The release of the iPhone X heralded a new era of charging, popularising the Qi standard of using electromagnetic induction for wireless energy transfer. But what if I told you that Braun were using inductive charging technology as far back as the 1990s in their Oral-B electric toothbrushes? The technology has been available for many years, but has only recently gained momentum – why?

This Q&A with RPD electronic engineer Nathan Ruttley explores the benefits of wireless charging against its predecessor, the trusty cable.

M: What are the primary advantages of wireless charging?

N: Wireless charging has many advantages, the primary one being that the device can be completely sealed and hence waterproof, dustproof, and have no ports to gather dirt. From a design perspective, products can look more appealing too. To the user, products without ports can seem more sophisticated than their counterparts that require plugging in.

M: Do you think wireless charging improves the user experience of a product?

N: Yes – practically speaking, there are many situations in which wireless charging benefits the user during regular use, such as the device can have its battery “topped up” between uses. charging the product in a dark environment is easier to initiate (since there is no need to search for a cable), and similarly it is easier to retrieve the product when there is no need to unplug a cable. In general, there is less a lot less friction when charging a device wirelessly.

M: Are there any reasons an engineer would decide against wireless charging?

N: Well, the major downside of wireless charging is cost. There are many additional components required to integrate wireless charging in to a device, not to mention that the wireless charger itself is an additional cost on top of the standard charger. From a technical perspective, wireless charging generates more heat which can be damaging to a product and the charging speeds are lower.

M: With the rise in the use of USB-C, it doesn’t seem like wired charging is going away too soon. Are there any compelling arguments for wired charging?

N: Micro-USB is probably the most ubiquitous charger in the world and in a pinch you would almost certainly be able to find multiple Micro-USB chargers in any household. I’m sure USB-C will replace that in the next few years. Additionally, the charging speeds offered are generally higher, allowing devices to be put back into service quicker; and using wired chargers allows a device to be simultaneously used and charged.

M: It sounds like there are arguments for both wired and wireless charging. Is there a compromise between the two on the market?

N: Custom contacts and pads (think Fitbit, Juul, and cordless landline phones) fill the space between wireless and standard wired technologies. Custom charging docks facilitate fast charging speeds whilst offering a user experience close to that of wireless charging, allowing users to quickly place and retrieve the device from the charging station without having to plug in cables.

M: Are there any downsides to custom charging docks?

N: The compromises required for a custom contact and pad-based charger are that the outer casing may not be completely waterproof and uninterrupted as there will be two metal pads visible. Depending on the product, ensuring a waterproof seal between the casing and the metal contacts will require careful consideration during the design stage.