Comparison Ugreen PB761 vs Borofone BJ63A Nimble

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 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.

The total charge power provided by the power bank on all connectors overnight - when devices are connected simultaneously to all charging ports.

This parameter is given due to the fact that the total charge power does not always correspond to the sum of the maximum powers of all available ports. The built-in battery of a power bank often has its own limitation on the output power. Therefore, for example, in a model with two 18 W USB ports, each total charge power can be the same 18 W. Note that the distribution of power among the connectors may be different: in some models it is divided equally, in others it is divided in proportion to the maximum current strength (if it differs on different ports). These nuances should be clarified using the detailed characteristics of the charging connectors.

If you plan to regularly use all power bank connectors at once, you should pay attention to this indicator.

The power in watts at which the power bank is charged under normal conditions.

The higher the charging power, the less time it takes to charge (given the same battery capacity). For example, fast charging of a power bank typically means a charging power of 30W or more. However, this parameter does not directly affect compatibility with charging devices: modern portable batteries can work with chargers of both higher and lower power. In the first case, the battery controller will automatically limit the charging current, while in the second case, charging will simply take more time.

The time required to fully charge a battery discharged “to zero”. Features of the charging process in different models may be different, respectively, and the time required for this may differ markedly even with the same capacity.

Fast-charging batteries tend to be more expensive. Therefore, choosing this option makes sense if you do not have much time to replenish your energy supply — for example, for hiking. However, keep in mind that charging at full speed may require a charger that supports certain fast charging technologies (see below).

It must also be said that in most modern batteries, the charging speed is uneven — it is highest at the several first percent from zero, then gradually decreases. Therefore, the time required to replenish the energy supply by a certain percentage will not be strictly proportional to the total claimed charge time; moreover, this time will depend on how much the battery is already charged at the time the procedure starts. For example, charging from 0 to 50% will take less time than from 50 to 100%, although both there and there we are talking about half the capacity.

Types of cables and/or adapters for charging external devices included with the power bank.

The type of these cables is indicated by the plug used to connect to the charging gadget; the connection to the power bank itself is usually through a standard USB-A or USB type C output. It should be emphasized that this refers to removable cables/adapters; types of built-in charging cables are specified separately (if available — see below).

Overall, this parameter allows you to assess the capabilities of the power bank available "out of the box," without purchasing additional accessories. As for specific interfaces, most external batteries these days come with cables/adapters for microUSB, USB type C, and/or Lightning; more specific connectors are extremely rare. Here are the features of the most popular options:

— microUSB. A connector extremely common in modern portable gadgets. It is less convenient than the newer USB type C and has fewer working characteristics, but it still maintains popularity.

— USB type C. A relatively new standard for miniature USB connectors, used for charging both in portable devices and larger ones — particularly some ultra-compact laptops. Physically, it differs from microUSB with slightly larger sizes and a reversible design, allowing the plug to be connected in either direction. In terms of performance, USB...type C is notable for better compatibility with fast-charging technologies: more such technologies can be used with it, and Power Delivery was originally designed for this connector. However, having a USB type C cable does not necessarily mean support for fast charging.

— Lightning. A standard proprietary connector used in compact Apple gadgets; such technology is not found with other manufacturers.

Note that if several types of included cables/adapters are specified in the characteristics, the specific format of such accessories may vary. For example, the "microUSB plus USB type C" option could mean two separate cables, one cable with two plugs, a cable with one connector plus an adapter for another, etc.