Is Fast Charging Really Good For Your Phone?

Skull and crossbones sign on a phone screen
Is Fast Charging Really Good For Your Phone?

Over the years, tech has evolved to solve every problem that it once faced. The same story goes with smartphones, they are able to do a lot more today than they once could.

There are some limitations though that are just too difficult or even impossible to overcome. These limitations almost always have to do with materials.

One such limitation exists with phone batteries. One thing that people absolutely hate about their phones is having to charge them every day or every two days with huge phone batteries nowadays.

Companies have addressed this problem in two ways, first, by increasing the battery size, which we see getting bigger and bigger every year. Second, by reducing the charging time, which we see getting less and less every year.

The first solution is quite good, but there is only so much battery that one can fit inside these little machines. Hence, the second solution exists, but there are doubts around this solution being very viable in the long run, Which is exactly what we are going to talk about in this article.

Battery Degradation

Battery degradation is one of the worst if not the worst aspect of phone aging, specially with phones having relatively tough to remove batteries for some time now. You know what it is like if you have noticed that you have to charge your phone more frequently after you have owned it for a year or two.

I have covered battery degradation in detail and have also added some tips to slow it down in this article. But I will briefly cover it here as well. Now, before understanding how these batteries degrade, we have to first understand a little bit of how they work.

The batteries that phones have are Lithium-based batteries. There are two types of these, one is Lithium-ion(Li-ion) and the other is Lithium-polymer(Li-po). Both of these have slightly different applications as they have different pros and cons. Li-ion is the one more widely used as its benefits overtake those of Li-po by a little.

Find out more about the differences between the two batteries, and their uses.

Lithium batteries have three components, a Lithium Cobalt oxide cathode, a graphite anode, and an electrolyte. Electrons move from the anode to the cathode and this flow of electrons is what generates current. These electrons leave positive ions in the anode, which then move to the cathode to become stable again. When you charge a battery these atoms are pushed back to the anode, this completes one charge cycle.

These cycles cause the materials of a battery to wear off over time. A battery still degrades though, even when you have not been using it, reactions still take place inside the battery and cause degradation. To put it simply, unfortunately, these batteries just do degrade. 

Dead battery illustration with expressions
Is Fast Charging Really Good For Your Phone?

The only solution to this problem could be to replace the materials used for the battery or to replace the technology.

There are a few external features like heat and voltage that speed up battery degradation. This is where fast charging and doubts related to its viability come into play.

Potential Effects Of Fast Charging On Battery Health

While selling fast chargers companies usually talk about Watts, which is basically power that the charger can output. A few years ago, 10W and 15W chargers were the ones called fast chargers, but these would look puny in front of today's chargers.

Today's common standard for fast chargers is around 30W to 60W. But as is the case with everything in the tech world, companies haven't stopped there. In 2020, we have seen chargers capable of supplying 100W and even 120W power.

These chargers can take your phone from 0% to 100% in around 20 minutes. Amazing, right?

But there is a cost that you might have to pay for it. One thing you need to understand here is that this high power is attained through high voltage and high current. Voltage times current gives us power, therefore, high current and voltage.

Both high voltage and high current are dangerous for the battery. High voltage in itself, puts a lot of stress on the battery, high current on the other hand causes the battery to heat up. So, the current might not be directly affecting the battery, but it gives rise to one of the biggest factors that badly affect battery health, which is heat.

A phone battery retains around 80% of its total capacity after around a year of typical use, increase the temperature of the battery by 10°C and this number can go down to around 60%.

The ideal range for a battery to stay in is from 30-40°C. A 50W charger works while staying under that 40°C mark, but a 120W charger can go higher. This is shown very well in this article by Robert Triggs from Android Authority, he also found out that a 120W charger only delivers around 80W power, which is nowhere near the advertised 120W.

In Their Defence

Now, you may be wondering that if fast charging is so dangerous for batteries then there must be something that companies have done about it. 

Let's talk about the heat first. Yes, there is something that they have done about the heat.

The phone charges in a smart adaptive way. If too much heat is detected then voltage and current are toned down and the charging speed is reduced.

Coming to voltage now, if heat is not detected then the battery is still charged at a high voltage, which is going to happen almost all the time. Again, as we already know, high voltage is going to speed up battery degradation.

One thing that could be said here in the defence of fast charging is that since the phone charges up so quickly, it doesn't spend much time under that high voltage. Therefore, the battery isn't affected by voltage a lot.

These things are true to some extent, but over time, a battery would still go through a lot of stress due to high voltage and heat, causing the degradation to speed up.


If I were to put it simply then yes, fast charging does add to battery degradation. But things are almost never that simple, are they?

There is no doubt that companies have done things to minimize this degradation as much as possible. While the part about chargers dealing with heat is true, the fact still remains though, that fast chargers make batteries go through a lot of stress over time.

As I have mentioned above, there are two solutions to the problem of having to charge your phone every now and then, and fast charging is only one of them. The other solution was to increase the battery capacity, this one also works to reduce the effect of degradation caused by fast charging.

Let me explain, the more battery capacity you have from the start, the more battery capacity you are going to end up with at every stage of degradation. A few years ago, a 3500mAh battery was considered to be big, after a year of use this capacity would fall to around 2500mAh and you would notice quite a big difference in your backup. 

Today, 4500mAh and even 5000mAh have become quite common. After around a year of use, a 4500mAh battery would retain around 3500mAh. So, you pretty much still get a battery capacity after degradation that you would've gotten in a new flagship phone from a few years ago.

The bottom line here is that, yes, fast charging does speed up battery degradation, but there are a lot of things that work against it and to reduce its effects. You probably shouldn't worry about it that much.

The Solution

There is still something that you should take away from this article. Upon seeing companies advertise insane stuff like 120W chargers, you might get really tempted. But if you actually try to know about it more, their claims are not even close a lot of the times.

In the very case of these 120W chargers, the power output doesn't even come close to 120W, it is only around 80W. Along with that, this charger would charge your phone in around 20 minutes, a 50W charger would do the same in just 5-10 more minutes. But a 50W charger would also produce less heat in the battery, which is actually better for the battery than having slightly less charging time. Around 50W is the sweet spot for fast chargers.

Besides that, the only permanent solution to battery degradation seems to be to change the materials used in batteries. Check out these articles if you are interested to know more about this.


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