Comparison power banks

The capacity of a powerbank indicates the amount of energy it can store and is usually specified in two formats in the specifications — mAh and Wh. The mAh value is more familiar to most buyers and helps quickly understand the class of the model, while Wh more accurately reflects the total energy reserve and is more convenient for a more accurate comparison of devices. For example, a powerbank with 10000 mAh usually has about 37 Wh, a model with 20000 mAh — approximately 74 Wh, and a version with 30000 mAh — about 111 Wh. The higher these values, the more charges for a smartphone, headphones, watch, or other devices can be expected, but the larger, heavier, and usually more expensive the device becomes. At the same time, it is important to remember that the actual output is always lower than the nominal figures due to energy conversion losses. Therefore, capacity is one of the main parameters that immediately shows whether the powerbank is suitable for a day's backup or for more serious autonomous use.

The real capacity of the power bank.

Real capacity is the amount of energy that a power bank is able to transfer to rechargeable gadgets. This amount is inevitably lower than the nominal capacity (see above) — most often by about 1.6 times (due to the fact that part of the energy goes to additional features and transmission losses). However, it is by real capacity that it is easiest to evaluate the actual capabilities of an external battery: for example, if this figure is 6500 mAh, this model is guaranteed to be enough for two full charges of a smartphone with a 3000 mAh battery and smartwatches for 250 mAh.

The capacity in this case is indicated for 5 V — the standard USB charging voltage. At the same time, the features of milliamp-hours as a unit of capacity are such that the actual amount of energy in the battery depends not only on the number of mAh, but also on the operating voltage. In fact, this means that when using fast charging technologies (see below) that involve increased voltage, the actual value of the actual capacity will differ from the claimed one (it will be lower). There are formulas and methods for calculating this value, they can be found in special sources.

The type of own batteries installed in the power bank. Lithium-ion(Li-Ion) or lithium-polymer(Li-Pol) batteries are most commonly used today. Other options are less common — solutions based on nickel-metal hydride(Ni-Mh) batteries, as well as on LiFePO4 type cells. In addition, a rather promising development has appeared relatively recently — graphene batteries; however, as of early 2021, they are just beginning to be introduced into mass production. Here are the main features of each of these varieties:

— Li-Ion. Lithium-ion technology allows you to create quite capacious batteries of small dimensions and weight. In addition, such elements are easy to use (the main operating parameters are regulated by the built-in controller), have a high charge speed and are practically not affected by the "memory effect" (reduction in capacity when charging an incompletely discharged battery). The main disadvantage of lithium-ion batteries is a rather narrow range of permissible ambient temperatures. This is not a problem in urban usage, when the power bank is used mainly indoors and is carried in a pocket or in a bag; but for less favorable conditions (such as long hikes in the cold season), it is worth choosing models with good thermal insulation. You can also find information that lithium-ion batteries are prone to fires and even explosions; however, this is usually due to...failures in the embedded controllers, and these controllers are also constantly being improved, and nowadays the risk of such an accident is so low that it can actually be neglected.

— Li-pol. Further development and improvement of the lithium-ion technology described above; the main difference is the use of a solid polymer electrolyte instead of a liquid one (hence the name). This made it possible to achieve even greater capacity without increasing the dimensions, as well as to reduce the potential for fires and explosions during abnormal operation. On the other hand, lithium-polymer batteries are somewhat more expensive than lithium-ion batteries and are even more sensitive to temperature disturbances.

— Ni-Mh. Nickel-metal hydride batteries are distinguished by their reliability and a wide range of permissible temperatures, however, with the same dimensions, they are inferior in capacity to lithium-ion (and even more to lithium-polymer) batteries, and they also require certain specific operating rules to be observed. In addition, it is worth noting that Ni-Mh technology is well suited for removable batteries. It is in this format that such batteries are most often used: power banks of the Ni-Mh format are usually adapters with slots for several replaceable elements of a standard size (for example, AA). In this case, usually, several corresponding removable batteries are included in the kit, however, if desired, they can be replaced with other elements — these can even be disposable batteries from the nearest store. Such an opportunity can turn out to be very useful if the power bank is out of juice at an unfortunate moment, but there is no way to charge it; in addition, worn-out batteries can be replaced with fresh ones without changing the entire device.

— Li-FePO4. Another modified version of the Li-Ion batteries described above, the so-called "lithium iron phosphate". The advantages of such cells over classical lithium-ion ones are, first of all, a stable discharge voltage (until the energy is exhausted), high peak power, long service life, resistance to low temperatures, stability and safety. In addition, due to the use of iron instead of cobalt, such batteries are also safer to manufacture and easier to dispose of. At the same time, they are noticeably inferior to the classic lithium-ion ones in terms of capacity, and they are more expensive, which is why they are rarely used.

— Graphene. Batteries based on graphene — a carbon film one atom thick. The battery itself consists of a set of such films, between which silicon plates are laid, and lithium cobaltate or magnesium oxide is used as an anode. This design provides a number of advantages over the earlier batteries described above. First, graphene technology provides a high charge density, which allows you to create capacious and at the same time light and compact batteries. Secondly, for the production of such batteries, fewer rare resources are needed than for the same lithium ones; and the production itself is more environmentally friendly. Thirdly, such batteries are not prone to overheating and explosions when overloaded or damaged. On the other hand, graphene power supplies take a long time to charge and are not durable. However, this technology is still developing, and in the future it is likely that these shortcomings will be eliminated — completely or at least partially.

The number of modern ports USB-C and built-in USB-C cables that can be used to charge smartphones, tablets, headphones, consoles, and other current devices. This format is particularly convenient today because USB-C has become the main connector for most new devices and usually supports higher charging power than USB-A. One USB-C output is usually enough for everyday use, while two and three are convenient if you need to connect several gadgets at the same time.

The number of USB-A ports available for charging smartphones, headphones, accessories, and other devices. This format is still in demand because USB-A is widely used and fits a large number of existing cables and devices, although it usually falls behind USB-C in terms of relevance and power. A single USB-A output is typically sufficient for basic everyday use, while two, three, four, or more are convenient for connecting multiple gadgets simultaneously.

The power capacity of the main USB-C port, which among USB-C connectors is typically the most powerful. This specification is especially important for smartphones with fast charging, tablets, portable consoles, and laptops that require increased power supply.

Values around 18 – 30 W are usually sufficient for fast charging smartphones, 45 – 65 W are suitable for portable consoles, some ultrabooks, and other more demanding devices, and 100 W and above are even designed for powerful laptops and heavy loads.

Maximum output power of the second USB-C port, which usually lags behind USB-C1, but can still be suitable for fast charging smartphones, portable consoles, and other modern devices.

The power on the USB-C3 port indicates the maximum power with which the power bank can operate through the third USB-C port, which is more often used as an additional output for less demanding devices or for simultaneous charging of multiple gadgets. It is worth noting that simultaneous charging on multiple ports reduces the maximum power output.

The power on USB-A1 port shows the maximum output power of the main USB-A port, which among USB-A connectors is usually the most powerful. Values around 10 – 18 W are typically sufficient for regular or fast charging of smartphones, 22.5 – 33 W are already interesting for faster charging of compatible models, while higher values for USB-A are significantly rarer than for USB-C. Compared to USB-A2, USB-A3, or USB-A4, it often makes more sense to connect the most demanding device to USB-A1 if maximum speed from this type of port is needed.

However, the USB-A format itself is already less promising today than USB-C, so such a port is more often used for smartphones, headphones, watches, speakers, and other mobile devices rather than heavy-duty applications like laptops.