How to choose an external battery

We will tell you how to choose the capacity, power and which chips to pay attention to. The checklist is at the end.

Which container should you choose? Difficult mathematics

Imagine you have a smartphone with a 5000 mAh battery. How much capacity does a powerbank need to charge your battery twice? It would seem 10,000 mAh. But no.

The vast majority of external batteries use lithium-ion batteries 18650 with an output voltage of 3.7 V. And the standard voltage with which power banks charge your devices is 5 V. And most often manufacturers indicate the battery capacity for 3.7 V, and to get value for 5V, you need to multiply the capacitance by 0.74. That is, at a voltage of 5 V, a real 10,000 mAh can be given by a model that has (conditionally) 13,500 mAh in characteristics.

In addition, one should not forget about efficiency and self-discharge. All 100% of the power bank’s capacity will not go into your smartphone, since some of the transmitted energy is converted into heat. And if the battery is left in the bag for a week, it will lose some of its charge during inactivity.

So the stock should be set at least with a factor of 1.5. Want to fully charge your 5000mAh battery 2 times? Take a 15,000 mAh power bank.

There is a nuance: an average 10,000 mAh power bank weighs about 200–250 g. 20,000 mAh is already almost half a kilo. For fishing and travel it is quite normal, but for every day it is better to find an easier option.

Input Connector: Which Is Better?

The input connector is labeled in the specifications with the abbreviation IN and is needed to charge the battery itself. To reduce the amount of wires used, choose a model with an input connector like your smartphone. For example, if you have an iPhone, you can take a mobile battery with Lightning.

If a smartphone with microUSB, think about whether you will be changing it in the next couple of years? Not going to change – feel free to take with microUSB

But most modern models are already with USB-C, so a powerbank should be taken with the same connector. However, some models charge from both USB versions. For example, Redmi PB200LZM.

Another important point is the charging speed of the powerbank itself. The power that the input connector supports speaks about it: the more it is, the faster the battery will charge. True, most often manufacturers indicate only the current strength (for example, 3 A). Although this figure does not give a complete idea of  the charging speed, it can still be guided by. The rule is the same: more is better.

Power and fast charging

The charging speed of devices depends on the power supplied by the mobile battery. The higher it is, the faster the energy supply will be replenished. You can find out the output power in the characteristics of the device. And if not, look at the amperage and voltage, for example 3 A / 5 V or 2.5 A / 9 V. To get the power, simply multiply one by the other.

It is important to clarify that any device will be charged with a voltage of 5 V. And for fast charging to work, both the smartphone and the powerbank must support the same fast charging standard: Power Delivery, Quick Charge, MediaTek Pump Express, Huawei SuperCharge, Samsung Adaptive Fast Charging and others.

In power banks that support charging multiple devices at once, power is often distributed equally to all connected gadgets. That is, if the description indicates 18 W, only one smartphone will receive all the power. And if you charge two at once, the power will be divided by 9 W for each gadget.

From bricks to toys

The same container is hidden in different cases. For example, a power bank can be long but thin or short but thick. If you plan to carry it in a small purse or pocket, the slim body will be more comfortable. And there are just funny models, for example, Hiper Zoo Mint Pie in the form of a kitten.

Wireless charging: a great bonus

If your smartphone, watch or headphones support wireless charging, take a look at external batteries with this function. This way you don’t have to carry wires with you. An example of such a model is the Xiaomi Mi Wireless Power Bank Essential.

A good power rating for models with wireless charging is 10W and above. With a power of 5 W, the watch and headphones will more or less charge, but the smartphone is unlikely.

Wireless charging speed is sometimes limited by the device itself. For example, the iPhone 12 with conventional chargers supports no more than 7.5 W, and reaches the maximum 15 W only with a proprietary MagSafe charger.

Is it possible to charge a laptop?

Thanks to the USB-C port and the Power Deliver protocol, modern power banks deliver up to 100 watts of power. For comparison: 16-inch MacBook Pro

Featuring a powerful processor and discrete graphics, it charges with a 96W power adapter. You won’t notice the difference between an outlet and a power bank.

But there are two nuances:

  • Your laptop and powerbank must support the Power Delivery protocol. USB-C does not guarantee it.
  • The power output of the USB-C port of the external battery must be at least equal to the power of your laptop charger.
  • If you don’t want to guess with the power, the option with the maximum Power Delivery of 100 watts is suitable for most laptops. For example, Hiper ForcePower 100W

So, a simple checklist:

  • Choose a container with a margin of 1.5 times.
  • For every day it is better to take a model with 5,000-10,000 mAh, it will be difficult to carry more capacious ones.
  • Look at the power, and if it is not indicated, at the amperage and voltage.
  • If the powerbank and your devices charge through the same connector, you don’t have to carry an extra cable with you.
  • You don’t need wireless or fast charging if your smartphone doesn’t support them.
  • To charge the laptop, both the powerbank and the laptop must support Power Delivery, and the power output of the external battery must not be lower than the main charging power.