Batteries Global Blog

There is no need to discharge a lithium-ion battery to 0% from time to time, contrary to the practice that prevailed with certain older generation batteries. It is even now not recommended: this type of battery degrades more quickly when it drops below 20% charge, a “danger zone” to be avoided as much as possible. The chemistry of a current smartphone battery perfectly supports frequent charges, it can be recharged often. However, it is not recommended to recharge it as soon as the opportunity arises, because its comfort zone is between 30% and 80% charge. It is also better to wait until the gauge of your smartphone drops to 25 or 30% before plugging it in.

Avoid high temperatures

Modern smartphones are equipped with lithium-ion batteries, designed to be used between approximately 10°C and 30°C. When they are exposed to higher temperatures for a long time, they degrade more quickly. It is better to avoid placing a smartphone in direct sunlight, especially when it is charging. The worst overheating scenario combines sun, recharging, and demanding use: “when using your smartphone as a GPS over a long distance for example”, warns Olivier Simon. Or when you play with your smartphone while recharging it.

Since our skin temperature is high, especially in summer, it is best to avoid carrying a smartphone in tight pants or in the inside pocket of a coat. Conversely, in the heart of winter, when temperatures fall below 0°C, it is advisable to wear your smartphone close to your body to slow down battery wear.

As we have seen, iOS and Android optimize the use and recharging of the battery as well as possible. The fact remains that it is possible to increase its lifespan by respecting a few basic rules.

Preferably recharge the battery when it indicates between 20 and 80%. Do not wait for it to drop below and recharging beyond 80% damages your battery.
Unplug your smartphone when the gauge indicates 100%, or even before.
Avoid using your smartphone when it is charging. Playing games, using a GPS app, making calls or leaving the terminal in the sun increases its temperature while recharging does the same, which damages it.
If you don’t need Bluetooth, wifi or geolocation, turn them off, because the device constantly and automatically checks for updates and launches constant requests that are very energy-consuming to do so.
For the same reasons, prefer a wifi connection to 4G/5G if possible.
Use the original charger provided/sold with your smartphone or recommended by the manufacturer (designed to optimize speed and optimal charging power for the model).
Consider using Android’s dark mode if you have a smartphone with an Oled screen.
Use auto-brightness to adapt the screen backlight to the mood.
Finally, to save your battery, the first instinct is quite logically to activate the energy saving mode on your smartphone. The smartphone will then limit access to data from apps that are not in the foreground and will pause the GPS when the device screen is off.

In this race for autonomy, who is the best? “On consumption in use, Apple and its iPhones are ahead with six devices in our Top 10”, points out Olivier Simon. Apple masters both the hardware design and the operating system, so it’s easier for this computer giant to optimize battery usage. “With a smaller battery, Apple does as well as an Android terminal with a higher battery capacity,” adds the DxOMark expert.

As often, the marketing figures displayed by brands do not make much sense. Thus, indicating the capacity of a battery is limited information that only gives a vague overview of the autonomy that can be expected from a smartphone. “It’s as if you indicated the volume of a car’s tank without taking into account the characteristics of consumption”, laughs Olivier Simon. Our autonomy tests therefore still have a bright future ahead of them.

However, the iOS and Android operating systems manage search and battery usage better and better. A few years ago, Sony took into account the morning alarm to adapt the recharge to 100% a few minutes before. A strategy widely adopted by other manufacturers. Google has greatly improved its operating system, especially since version 9 Pie.

In the past, the various manufacturers offered techniques to kill apps in the background in order to limit consumption, but this era is now over. We now know that relaunching a service ultimately requires a lot of energy. With embedded machine learning, which goes by the sweet name of Auto Awesome Battery, Android is now able to analyze the use made of applications to optimize their use. “No need to kill WhatsApp in the background if it is used every 5 min”, details our interlocutor. Another example, Android is able to know, by interrogating the gyroscopes of the mobile, if there has been a physical movement or not and to “prohibit in the latter case a request for geolocation costly in energy made by a running application” .

On how to recharge your batteries, the results are more in line with our expectations. Thus, you are 60% to recharge your mobile as soon as the battery is less than 20%, which is a good reflex to limit wear. Indeed, as Olivier Simon explains, batteries degrade more quickly when the voltage is very high (charge level above 90%) or very low (below 20%). It is therefore preferable to multiply short charging cycles rather than letting your smartphone discharge completely.

Conversely, leaving your mobile plugged into a power outlet when it is at 100% battery will gradually degrade your battery. In question, “small overvoltages applied by the charger to the battery, which is already at its maximum voltage to maintain the level”, specifies Olivier Simon. These overvoltages affect the quality of the battery, whether you charge your smartphone in wired mode or by induction. Also note that it is better to charge a cold battery and, on the contrary, to use your smartphone at the right temperature.

Everything for autonomy!

According to our survey, you are a huge majority — 92%! — to prefer good battery life to fast charging of your smartphone. A more than clear-cut opinion which, let’s face it, surprises us a little. Indeed, a few years ago, batteries had a ridiculous autonomy and fast charging was just wishful thinking. Today, the situation has clearly changed. The autonomy of a smartphone is generally more than correct and the fast charge very effective in saving time. We thought (wrongly therefore) that fast charging would be a more important criterion for you. It may suffer from a bad reputation, that of weakening the health of accumulators.

Beyond the power of the chargers, it is the voltage that must be taken into account. “The higher the voltage of a charger, the more complicated it is for the battery to manage, underlines Olivier Simon. Today, manufacturers try to apply the highest amperage with the lowest voltage, and thus increase the durability of the batteries”. For the moment, no study comes to corroborate these statements.

DxOMark is currently working on the subject and the case will be followed up in 2022. However, to benefit from efficient fast charging, it is advisable to use the charger offered by the manufacturer, because beyond the power delivered, the chargers communicate with smartphones to optimize charging. Communication that can be complicated, if not impossible, with a “classic” charger. A smartphone that accepts fast charging up to 66 W can thus very well limit the power to 10 W with the latter. “It’s often for security reasons, explains Olivier Simon. The faster the charge, the more the phone will ask to know what it is using for charging. Sometimes, it will have to be able to recognize the charger, but also the cable to be sure to pass a high amperage without taking any risks.”

No matter what your charge indicator says, your device will never actually be 100% charged or completely discharged. It is the software integrated into the phone that manages these problems. The most useful advice to preserve your battery is therefore to charge your phone on long fixed beaches in order to avoid small deleterious recharges. If you need a little boost during the day, fast charging up to 80% with a high-performance charger (provided the phone is compatible) will not damage your device, however. This will allow you to focus on habits with more concrete results.

In addition, lithium-ion batteries hate high temperatures. It is therefore advisable not to leave your phone in the sun, especially in summer, or charging in cramped places, such as under a duvet… For the same reason, and also because a battery does not like to be charged and stressed at the same time, avoid using your phone when it is plugged in. A lithium-ion battery is supposed to last about 500 charge cycles before losing efficiency irreparably. By adopting these simple reflexes, it is possible to go much further.

To understand how to optimize the life of your battery, you have to have in mind, very schematically, how a lithium-ion battery works. During charging, the anode (the + pole) will receive and accumulate electrons from the lithium placed at the cathode (the – pole). The current from the recharge somehow “rips” the energy present in the lithium. When the battery is no longer connected, the electrons will want to go the other way, which will produce the electric current. The fewer electrons left at the lithium level – i.e. the closer you get to the maximum charge – the more strain the battery is subjected to.

This is why it is accepted that the optimal recharge range for a lithium-ion battery is between 20 and 80%. In theory, it is therefore recommended to keep your phone within this range. This would mean that you have to recharge your smartphone as soon as it drops below 20% and disconnect it beyond 80%. In practice, it is more complicated. It is much more harmful to repeat recharges than to carry out a complete charge. Also, manufacturers have integrated technical limitations for several years.

The increase in the definition of screens, the increased frequency of chips and memory, or even internet connectivity require increasingly high-performance batteries for smartphones. Manufacturers are well aware that this criterion is essential for all buyers today, especially at a time when high-end models flirt with the thousand euros, or even exceed it. However, the technology embedded in current accumulators has not evolved for a long time. To increase the capacity, no secret: you have to increase the size of the battery. But smartphones are also judged on their thinness and weight.

The gains in autonomy and durability are therefore to be found in the optimization of daily use. The latter is already at the heart of the concerns of engineers, who are trying to reduce the consumption of chips and the greediness of operating systems. On the user side, it is at the level of daily reflexes that we must work.