Battery capacity
The higher the battery capacity, the more energy the power bank is able to accumulate and then transfer when charging to gadgets connected to it. But it should be borne in mind that not all of the accumulated energy goes specifically to charging – part of it is spent on service functions and inevitable losses in the process of transmission. So in the specifications, the real capacity of the power bank is also often specified. If there is no data on real capacity, then when calculating it is worth proceeding from the fact that it is usually somewhere 1.6 times lower than the nominal one. For example, for a model with a nominal capacity of 10,000 mAh, the actual value will be approximately 6300 mAh.
As for the specific values of the nominal capacity, then in models with the lowest performance it is
5000 – 7000 mAh and even
less ; such power banks are suitable as a backup source of energy for 1 – 2 smartphone charging with a not very capacious battery or other similar gadget. The
10,000 mAh solutions are the most popular nowadays – in many cases, this option provides the best price-capacity ratio. The
20,000 mAh and
30,000 mAh options are also very common. But even a capacity of
40,000 mAh or
more, thanks to the development of modern
...technology, is quite common.Real capacity
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.
Charge cycles
The number of charge-discharge cycles that the battery can withstand without significant loss of performance.
During operation, batteries wear out, and because of this, their specs (primarily capacity) noticeably deteriorate. Battery life is usually measured in charge-discharge cycles. The features of counting cycles are described in detail in special sources, but here we note that not always models with the same claimed resource turn out to be equally durable in fact. The fact is that different manufacturers may understand “significant loss of performance” differently: for example, one brand can indicate a resource up to a 20% decrease in capacity, the second — up to a 60% decrease. Therefore, when choosing, it makes sense to focus not only on pure numbers, but also on other sources — test results, reviews, etc.
Also note that battery life can be noticeably reduced if the operating conditions are violated — for example, in case of overheating or excessive cold.
USB A
The total number of
USB-A ports for charging connected gadgets. This type is gradually being replaced by USB type C, however, most models still use USB-A as the main output. This is also indicated by the number of corresponding ports. Classic are
2 USB-A outputs. However, there are also compact
models for 1 output, and more impressive ones with
3 and
4 USB-A(even more).
Max. power (per 1 port)
The maximum power that the power bank, theoretically, is capable of delivering to one rechargeable device. Usually, this power is achieved under the condition that no other device is connected to the battery (although exceptions to this rule are possible). And if you have ports with different charging currents or support multiple fast charging technologies, this information is given for the most powerful output or technology.
For modern power banks, a power of
10 watts or less is considered quite low; among other things, it usually means that the device does not support fast charging. Nevertheless, such devices are inexpensive and often turn out to be quite sufficient for simple tasks; Therefore, there are many models with similar specs on the market. The power of
12 – 15 W is also relatively small,
18 W can be called the average level,
20 – 25 W and
30 – 50 W is already considered an advanced level and in some solutions this parameter may
exceed 60 W.
In general, higher power output has a positive effect on charging speed, but in fact there are a number of nuances associated with this parameter. Firstly, not only the power bank, but also the gadget being charged should support the appropriate power — otherwise the speed of the process will be limited
...by the specs of the gadget. Secondly, in order to use the full capabilities of the power bank, it may be necessary for it to be compatible with certain fast charging technologies (see "Fast Charging").USB type С
USB type C is a popular type of USB connector characterized by its small size, reversible design, and fairly advanced (in theory) capabilities. If there are several connectors of this type, the first one is considered to be capable of delivering more power.
It is characterized by the rated power supplied by the power bank when a load is connected to the first or only
USB type C output and the current strength. The speed of the charging process directly depends on the power. It is traditionally calculated by multiplying the current by the voltage; However, the standard voltage for USB power is 5 V, so current is considered to be the main indicator of power.
The magnitude of the charging current directly determines the power supplied to the device being charged - and, accordingly, the maximum speed of the process (in practice, it may be lower if the device being charged has strict restrictions on the charge current). Power is also determined by the supply voltage (the number of watts is calculated by multiplying amperes by volts); While the standard USB output voltage is 5V, many fast charging technologies (see below) use higher voltages. Therefore, in the notes to this paragraph, the maximum power on the USB type C connector is also indicated.
As for specific values, the most popular option for USB type C outputs in modern power banks is
3 A. There are also other values - both sma
...ller ( 2.4 A, 2.1 A and 2 A) and larger ones - but noticeably less frequently.USB A
A standard
USB A port is characterized by the rated power supplied by the power bank when a load is connected to the first or only USB A output and the current strength. If there are several connectors of this type, the first one is considered to be capable of delivering more power.
The speed of the charging process directly depends on this indicator. Power is traditionally calculated by multiplying current by voltage; However, the standard voltage for USB power is 5 V, so current is considered to be the main indicator of power.
The charging power and, accordingly, the speed of the process depend on the current strength. Nowadays, on USB ports, a current of
2 A or
2.1 A is considered basic and quite modest,
2.4 A and
2.5 A are average,
3 A and
more are noticeably above average, and certain fast charging technologies allow you to achieve values of
4 A. 4.5 A and
5 A. However, it is worth considering that to operate at high current, such an opportunity must be provided not only in the power bank, but also in the gadget being charged. So when purchasing a model, it doesn’t hurt to check whether the devices being charged suppo
...rt high charge currents.
It is also worth noting two nuances associated with the presence of multiple USB charging ports. Firstly, they may differ in the current they produce. This allows you to select the optimal connector for each device: for example, to quickly charge a tablet with a capacious battery, it is desirable to have a higher current, and a device with a low charging current can be connected to a “weaker” port, so as not to create unnecessary load on the battery and controller. The second caveat is that if all USB connectors are used simultaneously, the current supplied by each of these connectors may be lower than the maximum; in other words, not all power banks allow you to simultaneously use USB ports at the maximum possible power. You can understand whether such a possibility exists by looking at the charge power (see below); if the charge power is not indicated, you should refer to detailed documentation from the manufacturer.Power bank charge current via USB
Nominal charge current supported by the power bank when charging its own battery via microUSB, USB type C, or Lightning (see "Battery charging inputs").
This is the maximum and, in fact, the recommended power bank charge current. If the amperes supplied by the power source exceed this value, the charge current will still be limited by the built-in controller to avoid overloading. And using a charger with a lower output current, in turn, will lead to an increase in charging time.
Data on the charge current via USB (Lightning) is especially important due to the fact that modern power banks are usually not equipped with their own chargers for these inputs, and energy sources must be separate. On the other hand, if a high charging speed is not critical for you, you can ignore this parameter: any USB connector is suitable as a power source for the corresponding power bank inputs.
Power bank charge power
Nominal power supported by the power bank when charging its own battery through the appropriate interface. See "Battery Charging Inputs" for details.
