5 Things You Might Not Know About Powerbanks
Most people buy powerbanks based on indicated charging capacities. However, there are some details that we need to understand in order to maximize the use of these rechargeable batteries.
Powerbanks have become a huge secondary market commodity following the popularity of smartphones and tablets. It’s not a huge business that a lot of brands are coming out left and right.
In this quick guide, we explain why not all powerbanks are created equal.
1) Re-Charge Cycles and Lifespan. Powerbanks, like any other rechargeable batteries have a recommended recharge cycle. A good powerbank will have somewhere around 500 recharge cycles while sub-standard ones will have around 300 cycles only.
If you recharge your powerbank once a day, that means the lifespan can be somewhere between 300 days to 500 days. Once this re-charge cycle is fully consumed, the powerbank will no longer be able to re-charge to its usual capacity and degrades to about 50-70%.
2) Power Storage Capacity. Powerbanks cannot store 100% of the full power capacity that it states it can. Good ones can give you between 70 to 80%. Great ones like Anker powerbanks can go as much as 85-90%. That means if your typical powerbank says it can do 10,000mAh, the actual capacity could just be 7,000mAh.
This is called discharge efficiency and what is wasted or lost in the process is due to the internal circuitry of the powerbank as well as how good/efficient the batteries inside are.
3) Double A Batteries (cylindrical lithium-ion rechargeable). Most powerbanks use a 65mm AA-like re-chargeable batteries (18650, cylindrical lithium-ion rechargeable) connected in a series. These are easier to source, manufacture and assemble. That’s the reason why a lot of powerbanks have similar but odd-numbered capacities like 5,200mAh or 10,400mAh.
This is because they use multiple re-chargeable batteries (multiples of 2200mAh to 3400mAh) and not just one single large Li-Ion block. Some powerbanks which have thinner profiles do use a specific rectangular-shaped batteries like in smartphones.
4) Output Voltage and Output Current. The symbol mAh does not mean milliamps as most of us refer to but is actually milli ampere-hour and means measure of electric charge. One the other hand, Watt Hour (Wh) is a measure of electric energy.
The relationship of the two is shown in this formula:
milliamp-hour = watt-hour × 1000 / V
mAh = Wh × 1000 / V
The typical voltage for Li-Ion in powerbanks is 3.7V but output can go up to 5V. This is the reason why we see either of the two numbers in smartphones, laptops, or powerbanks.
The output current is measured in ampere which states how fast the current is passed thru the device. Most smartphones will use 1A while bigger tablets like the iPad might need 2.1A. Powerbanks have different ports for 1A and 2.1A while a fewer ones like Anker have intelligent sensing ports that auto adjusts the current depending on what the device needs.
Some phones like the Oppo Find 7 can handle up to 4A of current without damaging its internal battery.
5) Charging Cables. Charging cables are not created equal. Most cables have a data wire and a charging wire within the cable itself.
Typical charging cables are in the 28/28 gauge range with a wire diameter of about 0.321mm (first number represents the gauge of the data wire and the second number represents the charging wire). This is the reason why some cables could not charge phones or indicate slow charging.
We suggest getting a 28/24 gauge cable which are thicker. The 24 gauge ones are about 60% larger in diameter (0.511mm) and can handle 2amps of current. Of course, the cables can only transmit the same amount of power as the powerbank or power charger supplying it.
We also suggest to not attach the cable to the powerbank when it is not in use, especially in storage. It can still be feeding a small amount of current that can slowly discharge the powerbank.