The mention of fast charging technologies for smartphones has become quite common lately. You’ve probably already heard of Qualcomm’s Quick Charge, OPPO’s VOOC flash charge, or OnePlus’ Dash Charge, which can juice up a smartphone’s battery to around 60 percent in just 30 minutes. So, how exactly do they work?

Most devices use lithium-ion batteries

To understand how these technologies work, knowing the basic principle of how a smartphone’s battery gets charged is a must. Most, if not all, smartphones today use a type of battery called lithium-ion (Li-ion). A Li-ion battery is composed of a positive and negative electrode and an electrolyte in between them. The lithium ions inside the battery move from one electrode to another, allowing the battery to be in a charging (storing energy) or discharging (expending energy) state.

The direction of lithium ions determines whether a battery is charging (positive to negative) or discharging (negative to positive).

Battery capacity is measured in milliampere hour (mAh)

Great, we’ve got some background on how Li-ion batteries work! The next question is how exactly do we determine the speed at which a Li-ion battery gets charged. You’re probably familiar with the rating used to gauge the capacity of a smartphone’s battery. If not, it’s the number that uses mAh (milliampere hour) as its unit of measurement. A larger number means larger capacity, which translates to longer battery life.

A 6000mAh battery will last twice as long as a 3000mAh battery. The same thing applies to charging: The larger the capacity of a Li-ion battery, the longer it takes to fully charge. The amount of current that the charger can output is usually the determining factor on how fast a battery can be charged, which is why a tablet charger that can output 2A (ampere) will charge twice as fast as a smartphone charger that can output 1A.

Another important nature of a Li-ion battery is that it doesn’t charge in a linear fashion. It’s easier to charge the battery when it’s nearly empty compared to charging when it’s nearly full. Think of it like packing a bag; it gets harder to put things in as it gets filled.

As mentioned, increasing the current used to charge a battery decreases charging time, but only up to a certain point. A Li-ion battery can only take in so much current, and increasing it past the threshold only results in dissipated energy in the form of heat. Therefore, if you use a tablet charger to charge a smartphone, it usually charges faster but also heats up faster.

Battery charging has evolved through the years

With all these things in mind, we can go back to the question of how fast charging technologies work. As its name implies, it allows rapid charging of a smartphone’s battery. This is usually done by increasing the power output of a charger, either by increasing the voltage or current that it provides to the device. You might ask if it’s safe to increase the amount of power we pump into our devices: Theoretically, it isn’t safe, but with the right hardware for monitoring and checking power output and temperature, things become safer.

Smartphones nowadays are smart when it comes to charging. Most devices today have a built-in chip for monitoring battery temperatures and the amount of power going through as the phone charges. This allows the smartphone to intelligently lessen or stop receiving power from the charger once the battery is full or if the battery gets too hot. That’s why when you leave your phone to charge, you’ll notice the charger and the battery heat up while charging, and once they’re done, both will stop heating up.

Taking things further are these new fast charging technologies that can provide more than half of a battery’s capacity in less than an hour. They work by pushing as much power as the device can handle to ensure the battery is charging at its maximum rate. As mentioned earlier, when a battery is at a low capacity, it’s easier to charge since the lithium ions have more freedom to move. This nature is what Qualcomm and other manufacturers take advantage of for faster charging.

Qualcomm’s Quick Charge gets better every year 

Qualcomm’s Quick Charge technology leverages on different power outputs — mostly voltage adjustments — for the charger, depending on the current battery capacity of the device. Thanks to the special chip installed on both the device and charger, the latter can actively adjust the power output depending on the device’s needs. So, at lower capacities, it delivers the highest power rating the device can safely handle, and as the battery gets more juice, the device communicates with the charger and tells it to provide less power.

Ever since Quick Charge was introduced, Qualcomm has continued its development and currently has five iterations: Quick Charge 1.0, 2.0, 3.0, 4.0, and just recently, 4+. Here’s a table to summarize what the first four iterations of Quick Charge are capable of:

Quick Charge Version Voltage Current Power (Watts)
1.0 5V 2A Up to 10W
2.0 5V, 9V, 12V 2A, 2A, 1.67A Up to 18W
3.0 From 3.2V to 20V, dynamic increments of 200mV 2.6A, 4.6A Up to 18W
4.0 Dynamic Dynamic Up to 28W

Quick Charge 4.0 builds on the success of QC 3.0 by adding new features: compliance to USB Type-C and USB Power Delivery; a newer version of Intelligent Negotiation for Optimum Voltage (INOV), allowing the device to determine the optimum power level to request from the charger; and the inclusion of Dual Charge which adds a secondary power management chip in the device for better thermal dissipation and more efficient charging.

Even though few smartphones supporting QC 4.0 have been released, Qualcomm has already launched an update, version 4.0+. It further improves the Dual Charge feature of its predecessor with the addition of Intelligent Thermal Balancing, which eliminates hot spots by moving current through the coolest path available during charging. Building on the already robust safety features of QC 4.0, this update goes one step further by also monitoring the temperature levels of the case and connector. The added layer of protection helps prevent overheating and short-circuit damage.

High-current charging for OPPO and OnePlus

Being sister companies, OPPO’s VOOC charging technology and OnePlus’s Dash Charge have the same method for charging faster, and they do so by providing high amounts of current (around 4A) while charging. The level gets lower as the device gets charged up. Again, thanks to the special chips installed in the device and charger, OPPO and OnePlus devices supporting these technologies can charge faster.

Quick Charge and VOOC/Dash Charge may both be fast charging technologies, but they have some differences. Quick Charge mainly leverages on the use of higher voltages, while VOOC and Dash Charge use high-current charging. OPPO and OnePlus also made sure that the charger takes in the bulk of the heat generated while charging, which is not the case for Qualcomm’s Quick Charge, wherein both the charger and the device heat up.

Because of the phone not heating up too much, OPPO and OnePlus devices can be used while fast charging without any issues. In addition, OPPO and OnePlus’ fast charging technology is proprietary, which means you’ll need the charger and cable that came with your device to use it.

Samsung has its own Adaptive Fast Charging technology

If you own a recent Samsung device, you’re probably familiar with Adaptive Fast Charging. This is essentially the same as Qualcomm’s Quick Charge technology, since Samsung acquired the license from Qualcomm to use its technology on devices that have non-Qualcomm processors. This means a Quick Charge adapter can be used on a Samsung device that features Adaptive Fast Charging and vice versa.

Fast Charging requires specific hardware

Keep in mind that to make use of such tech, you’ll need a smartphone that supports a fast charging technology and a certified charger and/or cable. If you’re using a higher-end phone that’s been released in the last couple of years, chances are your handset supports fast charging.

Summing thing up: Fast, quick, rapid charging, or whatever they call it, is technically just a smarter form of charging that takes advantage of how Li-ion batteries work. With all the prerequisites — a compatible smartphone and charger — you won’t be stuck near a wall outlet for a few hours just to receive an ample amount of energy in your device. Until better battery technology comes out, fast charging might be the only solution we have for a while.

Illustrations: Kimchi Lee

SEE ALSO: Why is USB Type-C so important?

SEE ALSO
Why is USB Type-C so important?

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