energy efficiency.

Presently, wireless charging is a complementary solution as we speak, which in fact is not a full substitute for cables. We see it mostly for charging overnight and as a quick fix during the day, but at the same time people go for wired charging when it comes to performance and power efficiency.

Conclusion

Wireless charging is no longer a thing of the future; it is a mainstay of today’s tech. At its base is electromagnetic induction, which we learned of over a century ago but is only now being put to everyday use. It has the benefits of lasting longer, easy use, and cross-device compatibility, but also has issues like slow speed, inefficiency, and the requirement for devices to be very close.

The present state of affairs is that wired charging is still the primary method we see today, but what we will see in the future is very bright. As we put in more research time, we may one day have wireless charging which is equal to or better than what we get from a cable. Till then, it is a very interesting story of how science is improving what we put up with every day, at the same time also putting into perspective that each new thing we develop brings with it a new set of issues.