Choosing a power bank: what mAh really means

This is general buying advice. It does not describe any particular product: check each product page for what is actually listed.

A power bank is a battery in a box. Choosing a good one comes down to three questions: how much it stores, how fast it can charge, and what you want to charge with it.

What mAh means

mAh stands for milliamp-hours. It is a measure of how much charge the battery holds, so a bigger number means a bigger battery. A 20000 mAh power bank holds roughly twice as much as a 10000 mAh one.

The catch is that the figure on the box is measured at the voltage of the cells inside, about 3.7 volts. Your phone charges at 5 volts or higher, so some of the stored energy is lost converting it. As a rule of thumb you will get somewhere around 60 to 70 percent of the labelled capacity into your device. A 10000 mAh power bank will not give a phone with a 5000 mAh battery two full charges. It gives closer to one and a half.

ZS - Type-C PD22.5W Mobile Power Bank 10000mAh Fast Charging — R199.99

Work out the size you need

Look up your phone's battery size in its specifications, then multiply by how many full charges you want and divide by about 0.65 to allow for the losses.

One extra phone charge a day: a 10000 mAh power bank is usually enough.
A weekend away, or two people sharing: 20000 mAh and up.
A tablet or a small laptop: look at the watt-hour rating if there is one, because laptops need far more than a phone does.

Output matters as much as capacity

Capacity is how much, output is how fast. Look for the output in watts, and for the connectors on the box. A basic 5 watt output will take hours to fill a phone. Phones, tablets and laptops that support fast charging need a power bank that supports the same standard, and the cable has to cope with it too. A cheap thin cable can slow everything down.

Two or more ports are handy, but remember that when several ports are in use the output is shared between them.

ZS - 30000mAh 22.5W Fast Charging Power Bank with Built-In Cables — R499.99

Other things to check

Input speed. A large power bank that charges at a slow rate can take a whole day to refill. Check how it charges itself.
Size and weight. Bigger batteries are heavier. If it lives in your handbag every day, a very large one gets tiring.
Pass-through charging. Some models can charge a phone while they are themselves charging. Not all do.
Flying. Airlines generally limit the size of power banks you may carry in the cabin and do not allow them in checked luggage. Check your airline's rules before you travel.
Care. Keep it out of a hot car. Stop using any power bank that swells, gets very hot, or has been dropped hard.

Load-shedding use

During load-shedding a power bank keeps phones, a router's backup or a small light going. Remember that a router needs a specific voltage, and a power bank that is not designed for it may not work. Check the voltage the router needs before you buy.

ZS - 50,000mAh Fast Charging Power Bank — R499.99

Some options from our range

The list below is taken live from products in our shop that are in stock right now, with the price as listed. Open any product to read its own description and details.