Power Banks - Is the juice worth the squeeze?
8th December 2022
Battery anxiety is a thing!
How many times have you been caught with zero power? Typically, our devices always die at the most critical of moments. Our lives are dependent on mobile technologies; they have changed the way we work and play beyond all recognition. Whilst battery life has improved over the years, our use of devices has also skyrocketed. Dare anyone check the time spent daily on their smartphone? Despite power-efficient developments most of us find ourselves charging items almost daily to help us stay connected.
We charge at home, at work and in our cars – praying that the dreaded low battery symbol doesn’t pop up. Having spent a fortune on low quality charging devices for every scenario we may find ourselves in and, subsequently, every single one of them breaking or not giving us 100% power, there has got to be a better solution.
Enter, the power bank, sometimes known as a charging bank. These compact bricks of seemingly endless power have the capacity to keep our batteries topped up for days. However, with so many variables across capacity, charging speed, and connectivity it can be hard to decide which power bank is best for your needs.
A power bank is a portable battery designed to recharge electronic gadgets when you don’t have access to a regular wall charger. Ranging in size from slim, pocket-sized devices up to larger, high-capacity power banks – they can be used to charge cell phones, tablets, cameras, portable speakers, gaming consoles, or even laptops.
How does a Power Bank work?
Since power banks are basically regular batteries with some extra features, they work just like any other battery that is rechargeable. They store energy up to their maximum capacity and then release it when connected to a compatible device that needs recharging. It is as simple as that.
What type of Batteries do Power Banks use?
Power banks generally come with either Lithium-Polymer (Li-Po) and Lithium-Ion (Li-Ion) batteries. Of the two Li-Ion power banks are more popular.
In terms of differences between these two types:
Lithium-Polymer batteries have a higher energy density, but they tend to have a shorter lifespan and are also more expensive to manufacture. They’re also less prone to explosion.
Lithium-Ion batteries, on the other hand, have a slightly lower energy density but they can withstand more charge/discharge cycles and are generally less expensive.
Charging a Power Bank
The most efficient way to charge a power bank is to use a wall charger that can deliver a high power output. Using a low-quality wall charger that only delivers 2A for example, can extend the recharging time for several hours. Another way to charge a power bank is by using a charging station. Other ways to charge a power bank are using your laptop USB port, a car cigarette lighter, or using a solar charger like in the case of the BigBlue 28W or the Anker 21W. However, all these methods are slower and you should avoid them unless you can’t access a wall charger.
It’s important to avoid overcharging your power bank. This can be damaging to the battery in the long run. This is why after plugging it in, you should check the charge indicators from time to time. Some power banks, however, do come with overcharging protection so you don’t need to worry about it. Check your user manual to see if your portable charger has this feature or not.
In all the scenarios, it is recommended that you follow the manufacturer instructions associated to the power banks. In some cases, they may recommend that the power bank be fully discharged from its factory condition and then be recharged. In some cases, the power bank can be recharged right from its box. The same goes with the wall adapters in case you choose to use one that did not come with the product.
Power Bank Capacity
All power banks are different even though, on the surface, many look similar. As mentioned in the point above, most power bank units will fall into one of two categories focused on lithium technology. All power banks use rechargeable batteries, but one may use lithium-ion whereas another may use lithium-polymer. The most significant difference between the two types is the chemical electrolyte between their positive and negative electrodes. This boils down to lithium-ion holding a higher power density and a lower cost compared to lithium-polymer. However, lithium-polymer batteries are more robust, flexible, and have a lower chance of suffering with leaking electrolyte. Both forms of battery work effectively and have their pros and cons. However, it will largely depend on the design and manufacturing of a power bank as to whether it delivers the charge you need.
All power banks have a listed capacity which is the value that the manufacturer claims for the design of that battery, whereas the real capacity is a property of that battery at a given moment in time and conditions. The real/actual capacity of a battery varies from rated capacity because of manufacturing tolerances. It decreases with consumption, and also depends upon temperature and discharge rate.
How long does a Power Bank last?
This one is a tricky 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 number of charging/discharging cycles can differ between models of power banks, their internal components and the quality of their manufacturing. The most commonly recommended threshold is for 500 cycles at least. This would allow you to charge a device from the Power bank every day for 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. A good Power bank 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. For example, leaving a Power bank in the car where the temperature can fluctuate greatly over time can shorten its lifespan.
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.
Efficiency
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 80% and 90% 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.
Do I Need a Power Bank?
Short answer is most definitely a yes.
Having a power bank only ensures that your device will not run out of juice too fast. However, as demanding as we humans are, not all devices are capable of getting charged as quickly as we need them to. Some devices do support a fast charge feature. In such cases, a power bank with a higher output can be godsend. If the device does not support fast charge, it does not matter how awesome the power bank is with regards to its output, it will still take its own sweet time. Your device can only withdraw as much energy from a power bank as the charging circuit within it is designed for. If you have a smartphone with a circuit built for 5V/1A, it will not handle the wattage of 5V/2A and won’t charge any quicker than usual. You will be able to check the fast-charging standard of your device by looking at the specifications or user manual.
The same applies while charging power banks themselves. Some power banks don't work well with high-capacity chargers (like the ones that come with iPads) unless it is designed for the same. Trying to fast-charge a power bank from a 2A charger can result in damage to the internal circuitry, which isn't covered by warranty.
So do find an optimal balance between cost and purpose that you intend to use it for. Remember, more expensive not necessarily equal to a better power bank.
Do let us know your thoughts and questions on this topic in the comments section below.