Charging Under Different Lenses

Diego Celis
May 26, 2018

Submitted as coursework for PH240, Stanford University, Fall 2017


Fig. 1: One of the many chips engineered by Qualcomm to support fast charging capabilities (Source: Wikimedia Commons)

Since the dawn of the technology era, humans have struggled with storing and managing energy for their devices. While it is true that we have made monumental leaps in battery technology, battery technology still remains as one of the least developed areas in modern advancements. This, however, is not because there is no demand for it. It quite literally is the case because it is a very difficult field to progress. At best, battery technology improves linearly. While this may seem good at first glance, the reality is that it pales in comparison to the advancements made in related fields, such as storage and processing power, where technology is evolving at an exponential rate.

That being said, the battle against heat dissipation, power yield loss, and charge and discharge rates has not been in vain. Advancements in the field have allowed for the introduction of comparatively "fast" wired charging, as well as entirely wireless charging, also known as inductive charging.

Fast Charging

In a nutshell, fast charging is a technology that takes advantage of the voltage conversion abilities of power adapters and uses wattage to shorten charging time for devices with fast-charge enabled batteries. Formally, for a fast-charge enabled battery, the required input power PDC is

PDC (kW) = IDC × Vmax / 1000. (1)

where IDC and Vmax are the charging current and voltage of the battery pack in question. [1] To give a more substantive appreciation for fast charging, a charging current of IDC = 6 Amperes is 3.745 × 1019 protons per second.

In practice, this technology allows for charging speeds that tend to be two to three times faster than conventional charging. Technology manufacturing company Qualcomm has launched its own fast-charging technology, Quick Charge™, the latest iteration of which can charge up to 20% faster than the previous iteration, with both significantly faster than conventional charging. [2] It is important to note, however, that this technology arises from the very basic principle of creating circuitry that allows for a certain power to reach the battery at once. There are other factors to consider as well, such as battery expansion that may occur if batteries are charged too quickly. Fast-charging enabled devices would accommodate this expansion to a slight degree within their enclosures. This is distinct from having all the required circuitry and controllers that communicate with the battery and the charging adapter. One of these controllers used by Qualcomm is shown in Fig. 1.

Wireless Charging

There are several benefits to wireless charging. Firstly, there is no more hassle dealing with cables, which also allows for all wireless charging enabled devices to share a commonality in the ability to be charged by any one wireless charger. Secondly, it allows for devices to be more easily waterproofed, for the ports and openings that would usually exist for wired charging could be removed. This provides a design that is more robust against not only water, but also dust and other particles. Thirdly, and perhaps most importantly, they allow for devices that are normally hard or expensive to charge to be charged. A device like this could be a pacemaker. [3]

All these benefits, however, come at a price. Most notably, wireless-charging enabled devices must have at least one of their sides covered in glass, in order for inductive charging to work. Regardless of how durably the glass is constructed, it still poses a severe vulnerability for physical damage, especially in mobile phones. Coupled with this is the fact that wireless charging simply cannot be of high power by nature. This problem arises due to the fact that wireless charging, compared to wired charging, heats up the phone or device it charges significantly. As a result, with current technology, it is deemed unsafe to push high power through wireless charging, as it may pose a physical risk to consumers. This is not to say that power transfer is inherently inhibited due to the lack of wires. In fact, wired charging and wireless charging do not differ in the amount of power they can deliver. Instead, it is the collateral effects of employing large magnetic fields in households causing problems that make such power transfer rates unfeasible with wireless methods at the present time.


Both charging methods have benefits and drawbacks relative to one another. The good news is that, at the end of the day, companies give the consumer the option to opt into either or both options. The ultimate goal, however, still remains far away: true wireless charging. Overcoming the challenges related to charging without point of contact is a difficult task, but one that will surely change the way that businesses and consumers interact with their products at a large and transformative scale. Until then, these methods will satiate the pragmatic and the forward-looking consumers alike.

© Diego Celis. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] A. Burke, "Fast Charging (up to 6C) of Lithium-Ion Cells and Modules: Electrical and Thermal Response and Life Cycle Tests," in Lithium-Ion Batteries: Advances and Applications, ed. by G. Pistoia (Elsevier, 2014).

[2] A. Beall, "Charge Your Phone in Five Minutes: 'World's Fastest' Battery Promises to Go From Flat to Full 16 Times Faster Than Standard Chargers," Daily Mail, 19 Feb 16.

[3] X. Lu et al., "Wireless Charging Technologies: Fundamentals, Standards, and Network Applications," IEEE 7327131, IEEE Comm. Surv. Tut. 18, 1413 (2016).