Power Bank: how it works

What is a Power Bank

To begin with, let's try to understand what exactly a Power Bank is. These are essentially those devices that allow you to recharge various devices, such as smartphones, tablets, smartwatches, laptops and so on, in any place and in any circumstance. They are therefore gods portable external batteries equipped with one or more USB ports to connect the devices to be charged.

They can have various shapes (generally they are a "soap" or "tube") and various capacities and are usually quite small in size so as to be easily transportable, for example in a pocket or backpack, so as to be able to take them out at the first good occasion.

However vast and varied the Power Bank market may be, it is however worth emphasizing that not all of them are created with the same quality and safety standards, which is why it is always necessary to pay particular attention to what you buy and above all to the presence of any chip on the same able to control the charger and prevent the devices connected to it from being overloaded and damaged. It is therefore not so difficult to deduce that to avoid various problems it is good practice to stay away from the so-called cinesate.

As for the purchase, it can be made in stores and chains of electronic and computer items in general as well as online, on e-commerce websites such as Amazon. Their cost, which varies depending on the capacity, the form factor as well as all the other technical characteristics, starts from 10 euros but can even exceed 100 euros. If you want some advice for purchases, you can consult my guide on the subject.

Using the devices in question is very simple, just connect with the "usual" cable the device that needs to be recharged to the USB socket of the portable battery and you're done. When charging is complete, it is then possible to disconnect the device from the Power Bank socket just as is generally done with the common electrical socket. That's all.

Technical features

Having understood what exactly a Power Bank is, let's now pass through the main technical characteristics (some of which have already been mentioned in the previous step) of the devices belonging to the category in question. For more info, keep reading, you will find everything explained below.


Capacity is one of the main technical characteristics of Power Banks and is calculated in milliampere machine (mAh), like that of the batteries of smartphones and tablets, which corresponds exactly to the thousandth part of an ampere / hour, the unit of measurement that is used to indicate the number of amperes (which is the unit of measurement of the intensity of electric current ) that goes through a device every hour. Only in some cases the capacity of the Power Banks is expressed in watt-ora (Wh).

The choice of the capacity of the Power Bank (which you find indicated quite clearly on the device itself or on its sales package) varies according to the type of device to be recharged as well as the amount of recharges to be made. You must therefore first identify the capacity of the battery you want to recharge, which you can easily find out by doing some research on Google as well as by taking a look at the sales package of the reference device.

However, keep in mind that the number of mAh indicated for the various Power Banks cannot be directly related to that of the batteries to be recharged, since it is almost always expressed on the basis of a voltage of 3.7V, which is the voltage of the battery, and not on the voltage of 5V, which instead is the voltage used for charging smartphones, tablets and other devices. To obtain the Wh value compatible with that of the devices to be recharged, it is necessary to divide the value by 5 (i.e. 5V), then [Wh number] / 5.


As anticipated a few lines above, depending on the model chosen, the Power Banks can be equipped with one or more ports of output and therefore allow to load a number of devices simultaneously which is variable as they vary. Most of these ports are of type USB A (the very common USB ports) and allow you to recharge the vast majority of smartphones, tablets and other devices, but there are also USB Type-C which are used to charge the most recent smartphones, some laptops and some video game consoles.

There is also at least one port on the Power Bank input, which allows you to recharge the portable charger itself. The ports in question are generally of type microUSB or, only in some cases, of type lightning (from Apple) that allow you to recharge the Power Bank using the same cable used for iPhone and iPad.


Each port of a portable charger can deliver a different amount of energy that is measured in Amps (A) and affects device loading times. In order for charging to take place as quickly as possible, it is essential that the target device is also compatible with the power level of the portable charger. In any case, the Power Banks are able to automatically identify the devices connected to their doors and then draw an adequate amount of energy for them without ever going further.

Another thing to bear in mind is the fact that when two or more ports are used simultaneously on the same Power Bank, the overall output power is divided between the latter.

In all cases, there is no risk of overloads or short circuits, at least by not buying quality products or in any case avoiding items of dubious origin, as anticipated a few lines above. This is because today almost all Power Banks have a safety system that interrupts the supply of energy in case of problems.

Fast charge

Many of the Power Banks currently on the market are also compatible with the technology QuickCharge which allows you to charge Android devices which in turn support it at the highest possible speed.

In case you don't know, the one just mentioned is a proprietary technology of Qualcomm (a well-known manufacturer of smartphone processors) which, using a system of dedicated voltages and amperages managed by the processor, allows you to recharge the battery of the device extremely quickly. of reference.

As for non-Android devices, such as the recent generation iPhones, the QuickCharge system is not supported but the possibility is still offered to perform rfaster charges as the output power of the Power Bank being used varies. In any case, while connecting a device that does not support QuickCharge to a portable charger that supports it, there is no risk as, in this case, the recharge will be performed in a normal way.

How to use it to charge other devices

So far all clear? Yup? Good. Then I would say that we can take the real action by going to find out how a Power Bank works, concretely, to recharge the other devices. However complex it may seem, in reality it is of a disarming simplicity. In fact, just turn on the charger by pressing on the affix on / off button and connect the device to be recharged (eg smartphone) to one of the USB sockets of the Power Bank using the original cable of the same (or in any case a certified cable in good condition) and it is done.

If the portable charger you are using has no on / off button then there is no need to press anything. The device will come into working mode automatic once connected to your smartphone, tablet or whatever else you want to recharge.

If the Power Bank used offers more USB ports and therefore allows you to recharge multiple devices at the same time, it is also possible to connect other devices to the same. Clearly, by doing so, the Power Bank charge will be exhausted before its due and depending on its capacity it may not even be able to fully recharge one or more of the connected devices.

The Power Bank will therefore begin to recharge the battery of the connected device (in the case of portable chargers equipped with indicator lights this is also signaled by their switching on and / or their flashing) and the device in use will show thecharge status indicator, if it is a device that generally provides this information, of course.

The timing to complete the charging cycle of the devices connected to the Power Bank varies according to the device in use as well as to the type of technology supported by both the portable charger and the device being recharged. In any case, once recharging is completed, any indicator on the device to be charged will signal the fact, any lights on the Power Bank will go off or in any case will indicate that the procedure has been completed and the transmission of energy from a device to the other will be interrupted, similarly to what happens with recharging via an electrical socket.

At that point, you can disconnect your devices from the Power Bank by removing the ends of the connection cable from the USB sockets of the portable charger as well as from the connected devices. If your Power Bank also integrates an on / off button, press the latter to turn off the device.

How to recharge the Power Bank

In an article on how a Power Bank works, it is practically essential to also talk about recharging the device itself. So let's see how it should be done, it's very simple, don't worry.

To do this, all you need to do is connect the portable charger to the power outlet using the power outlet USB cable charging unit attached to the sales package of the device and theadapter (usually the latter is also finished coupled with the Power Bank but otherwise you can buy it separately, for example on Amazon). You have to insert the larger end of the cable into the adapter and then insert the adapter into the wall socket, while the smaller end is connected to the Power Bank, in the appropriate port.

Then leave the Power Bank charging for as long as necessary, this is signaled to you by bright LEDs present on the same or, if not available, you can check the time required to complete the operation by looking at the relevant one user manual. However, keep in mind that in principle it takes about a couple of hours.

As an alternative to the procedure just written, you can recharge your Power Bank by connecting it to one of the USB sockets of yours computer, always using the special cable.

When charging is complete, regardless of whether you have used the wall socket or the computer, disconnect the Power Bank from the power source by removing the relative cable from the latter and from the device.

To make sure that the charge has taken place correctly, you can also connect your smartphone or tablet or any other device that you intend to recharge to the Power Bank on the fly so as to verify that the latter comes into operation and is able to deliver power.

Power Bank: how it works

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