here is what our mini study shows

During a recent screen share with my iPhone 15 Pro, I observed a maximum battery capacity of 92% after 258 charge cycles. This simple tweet generated a massive reaction, reaching 340,000 views in two days. Intrigued by the scale of the exchanges, I decided to explore how charging cycles affect the health of iPhone 15 batteries.

Apple iPhone 15 and 15 Plus // Source: Chloé Pertuis – Frandroid

During a recent screenshare of my iPhone 15 Pro, I noticed that my battery had a maximum capacity of 92% after 258 charge cycles. This tweet sparked a massive conversation, it reached 340,000 views in two days. This prompted me to further explore how charging cycles affect iPhone 15 battery health.

Source: Frandroid

What is a charge cycle?

A charge cycle is when 100% of the battery’s capacity is used, but not necessarily all at once. For example, using 50% of the battery today and recharging it, then using 50% again the next day, is one charge cycle. This measurement helps understand how many times a battery has been used and fully recharged.

On iOS, this data is accessible via Settings > Battery, but the number of cycles only appears on this generation of iPhone. This allows users to better track their battery health over time.

Logic: the higher the number of cycles, the more the maximum capacity of the battery tends to decrease

Following my tweet, I collected the data shared by other users in the form of screenshots. By analyzing this information, I generated a graph showing the relationship between the maximum battery capacity (in %) and the number of charge cycles. A general trend appears: the higher the number of cycles, the more the maximum capacity of the battery tends to decrease.

The correlation coefficient between the two variables is -0.636, indicating a moderate to strong negative correlation. This means that, generally speaking, battery capacity decreases as charge cycles increase.

Source: Frandroid

On closer inspection, we notice that the battery capacity drops sharply once below 100%. So I filtered the data to only keep those with a maximum capacity less than 100%. This analysis revealed a correlation coefficient of -0.845 for this filtered data. This indicates a strong negative correlation between maximum battery capacity and number of charge cycles.

A scatter plot and regression curve illustrate this relationship:

Source: Frandroid

This result shows that battery degradation is more pronounced when the initial capacity is no longer at its maximum. In other words, once the battery starts to degrade, the process speeds up with each additional charge cycle.

And Apple’s promise? 80% capacity up to 1000 cycles

Apple, since the iPhone 15, has promised 80% maximum capacity up to 1000 cycles, twice as much as previous generation iPhones.

Although our current data does not cover 1000 cycles, extrapolation of the current trend suggests that the maximum battery capacity could be well below 80% after 1000 cycles. Indeed, even for cycle numbers around 300-400, the capacity already falls below 90%.

Source: Frandroid

This casts doubt on Apple’s promise under normal usage conditions. However, there is nothing to indicate, for the moment, that the deterioration will not stagnate after a while.

The limits of this mini study

Note that our mini-study has several important biases. First of all, we don’t know the specific iPhone 15 models used. It is obvious that an iPhone 15 Pro Max, with a larger battery capacity, will require fewer cycles for comparable use compared to a standard model. This difference could influence the results observed.

Afterwards, we do not have information on user charging practices. Using fast chargers, using wireless charging (which can get hotter depending on the chargers), fully charging the battery from 0 to 100%, frequency of use, and leaving the device on charge overnight are all important. of factors that can harm battery health. These variables greatly affect the observed degradation.

We also don’t have any information about the environmentespecially since the outside temperature, humidity level and even altitude have a strong impact.

Recommended practices to extend battery life

To extend the life of their battery, one should adopt certain charging practices. One of the key recommendations is to Do not leave iPhone at 0% or 100% charge for long periods of time. Allowing the battery to completely discharge or constantly keeping it fully charged can accelerate its degradation. It’s better to keep battery charge between 20% and 80% to minimize stress on the battery cells.

Promote slow wired charging rather than fast or wireless charging is another beneficial practice. Fast charging can generate more heat, which can negatively affect battery longevity.

Likewise, Wireless charging may also cause an increase in temperaturee if the charger is not of good quality. Use a standard wired charger, preferably one supplied by Apple or certified by MFi (Made for iPhone), can help extend battery life.

It is also crucial to protect iPhone from extreme temperatures. Lithium-ion batteries, like those used in iPhones, are sensitive to very high or very low temperatures. Prolonged exposure to extreme temperatures can reduce battery capacity more quickly. Users should avoid leaving their iPhone in a hot car in summer or using it in very cold environments.

Finally, enable the battery optimization option in iPhone settings is a simple but effective measure. This feature, available in iOS, helps intelligently manage charging cycles by delaying fully charging to 100% until you need to use the device.

Source: Frandroid

For example, if you charge your iPhone overnight, it won’t fully charge to 100% until just before you wake up, reducing the time spent on full charge and minimizing stress on the battery.

You can also choose to limit the load to 80% maximumeven if it means deactivating this option when you are really on the move.

How to replace your iPhone battery?

If your battery is too degraded, several possibilities exist. First, know that any iPhone purchased new benefits from a one-year limited warranty, which covers manufacturing defects, including battery problems. If your battery has manufacturing defects and falls below its optimal capacity during this period, Apple will replace the battery at no charge.

If you have subscribed to AppleCare+, coverage is extended to two years from the date you purchased your iPhone. AppleCare+ also includes two accidental damage calls, for a reduced service fee.

Regarding the battery, AppleCare+ guarantees free replacement if the battery capacity falls below 80% of its original capacity during the coverage period.

If your iPhone is no longer covered by the one-year warranty or AppleCare+, Apple still offers a battery replacement service for a fee. Costs vary depending on the iPhone model. Prices are often updated, and they will be offered after a diagnostic stage of your battery: which can be done with the Apple Support application or directly in the Apple Store.


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