We say it’s partly Apple’s fault, but really it’s also electric cars’ fault. If you have an iPhone, you will see that the default battery charging mode is to fill it up to 80%, and then not charge it to 100% until the last few minutes depending on your habits. In the Apple Watch it goes further, and normally unless you configure it differently, the battery will only be charged up to 75 or 80%. The same thing happens with electric cars, they “recommend” charging them only up to 80%, so then, why have a battery with a certain capacity if you don’t fill it later? Let’s explain it.
The 80% rule
Like many technology enthusiasts, you probably have several wireless devices… your cell phone, headphones, keyboard and mouse, a smart watch, etc. And all of us enthusiasts always want to take care of our devices, and when it comes to wireless devices, this means trying to make the battery last as long as possible.
A popular belief states that you must follow the “80% rule”, and the logic is simple: avoiding the “effort” of a full charge and keeping the battery within the so-called “golden zone” that includes 20 to 80%. %, the wear and tear of the battery cells is reduced.
Obviously, this implies a problem: the battery of the devices lasts less, especially if you do not allow it to drop below 20%, which greatly limits its use and, in many cases, makes the device lose its meaning… why have some wireless headphones if they can’t last a whole day of gaming? Let’s not talk about a laptop, whose battery life is much less.
Does charging the battery to 100% really reduce its useful life?
In order to answer this question, we must first study how charging a battery works. A battery is a device in which chemical energy is converted into electricity, in the case of computing devices, storing the energy in a lithium core (in other batteries, such as lead-acid batteries in cars, it is stored in a liquid solvent).
When the batteries are connected, the electrons inside begin to move and a chemical reaction begins inside that causes the release of excess electrons in the form of electricity. These electrons move through a wire or device and then usually re-enter the battery at the other end. Therefore, a battery can be considered a container with two compartments: one with an excess of electrons and another with a deficit of electrons. Due to the negative charge that the electrons themselves have, they are repelled in the first compartment, and are pushed through a cable or device ending in the second compartment.
Of course, a battery is not as simple as we have described above (above we have rather described the behavior of a cell), but the basic movement of the electrons is the same, and it helps to understand that if we reverse the flow of the electrons , the battery is recharged. By plugging the battery into a power outlet, the flow of electrons is forced back to the first compartment, again creating a surplus of electrons. Then we say that the battery is charged, and ready to go through the initial “discharge” process that serves to power the devices.
But of course, this would be under perfect conditions, and the real world is not. In the real world, energy efficiency is never 100%, and energy is lost in the form of heat, etc. In addition, there is a chemical reaction inside the batteries, and you can imagine that the chemical process that we have explained to you is not 100% efficient either, so some wear occurs.
The fact is that this wear is produced by the chemical reaction, whether the battery is at 10, 50, 80 or 100%. It doesn’t matter what level of “charge” it has, if we are extracting or introducing energy, wear occurs (the famous charging cycles), and therefore the belief that it is better to charge the batteries to 80% is quite inaccurate. It is true that there may be other derived problems, but they have nothing to do with the useful life of the battery.
In short: charge the battery to 100% and thus you will always have the maximum capacity of your device available. Don’t worry that this will reduce durability, because although it is true that it reduces it, the effect is practically negligible.