Gennady Yagupov: How to Choose a Portable Battery

Every cell phone manufacturer is trying to solve the impossible task of giving their device maximum memory and performance, equip it with all possible options, but at the same time make it as light and thin as possible.

Unfortunately, they often try to solve this problem at the expense of battery capacity. Many modern smartphones hold a charge for literally 24 hours, even when just “out of the box” site yagupov.

And sooner or later there comes a moment when you need to make an important call, or you are waiting for an important call, or you need to urgently get important information from the Internet, or… and the phone shows 0% charge and turns off. It’s good if you have a charger handy and there’s an outlet nearby, but what if you don’t?

The lifebelt in this situation will be a power bank.

The disadvantage of portable batteries is that it brings additional complexity to our already busy life with the care of various gadgets: it must be recharged in time, do not forget to put it in a bag or backpack; in the pocket it is uncomfortable to carry it – heavy, etc.

There are smartphones on the market with a high-capacity battery that can hold a charge for days or even weeks.

But, first, for many models of smartphones there are simply no analogues with large batteries.

Secondly, “long-life” smartphones are heavy and bulky.

Third, the presence of a high-capacity battery does not guarantee that you will not one day find yourself “in the clear” with a discharged phone in his hands. Even on the contrary – the long life on a single charge in such models gives a false sense of “eternal” charge, and they switch off somehow quite unexpectedly.

The portable battery has some advantages over the built-in battery, in addition to the fact that it maintains the light weight of the smartphone:

  • It can charge not only smartphones, but also other mobile devices powered by USB
  • Some models have additional features: flashlight, solar panel, card reader, etc., which greatly expands the scope of their application.

Portable Battery Specifications


The capacity of a portable battery is its main parameter, which primarily determines its attractiveness and price. The greater the capacity of the battery, the more times it will be able to fully charge your smartphone or other gadget.

But before you buy a battery with several tens of thousands of mAh, you should assess whether such a capacity will really be in demand.

If you need a battery only to be able to use a suddenly “dead” phone in a critical situation, then the battery of minimum capacity will be enough – it will be lighter, and easier to handle, and much cheaper.

If you plan to use the battery while traveling, it is better to take a battery with enough capacity for several full charges of your smartphone.

And if the battery is planned to charge not only a smartphone, but also other gadgets – up to a laptop, then there is no need for any extra capacity.

When selecting the capacity you should not lose sight of an important point: not all of the capacity of the portable battery is able to “transfer” to the battery of the gadget being charged.

The number given on the case of the portable battery – this is the nominal value. This capacity will be given by its cells when they are discharged with the rated current. But in actual use, the discharge currents are much higher, plus it is often the case that the discharge voltage is higher than the rating of the battery cells – and some energy is also lost in the conversion.

Plus, it should not be forgotten that lithium-ion batteries (of which most portable batteries are composed) “do not like” full discharges – part of the charge must be left in the battery, otherwise it will quickly fail.

With all these features in mind, the working capacity of the battery – the one that it can transfer to the charging devices – is 60-70% of the rated capacity. And the higher the current and voltage is charged, the lower this percentage is.

Output Voltage

The output voltage should be chosen according to the characteristics of the device being charged.

An output voltage of 3.7 (3.8) V can be used to charge most battery cells which are rated at exactly 3.7 V. And with this voltage the cells can be charged directly, without a charging controller.

The advantage of batteries with an output voltage of 3.7 volts is that their efficiency is slightly higher due to the lack of output voltage conversion.

And the disadvantage is that their versatility is limited – the standard supply voltage at the USB connector (which most such batteries are equipped with) is 5 V, and if you try to charge it with a device whose charging controller requires exactly 5 V, the device will simply refuse to charge.

The 5 V output voltage is the power standard of the USB connector through which most mobile devices are charged today. Not surprisingly, this output voltage is the most common on portable batteries and the most versatile. Any device with USB charging simply has to be powered by the 5V jack.

Output voltages of 9, 12, 16, 19 and 20 volts on a separate connector are designed to charge more “oversized” mobile devices, most commonly laptops and tablets.

Usually the voltage value on the connector is set by a button on the external battery, and the connection to the device to be charged is made with the appropriate adapter.

Before charging devices with such a battery, you should carefully make sure that the voltage is set correctly and the adapter is installed properly – otherwise it is possible to damage the charging device. It is not superfluous for such a model to have a display that shows the charging voltage.

It also happens that output voltages greater than 5V are given in the specifications of the battery, which has only USB output connectors. The USB 3.1 standard allows a supply voltage up to 20V – but this is only set automatically and only after the charger has “told” the charger that it is ready to accept the higher voltage.

If the USB voltage can be set manually on the battery, it is better to refuse from such a battery – the risk of “burning” the charger is too high.

Current strength (output)

The current strength determines the suitability of the battery to charge tablets and laptops (many of them require charging currents of 2 to 4 A) and also indicates how fast the battery can charge the phone.

A battery with a maximum output current of 0.5A will take twice as long to charge your smartphone as a battery with 1A. If the smartphone is able to charge with a current of 2A, then the charging time (from the corresponding battery) will be reduced by half.

At the same time you should not be afraid of “burning” the smartphone with an increased charging current – all modern phone controllers limit the charging current to the optimal value.

The advantage of the battery with a low output current is one – such a mode of discharge is more favorable for the battery and its operating capacity will be higher than that of a portable battery with a similar nominal capacity, but a high output current.

Support for fast charging. Many modern gadgets are able to speed up charging time by 40-50% by taking advantage of USB 3.1’s ability to change the supply voltage and current.

When in fast charging mode, the controller monitors the battery being charged and adjusts the voltage and current to deliver the proper amount of charge. Different manufacturers use different standards for fast charging and if this feature is important to you, make sure before you buy a battery that it supports the same fast charging mode as your smartphone.


Most portable batteries are universal and can be used to charge any gadget with an appropriate connector. But if you want to be sure that the battery has the right connector and supports all charging modes of your gadget, choose among the compatible models.

Battery type

Lithium-ion (li-ion) batteries are made from typical cells (looking like thumbtacks), they are relatively inexpensive, but prone to self-discharge and are very warm at high currents.

Lithium polymer batteries have a higher capacity and are safer, but also more expensive.

Output connectors

The output connectors on the case are used for charging devices, it is advisable to choose a battery with the connectors that you may need.

Most devices, if not directly charged by USB, have an adapter for it, so the USB output connector is the most common. Often there is also a miniature version of this connector – microUSB.

Recently, more and more widespread is the connector USB Type-C – many devices with support for fast charging have this connector charger.

And let’s not forget about Apple devices which traditionally avoid common standards: If you own an iPhone or iPad, you will need a portable battery with a proper output jack – apple 30-pin or apple Lightning – to charge it.

The input jacks on the case are used to charge the battery itself. Some batteries have their own power supply with a separate connector, most charge from the same USB/microUSB.

Owners of Apple equipment may be more convenient battery that uses the Lightning connector for charging – such a battery can be charged by the regular charger Apple.

The number of USB ports greater than 1 may be useful if you plan to charge multiple devices at the same time.

But keep in mind that the battery probably will not be able to hold the maximum output current on all connectors. The output current of the battery is “divided” by the connectors used: if you connect two devices to a battery with a maximum output current of 2A at the same time, each device will only get 1A.

Choice of portable battery packs

If you need an inexpensive and compact device that can help you use your phone when it suddenly runs out of power, choose from low-capacity budget models – it may not fully charge your smartphone, but it won’t leave you without a connection at a critical moment.

If your smartphone is fast-charging, and you want your portable battery to charge faster too, choose models that support fast charging.

To be able to fully charge the battery smartphone 1-2 times – choose models with a capacity of 10000 mAh. To determine how many times the battery can charge your phone, increase the phone battery capacity by 35% and divide the capacity of the portable battery by the resulting number.

Traveling away from civilization requires a high-capacity battery.

To be able to charge not only your smartphone but also your tablet or laptop, choose among models with higher capacity and high voltage charging capability. Note that the list of charging voltages should include the required voltage for your laptop or tablet.

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