Fast Charging Explained: The Necessary Evil

Remember the days when you had to leave your phone on charge for hours? Smartphones even with low battery capacities used to take over 3 hours to charge.

The times have changed now, and we have started seeing smartphones with humongous battery capacities and great charging speeds.

In this article, we will discuss the working of Fast Charging in depth. It is a technology found on a lot of mid-range and high-end smartphones. It helps charge your device quickly while you make yourself a cup of coffee.

There are a lot of different fast-charging standards developed by smartphone manufacturers that we are going to review. Towards the end of the article, we shift our focus to the drawbacks of Fast Charging and why fast charging is not present on every smartphone yet. 

    How does Fast Charging work?

There are two factors that govern the amount of power delivered to the battery. The first one being the amount of current flowing through it and the other one is the electric potential applied to it in order to make it flow. In simpler words, the potential is nothing but the voltage applied to the terminals.

Power is the product of Voltage and Current, and by bumping one of them or both of them, devices can be made to charge at a much higher rate. That is the fundamental principle behind fast charging.

The industry-standard USB 3.0 port supports voltage and current rating of 5 V and 1 A which makes it capable of delivering 5 W of Power. This is what slow charging looks like. 5W of power is nowhere near where fast charging reaches. 

In the last few months, we have seen companies like Oppo, Vivo, Realme, iQOO, Xiaomi all announcing smartphones with a 120 W charger. 

There are a lot of mid-range smartphones available in the market that support 65 W of charging speeds. But, if you think that these smartphones will charge up 10-20X faster than smartphones with regular charging, you are in for a disappointment.

The charging speed of a battery is inversely proportional to the amount of charge held by it. A completely discharged battery charges at a much higher rate compared to a charged battery. We are not going to get into the power electronics of battery charging, but let’s consider an analogy to understand why this happens.

If you soak a dry sponge in water, it will absorb the water easily. As it soaks up the water, it won’t be able to soak more water as quickly as before. The battery is like a sponge too. It absorbs charge quickly when it is empty and starts resisting the charge as it fills up. 

    Issues with Fast Charging

The technology is fairly new and has some serious issues with it. We need some major advancements in Battery Technology to reduce the extent of degradation. Here are the issues with Fast Charging:

It reduces the Battery Capacity

You might have noticed all the smartphones that support fast charging are quite big. The reason is, due to a design limitation, the size of the batteries that support fast charging is more.

This means that the size of a battery that supports fast charging is more than that of a regular battery. The battery capacity goes down due to size limitations.

It degrades the Battery Health

When you purchase a smartphone with fast charging, the manufacturer tells you how fast the device will charge, but what they don’t tell you is how long will the battery live.

While it is a well-known fact that charging slowly degrades the battery capacity, fast charging is known to cause a dip in it.

It Overheats the Phone

Electronic devices hate heat. Smartphones are no exception. The amount of heat generated during fast charging is significantly more than that generated during a regular charge cycle. The heat is produced due to the losses taking place in the charger and the smartphone.

The ambient temperature has a major impact on the battery of smartphones. As the temperature increases, the battery life keeps on reducing. The amount of charge holding capacity lost when charging the battery at 30°C is less when compared to charging it at a temperature of 40°C.

It gets slow with Charge and Time

If you notice closely, when you purchase a smartphone that supports fast charging, you will see that the company claims to offer to charge speed up to a certain value. They do not guarantee that the charging speed will be equal to the value that they have mentioned on the box at all times. 

The charging speed will be a lot less than what the company has claimed once the battery fills up half. The fact that the overall charging speed of the phone keeps on reducing with each passing charge cycle makes things worse. 

At the end of 2to 3 years, the battery life of your smartphone could be reduced to as low as nearly half of its initial value. But again, only a small population use their smartphones for more than 2 years. 

Here is a video by Mrwhosetheboss which explains the problems with fast chargers in detail:

    How to check your Battery’s Health?

If you have made it to this point in this article, it is natural for you to feel worried about the battery life of your smartphone. So, we are going to tell you how you can check the charge holding capacity of your Smartphone.

Android Users

All you have to do is to download an app called “Ampere” from the Google Play store. The application has a lot of interesting features that let you know the status of your battery. It will tell you everything from the time required to charge your battery completely to the amount of charge capacity left in it. 

Android Ampere App

The premium version of the application lets you customize widgets and set them up to get notifications when the battery level reaches around 90%. This lets you prevent overcharging it and extends its overall life.

iPhone Users

iPhone Users can check their Battery Health by going to Settings -> Battery -> Battery Health.

iPhone Battery Stats Screen

iPhone Maximum Battery Capacity

Optimised Battery Charging is an interesting feature that intelligently optimizes that the charging of your iPhone past 80%. You can learn more about it here.

On this screen, you can also check your iPhone’s Battery Health.

    Smart Charging

iPhones and some flagship android devices have introduced some really great features to protect your battery life from degrading rapidly.

If you have an iPhone running on iOS 13 or a newer version, the phone will learn your charging habits using Optimised Battery Charging as discussed in the previous section.

If you plug in your smartphone for charging every night, the phone will keep track of the time when you wake up. The phone will charge up to 80% and wait for a few hours. 

Before you wake up, the battery will continue charging from 80% and go on until you wake up. This prevents your phone from staying in the highly unstable 90-100% zone, thereby keeping the Battery Health intact.

Similar features are seen on Samsung Galaxy S series phones too.

    The Sweet Spot

Since the 100W+ charging is relatively new, the technology is quite unstable. As the charging speed goes up, many new problems start showing up. Manufacturers have split the batteries into two parts to allow them to charge at the maximum rate possible.

This not only increases the overall size of the device, but it also increases the cost of the battery. The sweet spot lies somewhere around 30 W. A smartphone with a 5000 mAh battery and 30 W charger will be able to meet most of the requirements.

Such smartphones are available already in the market. There are a lot of Android smartphones in the budget segment that have a 5000 mAh battery and a 30 W charger. The best part is that they don’t burn a hole in your pocket.

In the future, we may start seeing smartphones that can charge up completely within a matter of minutes. Imagine having a smartphone that charges completely while you have your morning breakfast. It is unclear when we might get such features in smartphones. 

It all depends on how fast the advancements in Battery Technologies are made.

The thing with the technology is that you never know when it might saturate. We still have the same FHD display that we had on smartphones 5 years ago. 4K displays still haven’t made their way to mainstream smartphones, and it’s 2020 already.

It is tough to predict if a particular technology might see a significant upgrade in the near future. However, one thing is certain: the advancements in electrical engineering will keep refining the charging experience for all of us. 

Soon, ‘fast charging’ will be a reality for not only smartphones but for all of the appliances spanning everything from laptops to electric vehicles.

If you want to know the list of best smartphone processors, you can check out our Smartphone SOC Rankings.

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