Wireless charging – charging your smartphone without a cable is this easy
You know the situation: yet again you didn't put the charging cable away properly because you didn’t want to lose out on a few more minutes sleep and needed to get things done faster. As a result, the cable was slightly damaged and now has a loose contact. But now there’s an alternative to trying to find the right position to charge the phone or buying a new charging cable: wireless charging. Despite the name, however, wireless charging is not entirely wireless.
How wireless charging works, what are its advantages and disadvantages and how to check whether your phone is compatible with it, is the subject of this blog post.
The topic at a glance
- How does wireless charging work?
- What are the advantages and disadvantages of wireless power transmission?
- Does wireless charging work when the phone is in its case?
- Which phones can be charged wirelessly?
- How can you tell whether your phone can be charged wirelessly?
- Can wireless charging damage the battery?
- Is wireless charging faster than using the normal charging cable?
- Can you retrofit wireless charging to your phone?
- Which devices can be charged wirelessly?
- Does a wireless charger consume more power than a normal charging cable?
- Wireless charging under the Qi standard
- What other transmission standards are there?
- How long does it take for my phone to go from 0% to 100% with wireless charging?
- Is wireless charging harmful to humans?
Wireless charging works by induction. This term probably still sounds vaguely familiar from physics lessons. Induction is a transfer of electrical voltage from one coil of wire to another. Induction is sometimes also referred to as inducing. The main principle is that the more turns the coiled wire has, the higher is the voltage transmitted. The induction charger has a coil, as also does the phone. But note: wireless charging is not possible with every mobile phone.
- charges not only smartphones but also tablets and smartwatches
- some chargers can charge multiple devices at the same time
- chargers are sometimes integrated in cars or tables -> no more searching for a power socket
- USB socket is freed up
- more expensive than a charging cable
- energy loss of approx. 15%
- charging does not (yet) work at a distance
Wireless charging works with the smartphone in its case provided this is not too thick or made of metal. Otherwise there is a risk that the phone cannot be charged. If a magnet for a phone holder is attached to the phone, this should be removed, as it may interfere with charging or damage the unit itself. The same applies to magnetic strips such as those found on a credit card, or RFID chips.
In 2008 the Wireless Power Consortium was founded with the aim of creating worldwide compatibility of wireless chargers and power sources. WPC now has 500 member companies consisting of large and small businesses. These include Samsung, Apple, LG and other smartphone manufacturers. Samsung has supported wireless charging since the launch of the Samsung Galaxy S6. Apple devices has been compatible since the iPhone 8 and iPhone X.
Wireless charging is possible on all devices that carry the Qi logo on the packaging. The logo consists of a black q and i. The letters form a singe unit with the dot of the i placed above the q.
The advantage of wireless charging is that the charging process stops as soon as the battery reaches 100 %. It resumes, however, as soon as the battery loses 1%. This can damage battery performance. During the charging process, the smartphone uses its own battery, which can put a load on the battery’s storage cells and damage it.
At present, wireless charging can take longer than via a charging cable. The reason for this is the amount of current, measured in milliamperes (mA). A current flow of 1200 mA to 2000 mA is normal in a charging cable, whereas only 500 mA to 800 mA can be achieved with wireless charging. In addition, 10 to 20% of the energy is lost during inductive charging, which can result in the charging time for wireless being doubled.
Older devices that do not have a Qi logo on the packaging can be retrofitted. This is possible by means of a special mobile phone cover in which a coil is integrated. The power induced in the coil is passed to the phone battery via a USB or Lightning cable.
Other technical devices can now also be charged inductively. Tablets, Bluetooth headphones and even laptops can be charged wirelessly. These can be charged via the charging station, and depending on the charger manufacturer, can sometimes be charged simultaneously. Certain household appliances can also be charged by induction. These include robot vacuum cleaners and electric toothbrushes. For a quick search, Wireless Power Consortium offers a product search: https://www.wirelesspowerconsortium.com/products
German consumer organisation Stiftung Warentest tested various inductive chargers and found that they are little power guzzlers. They consume some 50 % more power than a conventional charging cable. If you leave your phone on a wireless charging station, it consumes over 2 watts, in contrast to the plug-in charger, which only consumes 0.05 watts. This means you pay about €3 more per year.
The Wireless Power Consortium has set a defined standard known as Qi. This carries a defined standard for both safety and operation. WPC thus ensures that manufacturers of charging devices can only carry the Qi logo if they are safe, effective and compatible with the overall Qi ecosystem. For purchasers, the logo provides information about the rechargeability of the smartphone.
In addition to the Qi standard, there are two other transmission standards: Powermat and Rezence.
Like the Wireless Power Consortium, the Power Matters Alliance is a community of global industry leaders who want their Power 2.0 product to make the future wireless and environmentally friendly. This system is also based on induction. Powermat is familiar from its recharging offerings in Starbucks and McDonalds outlets.
Unlike its competitors, the Alliance for Wireless Power relies on resonant magnetic coupling. This method is also based on the induction principle. The advantage of this variant, however, is that the voltage loss is lower. In 2014, A4WP and the Power Matters Alliance joined forces.
The time varies with each charging station and with the smartphone itself. There are some devices with which a Samsung phone charged faster than an iPhone or vice versa. In general, however, you should be prepared for charging to take longer than with a charging cable. If you compare the chargers, you will find that it can take around three to four hours.
Experts’ opinions differ widely on this question. The magnetic field of the charging stations and their range are currently very low; indeed, with some chargers, the exact location of the coil must be found for charging to take place at all. Manufacturers also design inductive charging stations in such a way as to ensure that there is no risk for the consumer. Despite this, some experts believe that even the smallest amount of electromagnetic radiation can be dangerous. This is opposed by the experts who say that it is harmless. This issue will play a greater role in the future and will require closer examination when inductive chargers have a greater range.
If you remember just before you fall asleep that you’ve forgotten to plug in your mobile phone and want to avoid turning on the light, wireless charging is a good alternative. However, if you need faster charging, there is currently no way around a charging cable. Integrated charging stations in cars are also a convenient and easy way to charge your mobile phone without a cable interfering with your journey. This method is also much safer than using a charging cable. While charging cables can be manipulated to upload harmful software to your device, this cannot happen with wireless charging. A huge advantage of a wireless charging station is that any device, regardless of operating system, can be charged. Thus even an iPhone owner in a Samsung household can charge his mobile phone if caught out without a charging cable. In future, inductive charging will play a very important role in all of our lives and will make wireless charging possible everywhere.