Is Fast Charging Bad For Smartphones?- Truth Revealed..!

The fast-charging technology world is touching higher and higher levels every day. Earlier, a smartphone used to charge at 5W, but now we have touched 120W milestones.

Yes, I’m talking about Xiaomi HyperCharge and Vivo SuperVOOC 120W power bricks that fully charge a 5000mAh battery in less than 20 minutes.

But an obvious question everyone asks- is fast charging bad for smartphone battery health?

Fast charging is safe if you’re using the original charger and cable. Smartphone brands like Xiaomi, Oppo, Realme, etc., use battery protection circuits that control the charging speed smartly in the adapter.

The adapter supplies maximum current when your battery is totally drained and reduces the current output once it reaches 80%. Hence, it prevents your smartphone from overheating.

If you’re also worried about your smartphone battery health because you’re using a fast charger, this guide will be helpful for you.

What is Fast Charging?

Fast Charging

Let’s understand what fast charging is because it’s a common term that every smartphone brand uses as a marketing gimmick.

A typical normal charger comes at 5W, which delivers 1 Amp DC at 5 volts. This 5W adapter takes 3 to 3.5 hours to charge a smartphone battery from 0 to 100.

5W adapter is the market standard, and anything more than 10W can be presented as fast charging. But nowadays, all flagships come with 15W power brick out of the box.

There is no market standardization on fast charging, but higher wattage charges your device quickly.

Apple’s 20W adapter takes approx 1 hour to charge an iPhone 13 Pro battery. So, it’s definitely a fast charger in comparison to older 5W adapter.

But, Xiaomi 120W HyperCharge only takes 17 minutes to charge the Xiaomi 11T smartphone. It’s also a fast charger, but we can’t say 20W is the slow charger.

Does Fast Charging Ruin Your Battery Health?

Fast Charging 120W
Image Credit: GSMArean

Fast charging doesn’t ruin your battery health quickly because phone manufacturers divide the charging speed into two segments.

When your smartphone battery is completely drained, the chargers push maximum power to juice up the battery fast.

Once your battery recharges to 80% or 90%, the charging speed is decreased to prevent overheating.

You must have noticed this with your smartphone. Your phone charges quickly from 0 to 80, which takes more time to reach 100.

Also Read: Does Use Non-Apple Charger Ruin Battery Health

How Do Phone Companies Mitigate The Impact Of Fast Charging?

Higher wattage increases the chance of overheating, ultimately impacting the battery’s health because lithium-ions loses its power-holding capacity at a higher temperature.

So, how do smartphone companies mitigate the impact of fast charging on battery health?

Here are two techniques used by phone manufacturers to reduce the impact of fast charging-

1. Dual Phase Charging

Have you seen this claim by smartphone manufacturers – ‘this phone will charge 0 to 50 in just 5 minutes or 0 to 80 in just 10 minutes“.

They are using dual-phase charging techniques to mitigate the impact of fast charging on battery health.

The phone or power brick has a dedicated power management circuit that smartly manages the charging speed.

When your phone battery is completely drained, your power brick delivers the highest current to juice up the battery immediately.

In this phase, lithium ions quickly gain power without overheating. Once the phone recharges 50% or 80%, the power brick reduces the current to mitigate the scope of overheating.

2. Dual Battery Design

In this method, a 5000mAh battery is divided into two 2500mAh batteries. Now, the power adapter delivers the same power to both batteries, which reduces the charging time by half.

But, this method makes the phone bulky because the size of dual 2500mAh batteries is more than a 5000mAh battery.

Also Read: Can You Charge AirPods With a 20W Charger

How To Slow Down Battery Aging?

Typically a smartphone battery is designed for 800 charge cycles. This means charging your smartphone once a day will last 2.5 years without any problem.

But your charging style, uses patterns, and other factors also affect the battery’s health.

If you’re concerned about your battery health, follow these tips to slow your battery aging.

1- Avoid High Temperatures

Lithium-ion cells use an electrolyte gel that is permeable to Li-ion flow but impermeable to electron flow. If the temperature around the Li-ion battery is too low or too high, the electrolyte forms an SEI layer around the lithium. [study]

This layer reduces the charge-holding capacity of Li-ion batteries. So, if you want slow battery aging, avoid using your smartphone near too high or too low a temperature.

2- Don’t Drain the Battery To Zero

If you don’t want your phone battery to lose its power-holding capacity, never drain the battery to zero.

Lithium-ion batteries never like to be fully discharged. So, connect your charger once the battery drops below 20%.

3- Avoid Full Charging

Never fully charge your smartphone battery if you want a longer lifespan. Lithium-ion batteries go under higher strain when they’re fully charged.

Apple also recommends ideal charging range is between 20 to 80 percent. To extend the battery lifespan, Apple introduced Optimised Battery Charging in iOS and macOS, stopping your device from charging beyond 80.

4- Remove The Case While Charging

Most smartphone users put an armored case on the phone to protect against accidental damage.

But, these cases are not a good conductor of heat, and when you fast charge your phone, your protective case will trap the heat, which is not good for Li-ion batteries.

So, it’s better to remove your smartphone case while charging. If you’re not using super-fast chargers, there is no need to remove the case.

5- Use Certified Charger and Cable

Some smartphone companies put battery protection integrated circuits in their charging brick to control the charging speed.

If you’re using a non-certified third-party charger, it won’t control the current rating as per your phone requirements.

As a result, your battery will age fast and lose its capacity. So, it’s recommended to use the original charger and cable.


Fast charging will not affect your smartphone battery health as long as you’re using the original charger and cable.

Generally, the charging speed is reduced when your battery recharges by 80%. That’s why you have noticed that your phone charges fast to a certain limit, and then the speed drops.

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