Voltage
Rated voltage of a fully charged battery or a fresh battery. The practical value of this parameter may differ slightly from the nominal one, however, in the design of most electronics models, this feature is usually taken into account, and the user himself does not need to worry about this. And in general, voltage data in most cases does not play a key role and is more of a general reference information. This is due to the fact that all sizes (see above) have requirements not only for the overall design of the battery, but also for its voltage. Therefore, it is necessary to pay special attention to this indicator mainly in specific cases, such as searching for interchangeable elements or assembling a home-made electrical circuit and selecting power for it.
Maximum discharge current
The maximum discharge current provided by the battery is the maximum current that the battery can deliver without the risk of overloading, overheating and other troubles. This indicator directly determines compatibility with a specific device: the current consumed by the load must not exceed the maximum battery discharge current.
The maximum discharge current is indicated only for rechargeable batteries (see "Type"). By definition, it is greater than the nominal one (see above), but it is worth recalling that when the rated current is exceeded, the voltage at the battery output decreases. Therefore, in some cases, it is necessary to choose a battery exactly according to the rated discharge current.
Charge cycles
The number of charge cycles that the battery can withstand without noticeable deterioration in performance.
The charge cycle refers to the period of time from one complete discharge of the battery to another, when the battery is first fully charged and then discharged to zero. In practice, this method of operation is relatively rare - much more often the batteries are charged under-discharged, and sometimes the process has to be stopped before the charge is replenished to 100%. In addition, the number of charge cycles is usually indicated for ideal operating conditions: a “native” charger, a relatively low load during operation, compliance of the ambient temperature with operating parameters, etc. Therefore, the number of cycles indicated in the specifications is quite approximate, and in practice it is unlikely that you should expect a 100% exact match. Nevertheless, by this parameter it is quite possible to evaluate the durability of the battery and compare it with analogues.
Protection board
Built-in electronic circuit that protects the battery from operating conditions.
This function is found mainly in lithium-ion batteries (see “Technology”). This is due to the fact that such batteries have fairly strict charging and discharging rules; violation of these rules (primarily overcharging and overdischarging, as well as overcurrent) can lead not only to battery failure, but also to fire and even explosion. To avoid such troubles,
protection boards are used: they primarily control the charge level, as well as charging and discharging power.
This feature is highly recommended if the battery is to be used in a device that does not have its own battery controller. A striking example is electronic cigarettes with mechanical battery mods, in which the atomizer coil is connected to the battery virtually directly. Without a protection board, the customer must carefully control the operating mode himself - and this is not so easy, given the absence of any additional indicators in the same “mechanical mode”.
On the other hand, it is worth considering that this function affects not only the cost, but often also the dimensions of the battery - it can increase its length by several millimeters beyond the nominal size. For example, 18650 elements with a protection board are not 65 mm long, but about 68 mm. In some cases, this can create problems with installation, or even make it impossible. So if the device
...for which the battery is purchased has its own protection circuits, the optimal choice for such a load would be a regular, “unprotected” power source.USB charging
The ability to charge the battery directly
from a standard USB port, without using special chargers.
This feature significantly expands the battery charging options. USB ports suitable for this purpose can now be found in the vast majority of PCs and laptops, in 220V outlet adapters and car cigarette lighters, in portable power bank batteries, and devices with a similar function (such as powerful handheld flashlights). Additionally, some portable gadgets like smartphones and tablets can charge external devices using an adapter from a microUSB or USB C port. Another option is a built-in full-sized USB plug at the end of the battery itself; during operation, this plug is covered with a cap and the battery has a standard cylindrical shape, and for charging, the cap is flipped open.
