Truth about Portable Battery Power bank

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smartphones have become our daily life

companion and we need more and more

battery life mostly a full charge is not

enough for a day if you have the user

the easiest way to expand your battery

life is a power bank but which one

should you buy if you check out power

banks on Amazon then you can find a lot

of mixed reviews many reviews are paid I

know that from my experience and some

reviews are just from people who have no

idea what they're talking about so most

people just search for the biggest

capacity advertised for a low price but

this is something you should not do and

the reason is that sellers mostly lie

about the capacity the first let me

explain how a power bank works and why

you can't simply divide your power banks

capacity by a sound battery capacity and

get the charging cycles so there are

different kind of power banks with

different battery technologies on the

inside cheaper power banks use

lithium-ion cells especially the

affordable 18 650 cells they are cheaper

and they have six sizes but well that's

the only advantage they have a higher

discharge rate just to get hotter and

are not really durable compared to the

new lithium polymer cells

however Lipa power banks more expensive

and also harder to get but they are

smaller and more durable on the long run

also the Liam ion batteries can catch

fire more easily because of their fluid

electrolyte Lipa batteries instead they

use a solid or gel electrolyte and a

more safe well I know it's not very

realistic that the power bank will catch

fire but safe safe and here's a quick

video I recorded two years ago and

imagine your power bank gets shorted and

blows up like a note 7 and that's not

really funny now let's talk about the

actual capacity because he it gets

tricky power banks get to 99% produced

in China and most cheap unknown

manufacturers of OM data sly about the

battery capacity you can't imagine how

many emails I get every day of power

bank sellers and they want to sell me

the latest product but I just see the

first looked at so that's a fact

but although the capacity advertised is


the actual capacity that goes into your

sounds battery

so first the capacity inside is measured

as mah that stands for milliamp hours

and tells you how many milliamps or amps

you can drain from the battery in one

hour so for instance a 10,000 milliamp

hour battery means you could drain

10,000 milliamp to 10 hours for one hour

or for instance um 1,000 milliamps for

ten hours but you can only do this at

the rated voltage of the cells and most

cells are rated at 3.7 volts if you

multiply a million dollars and the rated

voltage you get the actual energy which

would be three point seven watt hours

that means you can drain three point

seven watts for one hour from the

battery but why do we need to know all

that so you need to know that USB ports

are made to operate at five volts so you

always plug it smartphone into five volt

source this is the output of the normal

USB port of your notebook or phone

charger so inside of the power bank the

voltage has to be stepped up from the

three point seven volts to five volts

using a boost converter this conversion

is not lossless that means there is a

conversion loss to calculate the root

capacity take the advertised power bank

capacity times three point seven and

divided by fire this is now your real

capacity and it's always lower than the

advertised one the second factor is the

efficiency factor and this one depends

on your power bank cheaper banks have a

bad convert inside that transforms a lot

of energy into heat which is lost high

quality power banks have better up

stepper resulting in a small loss so

good power banks lose here let's say 50%

some you in 20 or way more now let's do

the math your 10,000 mah power bank at

frequent cell walls actually can only

supply seven thousand four hundred

million dollars at five volts and if the

converters crap then maybe even less and

maybe in a couple of months even more

less because it sounds alter so if you

thought that you could charge your 2000

mAh not found five times with

10,000 NH battery then you know

disappointed because it just has 5900 MH

coming from with power banks use B port

and there is another conversion in your

smartphone back to 3.7 volts so this

advertised 10,000 mah power bank will

charge a smartphone only around 2.5


What you should know before buying power banks ?

Smartphones became part of our life

We use to talk, play games,

listen music, watch videos & lot more

Eventually, all these drains the smartphone battery

Therefore, to charge we use portable power bank

so that it can charge our mobile

for N number of times

depending upon the power bank capacity

After buying the power bank,

one can probably get these questions

How many times that this

power bank can charge my mobile?

Does this power bank contain same

capacity as advertised in the label?

This video will answer all your questions

and also the marketing strategies

behind the power bank

Here, we gonna we about the power bank specifications

Consider that I am using a power bank

of capacity 15,600mAh

Let's remove the front plastic case

to see what is inside the power bank

Normally, it contains two major parts

The circuit named battery charging board

and the parallel connection of battery cells

These cells are Lithium-ion 18650 cells of 3.7volt

with capacity ranging from 2,000 to 3,000 mAh

In my case, it is 2,600 mAh

While in parallel connection of these six cells,

the total capacity is the sum of each cell

Thus, the rated or advertised capacity

of this power bank is 15,600 mAh

with same voltage of 3.7V

But for USB charging, the smartphone needs the

power with voltage of 5V

So, this board in power bank

converts 3.7V to 5V for smartphone

This process is known as Boost converter

Therefore, the rated power bank capacity get reduced

due to this voltage conversion

To find the USB output capacity,

we need to multiply the rated or

advertised capacity with 3.7V

and then divide it with 5V

For this power bank of 15,600 mAh capacity

is equal to 15,600 * 3.7 divided by 5

is equal to 11,544

Thus, the USB output capacity is equal to 11,544 mAh

Also, we have to consider the losses like

Conversion loss, losses in USB cable

and losses in phone charging circuit

which produces heat

This reduces the power bank efficiency

For a good or new power bank, 

the efficeincy is 90%

For average or old power bank,

the efficiency is between 70% and 90%

So, the actual capacity of the

power bank is obtained by

multiplying the USB output capacity with

efficiency of 90% or by factor 0.9

11,544 * 90 divided by 100

is equal to 10,390 mAh

This gives the actual capacity for charging smartphones

For finding N number of

full charges for smartphones

N is equal to actual power bank capacity

divided by mobile battery capacity

Considering 3,000 mAh as 

average mobile battery capacity

So, N is equal to 10,390 divided by 3000

is equal to 3.46 times

Here, 3.46 is the number of times

that power bank can charge 3000 mAh battery

Finally, the marketing strategies behind the power bank

When you notice the specifications

label in the power bank

You can only see the rated capacity in mAh for 3.7V

rather than actual capacity for 5V

Power bank manufacturers advertise

the rated capacity in 3.7V

which is larger and can attract more customers

It is genuine in their own way

So, it's us customers who need

to calculate the actual capacity

There is also an exception

This chinese power bank mentions

rated capacity in 3.7V

with actual capacity in 5V

and also claims its efficiency

has greater than 90%

This case is rare, really very rare!

To calculate for your power bank and smartphones,

Use these formula

Replace advertised capacity

with your power bank capacity

Then, find USB output capacity and actual capacity

Also, replace the battery capacity

with your mobile battery capacity

Then, find number of full charges

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