Understanding Power Banks: Why don’t they give the charge as mentioned?

Power Banks have become one of the very necessary smartphone accessories these days, haven’t they? true for the reason that the smartphones although come with heavy power to handle all the functions, the battery tends to last for no more than a few hours. That is where these power banks come to use, giving the charge needed when there is no direct power source available for your phone charger. There are power banks from even 2000 mAh to over 20000 mAh capacity, and there has been a general perception in the minds of users that the number mentioned for the power bank is the total charge that it is able to provide. For example, if it is a 10000 mAh power bank, the user expects to charge his 2000 mAh phone for five times. That isn’t really the case though.

If you are buying a mobile power bank with the calculation that it might give with the calculation given above, you are mistaken. There are a few factors that contribute to the capacity:charge percentage. And there are a few different equations used to calculate the same. One of the most common formula used:

Total charge times for a particular phone = Power Bank Real Capacity * Conversion Rate * Phone Battery Health / Phone Battery Capacity

For example, for a phone with 2000 mAh capacity and 0.8 battery health, a power bank with 10000 mAh capacity and 0.8 conversion can give a charge for about 3.2 times (10000 x 0.8 x 0.8 / 2000), and this could be even 3 times to 4 times, as it is not easy to understand the conversion and battery health.

[quote align=’right’] The battery in your phone is strongest when it is new. With age and with charge cycles, the health of the battery keeps getting lesser. [/quote]Conversion: There are certain functions that happen in the power bank when it sends the current to the phone battery. The PCB operation is the main function, and during this, some battery is lost due to the heat produced (although practically cannot explain, that is what the books tell).

PCB is Printed Circuit Board, and it is the one that controls all the operations that happen inside the power bank. It also depends on the quality of PCB, on how much durable it is and how much charge the power bank can provide on full capacity.

Phone Battery Health: The battery in your phone is strongest when it is new. With age and with charge cycles, the health of the battery keeps getting lesser. There are apps that test your battery health, and although they cannot be called 100% accurate, still would give an approximate estimate about the current health of the phone battery.

And again, before you come to a conclusion about the approximate charge, it is very important to know about the type of power bank you own, or are going to purchase. There are two very common types of power banks available globally, although most of them are made in China – Li-ion 18650 power bank, and Li-Polymer power bank.

Most of the cheap power banks available in the market are made with the Li-ion type 18650, because they are cheaper and their sizes are fixed. While being cheap is the only advantage here, the 18650 Li-ion power banks have a higher discharge rate, loss of durability is faster and they produce more heat when compared to the Li-polymer power banks. But for the Li-polymer power banks are not very easily available, except through the well known accessory makers, and they are quite expensive.

Another difference is that the Li-ion 18650 power banks have batteries that use liquid electrolyte, while the one in Li-polymer uses solid or gel electrolyte. It is safe to use Li-polymer batteries, because according to experts, if there is a defect in manufacturing the Li-ion based power bank, overcharging can lead to leakages or sometimes, it can even lead to blast of power bank.

What about the charge cycles and power bank health?

This is similar to the smartphone batteries, whose health is not constant. A charge cycle is counted as a charge from 0-100 and back to zero, and such 500 charge cycles in a power bank can result in about 20% loss in health. So, if you are using a 5000 mAh power bank and use it regularly, 500 charge cycles will bring down its capacity to about 4000 mAh. This is very normal, as you are regularly using it and the reduction in capacity is bound to happen.

What to select? 5V/1A or 5V/2.1A

There are certain parameters for the charge output from the power bank, like 5V with 1A and 5V with 2.1A, and rather than you selecting what to choose, it should depend on the device you are charging. Many users end up buying and using the 5V 2.1A combination, but that is applicable only if the phone you are charging, can take up that speed. If your phone has an input of 5V/1A and you are trying to use the USB port with 2.1A output in your power bank, it won’t speed up the charging at all. It is better to use 5V/1A if the input is the same, and only if you have a powerful device with battery that can take the 2.1A speed, you can use that for faster charging.

A few things to know about Power Banks

• A power bank whenever fully discharged, has to be charged back soon or there is reduction in the battery lifespan.
• Sometimes, it takes just a few hours to charge a heavy capacity power bank and sometimes even half a day. The difference is because of a lot of things such as temperature, rate of power flow from the power socket, battery health, etc.
• If you are using a power bank rarely and still have it for specific purposes like travel, it is safe to charge it fully and discharge it at least once a month to keep the battery active.
• The calculations done for the number of times a phone can be charged, is again dependent of factors such as phone usage, temperature in the surroundings, etc. For example, if you are charging your phone with the power bank, and at the same time, are using the phone with Internet or watching movies, the calculation can go wrong. Because, the battery is significantly dropping in your phone and the power bank is coping up with that too.

Another formula used by a few power bank manufacturers, to come out with an approximate capacity of charge provided to the smartphones, is:

Rated Capacity = Power Bank Battery Capacity x Battery Voltage 3.7V / voltage boost 5V x Conversion Efficiency

Though, it is better to use the formula we mentioned above, as the approximate value given there is near accurate and you at least get an idea of how many times your phone can be charged before a fully charged power bank gets discharged. Thus, whatever is mentioned on the box of your power bank is for the battery of the power bank, and it is not the actual capacity to which the mobile phone batteries can be charged. There is a difference, and you have to keep that in mind while selecting and purchasing a power bank for your mobile.