How Fast Charging Works: Everything You Need to Know

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how fast charging works
Whether it’s the fact that the 17% of people that owned a smartphone in 2008 grew to 78% of the population in ten years, or of entirely new markets suddenly emerging and quickly booming (think smart speakers and smartwatches, now at 13% and 20% respectively, as opposed to being negligibly small just ten years ago), we can very safely say that not only has the entire face of technology changed drastically in just under a decade, the progress that we’ve made in that decade itself is staggering.

A must-have accessory for our must-have smartphones (more crucial than the complementary things, such as earphones and best MicroSD cards), is a phone with fast charging capabilities and a dependable fast charging cable to go with it.

Yes, all chargers aren’t fast charging, and not all cables are compatible with their fast charging counterpart plugs, something which invites a discussion of watts and volts.

First, however, let’s start with the basics.

Why Do We Need Fast Charging?

If you’re always on-the-go (and there’s a high chance you might be, at most, if not all times), you’ll know how good a well-charged phone feels, and the panic that the battery ducking under 15% brings with it.

Even stocking up on power banks, and let’s say you have the best solar ones, only solves a portability problem, but not the problem of limited time.

Enter fast charging (also known as Quick Charge, Turbo Charge, Power Charge, SuperCharge, Rapid Charging, USB Power Delivery Charging, SuperVOOC, and such variations). All of these are either the same thing as or build upon Qualcomm’s licensed Quick Charge technology.

A basic USB cable is specified only to send 0.5 amps of current, using 5 volts – wherein A multiplied by V is equal to W – meaning that this results in a mere 2.5 watts.

Fast charging fills up the battery’s capacity for maximum charge quicker by increasing that current which is sent to the battery.

For example, compare the number quoted in the paragraph above to Samsung’s Adaptive Fast Charging’s 15W, or Motorola TurboPower 30’s reported 28.5 watts (utilizing USB Power Delivery).

Of course, fast charging is optimized and designed to work in such a way so as to not pose any damage to you or your phone.

However, just how much truth is there to that claim?

Is Fast Charging Safe?

The aforementioned Qualcomm, the pioneer of fast charging, states that modern large batteries do not have their requirements fulfilled by “traditional” battery chargers and charging technology. The full rated capacity – while still keeping within the range of safety standards and the performance intended by the manufacturer – is achieved by Quick Charge.

High currents of charge and their related issues – such as overheating, overcharging, over-discharge – are what contribute to the deterioration and decay of a battery’s life and quality. Modern batteries, equipped for fast charging, come with a controller which “controls” for overcharging and over-discharge. As soon as the voltage drops below 2.8-3 volts (the usual permissible value), it disconnects any load. It also stops supplying the current at it reaches its maximum value.

The controller, even without bringing fast charging into the equation, gradually works to lower the current to keep in within that permissible value (to 0.75C, then 0.5C, and finally going beyond 0.2C to whatever the minimum is, taking the last 10% or so, 0.1C, very, very slowly).

When talking about fast charging, let’s say iPhone’s fast charging, some manufacturers use multicellular assemblies connected in parallel, because of which both the batteries (total capacity 4000 mAh) receive half of the 4A current supply each. The 2A current in each battery is distributed among cells evenly, which means that the loss of resistance is as low as the current, meaning you get charging that is much more efficient – or, fast charging.

Simply put, lower and controlled voltages and high currents are utilized to boost speeds. Going forward, we’re thus very likely to see USB Power Delivery become a universal standard, one that will then be experimented with and innovated in by different companies.

To better understand USB Power Delivery, let us now have a rundown of the usual fast charging standards.

What Are The Different Types of Fast Charging?

Finally, here’s a rundown of what’s at the back-end of this technology. Knowing this can help you know what cables to use, what your device needs, and if you’re adopting best practices for fast charging your smartphone.

USB Power Delivery: USB Power Delivery, which first made its way onto the scene in 2012, implemented a data protocol – meaning they’re both on equal footing, in order to reach the maximum delivery of power – across all devices equipped with USB ports. iPhone fast charging utilizes this to work with up to 100W of power, although a happy medium is still 15W, also being used in tablets and laptops (especially Macs).

Qualcomm Quick Charge: While we’re waiting for USB PD to become the standard, let us not forget what the default global industry-wide standard once was. Qualcomm, who we’ve already talked about as being the pioneer in the field, was not only doing fast charges before USB Power Delivery, but their latest Quick Charge 4.0+ is compatible with USB PD as well, meaning faster speeds all around and the widest possible range of support.

Samsung Fast Charging: While many smartphones just use the Qualcomm technology using their own brand name, Samsung’s Adaptive Charging is one that does feature specific tweaks to the original proprietary technology. It’s the same with Motorola’s Turbo Charging, but they still ultimately build on Qualcomm Quick Charge, unlike…

OPPO VOOC: Oppo’s VOOC (Voltage Open Loop Multi-step Constant-Current Charging) is one that works quite differently from the USB Power Delivery or Qualcomm Quick Charge methods. Oppo Super VOOC and Huawei SuperCharge also work similarly: instead of increasing the voltage, these increase the amount of the current, with the aforementioned Super VOOC and SuperCharge, along with WarpCharge 30 (for OnePlus) being the fastest quick-charging smartphones out there.

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