What is a Power Bank and what can they charge?


Portable Power Banks are comprised of a special battery in a special case with a special circuit to control power flow. They allow you to store electrical energy and then later use it to charge up a mobile device. Power Banks have become very popular as the battery life of our smart phones, tablets and portable media players is outdone by the amount of time we spend using them each day. By keeping a battery backup close by, you can top-up your device(s) while far from a wall outlet.

The Power Banks we're talking about are good for almost any USB-charged devices. Cameras, GoPros, Portable speakers, GPS systems, MP3 players, smartphones and even some tablets can be charged from a Power Bank - practically anything that charges from USB at home can be charged from a Power Bank - you just have to remember to keep your Power Bank charged, too!

Power Banks may also be known as Power Stations or Battery Banks.

What types of Power Banks are there?

RED-E supplies two types of Power Bank found on the market today:

  • Our speciality is the Universal Power Bank. They come in many sizes and configurations that can be tailored to your device requirements and to your budget – they have built in cables for ease of use.
  • We also carry a Solar-Charged Power Bank. This has a photovoltaic panel, which cans trickle charge the internal battery when placed in sunlight. Solar charging isn't fast, so they can charge via cable as well.

How do I charge a Power Bank?

Most commonly, a Power Bank will have a dedicated input socket for receiving power. This power can come from a USB socket on your computer, but may charge faster when using a wall socket adapter available from RED-E. We most often see Power Banks use a Micro-USB socket for charging, and full-sized USB sockets for discharging. Always check the manual for specific instructions if you're not sure of the input socket.

Depending on the capacity of the Power Bank and its current charge level, it can take quite a while to fill up. For example, a 1500mAh rated Power Bank should take about the same time as your typical smartphone to charge. For larger banks, this time can be doubled, tripled or quadrupled. RED-E Power Banks have both an LED indicator to show when they are at capacity, and a safety cut-off to prevent overcharging and overheating. Whenever possible, remove the Power Bank from charge when it is full, or at least avoid leaving it connected long-term after its full. Ambient temperature and power flow will also affect charge times.

Some Power Banks don't work well with high-capacity chargers (like the ones that come with iPads), so rather use the standard wall chargers or smart phone chargers to charge your power banks.

How long does a Power Bank last?

This is a bit of an open question. There are two important life expectancies to consider:

  • The number of charge/discharge cycles a Power Bank can reliably perform in its lifetime.
  • How long a Power Bank can retain its charge when not in use.

The answer to point one can differ between models of Power Bank, their internal components and the quality of their manufacturing. We at RED-E do not to stock Power Banks which have fewer than 500 charge cycles in them. This would allow you to charge a device from the Power Bank every day for a 1.5 years before it started to lose its ability to hold charge long-term. Better and more expensive Power Banks can last longer, while smaller and cheaper units may fall short depending on their treatment. Power Banks are generally not used daily, so they often last much longer than 18 months in real-world usage patterns.

Point two depends on the quality of the controller circuitry and battery cells. RED-E Power Banks can hold charge for 3 to 6 months with minimal loss. Lower quality Power Banks may struggle to retain a useful charge more than 4 to 6 weeks. In this regard, you get what you pay for, and if you need a long-term emergency power supply consider increasing your budget to ensure you're not going to be caught short. Most Power Banks will slowly lose charge over time, to a degree influenced by the environment and their treatment.

How many times can a Power Bank charge my device?

RED-E Power Banks boast efficiency ratings up to and over 90%, but we find that real-world usage in South African climates typically ends up with a 75% efficiency rate. We also like to be on the side of caution to give you a conservative estimate rather than make outrageous claims. Generally, the bigger the Power Bank and the smaller the device you're charging, the more goes you get. Other factors can also improve or limit the discharge potential of a Power Bank, so look after them and they'll work better for longer.

Our Formula:
Power Bank Rating (mAh) × Efficiency × Device Depletion ÷ Device Capacity (mAh)

6000 × 0.75 × 0.75 ÷ 1500 = 2.25 charges (approximately)

Technical Term Glossary

What does mAh mean?

Batteries common to mobile devices and Power Banks are rated on their ampere-hours, measured in milliamps to create non-decimal numbers. The mAh ratings denote capacity for power flow over time.

Li-Ion & Li-Polymer

Lithium-Ion and Lithium-Polymer batteries are the most common rechargeable cell types found in Power Banks. Lithium-Ion cells are generally cheaper and limited in mAh capacity, while Lithium-Polymer cells can be larger and don't suffer from a memory effect over time.


When power is transferred; there is always loss due to resistance. Power Banks are not able to transfer 100% of their actual capacity to a device, so we factor in this loss when calculating how many times an average device can be charged from a fully powered Power Bank of any given size. Efficiency ratings differ between Power Banks based on their cell type, component quality and environment. Ratings between 75% and 80% are the current industry standard. Beware of suspiciously low-cost options claiming efficiency ratings of over 90%.

Device Depletion

This is the state of the battery in the device you wish to charge. The lower its power, the more a Power Bank has to work to bring it back to life. We consider charging from 20% to 90% a full charge, as the efficiency loss increases beyond these points, leading to wasted charging potential. Going from 5% to 100% can take exponentially more power.

Choosing the right Power Bank

If you have a specific need in mind for a Power Bank, we probably have the perfect product for you! Use our formula above to get a rough estimate of the number of charges a topped-up Power Bank will give you before it needs to be recharged itself, then compare your needs and budget to our range.

When you need something truly mobile, our 15000 mAh Power Bank offers good capacity in a very small form factor. Slimmer still is our 8000 mAh design. Both of these can easily go in a pocket, purse or bag.

If you're looking for an entry-level Power Bank on a budget, our 4000 mAh or 6000mAh is a great start.
For an even cheaper 'one-shot' charger, our 2500mAh model can easily top up your smartphone in a pinch.

Going camping? Why not consider our solar-charged 7000 mAh Power Bank?
It only has enough juice for a good few charges, but can charge itself in sunlight.

Too much Power?

If you're spoiled for choice and need to know more about our Power Banks, just contact us! We'll put the power in your hands - no worries!


Contact Details


Telephone: +27 (21) 691 0110
(During office hours)


18 Induland Crescent
Cape Town
7780, South Africa