Insight: How should I best recharge iPhones? How to avoid battery damage?

In this article we answer the most common questions we receive about the battery and also dispel some myths

We often get messages asking us what is the best way to recharge an iPhone, if using a charger that is too powerful can damage the battery or if, on the contrary, it is too slow to cause damage. Today we want to clarify the matter once and for all.

The most important factors for not compromising a battery are basically 2: use cables and chargers designed with high standards, approved by the relevant bodies and therefore safe. Among these, of course, there are the original Apple products but also many other third-party products. If you are really not an expert, just rely on well-known brands (like Anker to name one) or those you read about on the iDeviceCareGh blog and avoid all those brands with a very strange or unpronounceable name but above all those that are sold at a particularly low price.


The iPhone 12 are sold with a Lightning to USB-C cable and therefore the best way to recharge them is with this cable, to which you will have to combine a charger that, of course, supports USB-C input.

If the iPhone 12 isn’t your first iPhone, no one forbids you to use a Lightning to USB-A cable you already own. This will in no way compromise the charging or the health of the battery for a long time. Use one or the other indiscriminately.

20W, 36W, 12W or 5W charger?

Having established that you can use any type of Lightning cable as long as it is genuine and safe (made by Apple or certified companies), let’s move on to the charger. As for the iPhone 12, these smartphones support faster charging, therefore Apple recommends using the 20W USB-C charger which must be purchased separately, but this does not prohibit you from using others.

In fact, iPhones are able to control the flow of energy they receive and as regards the iPhone 12, the maximum charging speed they can “accept” is about 22W. It follows that using a 30W or 50W charger will not make any difference: the charging times would remain completely unchanged because the iPhone would continue to accept its share of energy without ever going further.

The 20W charger can recharge the battery up to 50% about 30 minutes and even if they are those recommended for iPhone 12, nothing prevents you from using a 5W charger , like those supplied with previous iPhones. Of course, with a charger like this, the charging times get longer but in no way will you harm (or benefit) the battery. With such a charger, it will take 3 to 4 hours for a full charge.

Choosing between a 5W and a 20W charger should not make you worry about the health of the battery: neither of them will damage it and neither of them will have an advantage over the other in use. There is a small clarification to do about it and you can find it at the end of the article.

A 5W however, is just fine as a “bedside” charger and you could keep it fixed in the bedroom to recharge your smartphone during the night. If you also have other more powerful ones, then maybe you could use those during the day, when you need to recharge your phone faster.

Wireless charging

IPhones that support wireless charging can be charged with any dock that supports the Qi standard. Similarly to wall chargers, even in this case no matter what the maximum power of the base is, the iPhone will always recharge at the maximum speed of 7.5W.

This is a rather low speed but it allows you to keep the iPhone in a safe situation, avoiding overheating and damage to the battery. Apple works precisely on optimizations that make life easier for users. For this reason, with an iPhone, you will not have to worry about anything: you can place it on the base and it will himself avoid problems, accepting a limited amount of energy compared to what could be provided by the charging device.

The iPhone 12, and only them, thanks to the magnets and MagSafe technology, can reach a maximum speed of 15W when recharged with original Apple MagSafe chargers. With MagSafe chargers from other companies they won’t reach 15W but stop sooner.

Again, charging an iPhone at 7.5W will not make the battery last longer than charging it at 15W or 20W. The only thing that will change will be the charging times.

What harms the health of the battery?

The determining factor concerns the amount of energy contained in the battery . This deteriorates when it remains charged at 100% for too long and is maintained in this state even after reaching the maximum charge: that is to say that it is wrong to keep the phone charged for too long beyond what is necessary. During that period, in fact, it will only stop, discharge and drop to 99% and then immediately return to 100%, stop, and so on … in a continuous loop that puts her under strain.

It is for this reason that you often hear people say “ with a 5W charger the health of the battery stays high for longer” .In reality this sentence is true but it is also not true. It is wrong to attribute credit to the 5W because it is not these chargers that perform the miracle. As we have seen before, 5W or 20W makes absolutely no difference. The only thing that changes is using a 5W charger the phone takes longer to reach 100% and consequently if we imagine sleeping 7 hours a night, the battery will remain “completely full” for only 3 hours after which we will get up and disconnect it. from the current. With a 20W charger you reach 100% in an hour and then the battery remains charged even when it is already fully charged for about 6 hours, double the time. This is the “wrong” part.

To prevent all this, Apple has integrated a function within iOS that tries to understand the habits of users and to quickly recharge the first part of the battery and then stop completely and let the last 20% recharge only shortly before the time when the alarm goes off or we usually get up. This tool is really very useful but it does not always work very well as it is based on artificial intelligence that cannot accurately establish every situation in our life .. let’s say that it is much more suitable for those who always carry the same pace and the same habits . In all other cases it will be you who will have to be careful not to keep the phone charging for too long after reaching the maximum threshold.

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