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How to choose a charger for your smartphone or other devices — everything about volts and amperes


Nowadays, more and more smartphone manufacturers are loudly broadcasting: “Our device supports 60 watt fast charging”, “We introduced a new charging standard – 80 watts!” Vivo went even further by releasing Super FlashCharge with 120 watts. This is certainly good as an engine of progress, but it is confusing for users. Let’s figure it out.


Physics 101 or “What is “slow” charging?”

The main indicator of the charger is the power it gives out. Let’s go back to fifth grade for a minute. The product of current strength (amperes, A) and voltage (volts, V) is power (watts, W), according to the formula W = I · U. Now let’s go back to real life, and what do we see? We see a sad picture – the vast majority of smartphone users do not understand this. Few people know the charging characteristics of their gadget. We will fix it.

Before delving into the variety of fast chargers, we’ll figure out what the standard, “slow” charging implies. The answer is simple – anything. There is no description of the technical standards for “slow” charging. Until 2013, when Qualcomm brought the Quick Charge technology to the masses, the chargers were simply charging, and after that they were divided into fast and not so fast.

Nevertheless, the standard is usually 5 V, with a current strength of 1.0, 1.5, 2.0 and 2.2 A, that is, from 5 to 11 watts. Everything above is classified as fast charge.

How to learn to understand your charger

We will develop our technical literacy and learn to understand the information that the manufacturer of chargers indicates. So, the charging label can tell us which modes this charger supports. Of course, if it is not made in a dark Chinese basement. We take two chargers that were laying nearby, and consider their capabilities.

How to choose a charger

Charger #1 (from Lenovo VIBE P1 Pro)

First of all, we will find the word “Output”, all that follows is the current and voltage parameters from the device. We look: 5.2V-2A, 7V-2A, 9V-2A, 12V-2A. Multiplying volts and amperes, we recognize four supported operating modes – 10.4 W, 14 W, 18 W, and 24 W. The charger can work slowly, to support outdated smartphones without fast charging, and has three fast modes.

Three power options are designed not for three different smartphones, but for one. The fact is that at a maximum value of 24 W, the smartphone does not charge all the time, but up to about 60% of the battery capacity. After it goes to 18 watts and so on downward. The point is to prevent the battery from overheating. After all, more power = more heat.

Charging # 2 (from Xiaomi Mi 9)

We see: 5V-2.5A, 9V-2A, 12V-1.5A. We learn the power – 12.5 watts, 18 watts and… 18 watts. This charger offers us a standard mode, and two equally fast 18 W modes. What for? Well, ask Xiaomi. As you can see, this charger is simpler, and has only two fast charging modes (in fact, only one).

Now let’s choose

We simulate the situation – you lose the charger, and you are standing: a) at the station, b) at the airport, c) in the middle of the room, with a confused look. We pull ourselves together, open the website of the manufacturer of your smartphone, enter our model and look at the charging characteristics. Have you found it? It should be something like: “Support for fast charging 40 watts.” It is also important to know the fast charging technology. For example – Quick Charge 3.0. Now you can start choosing the charger.


So, we know that the smartphone supports a maximum charge power of 40 watts. And we know that intermediate values ​​are also important – battery overheating, remember? Weed out all chargers not related to QC 3.0. Even if among other fast charging technologies (for example, Pump Express) we come across a device with the necessary characteristics, it is not a fact that they will make friends with our smartphone.

We have the remaining chargers with the technology we need. We choose. Let’s say the first one that caught our attention has a maximum power of 12V-2.5A. And this is 30 watts, not enough. We look further – 20V-2A, this is 40 watts, exactly what you need! We look at the intermediate values ​​and, if everything suits us, we buy it. If the charger’s power turned out to be higher than that supported by the smartphone, it’s okay, it won’t explode, the charger will just not work at full capacity.

About dishonest manufacturers and wireless chargers

It so happens that greedy manufacturers equip their smartphones with stock chargers. It often happens when the smartphone itself supports 25-watt charging, and the adapters that come with it support only 15 W or less.

wireless charger

In the case of a smartphone, we can add the “correct” charger. As before, we learn about the technology and select the most suitable device. For example, a certain Motorola smartphone comes with a 5V-5A charger, that’s 25 watts of power. The smartphone itself can be charged from 35 watts. We learn the technology, for Moto it is TurboPower 30. Ok, this technology supports chargers with 5V-7A, this is 35 W.

We will pick up a charger for a wireless dock. For example, we have a wireless “pancake” from Xiaomi. The characteristics on it are as follows: 5V-2A, 9V-1.6A, that is, 10 and 14.4 watts. By name we find it on the site, and check the technology used – Quick Charge 2.0. It remains to find the 9V-1.6A charger. Although Quick Charge 2.0 technology provides devices up to 12V – 2A, it makes no sense to overpay for them, the wireless station itself will not give out more than 14.4 watts.


As you can see, having understood the conversion of volts and amperes to watts, you can easily determine the output power of the chargers. When choosing a charger, focus primarily on the fast charging technology used in it. It is preferable to use the same technology in a smartphone.

Charging the smartphones

Then you need to pay attention to the power supported by the smartphone. It is enough to simply compare the characteristics of the smartphone and the charger, and then the choice of the latter will not be a problem.

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