How to check power bank's capacity?

How to know if the power bank is real capacity as its marked?

Power bank becomes necessary for Smart phone users. As end users, how do we identify its performance of good or bad?

First of all, we need to learn knowledge capacity. Power Bank’s marked capacity is based on internal batteries of nominal capacity and the actual output is less than the nominal capacity. We take a case to explain and analysis the capacity.

A friend, he bought a 6000mah Power bank, so-called conversion rate can reach 90%, but why it’s not able to charge 3 times of Ipones4s? 

As we know, Iphone 4S’capacity is 1460mAh and according to the most simple arithmetic, 6000÷1460≈4.11.That is to say, 6000mah battery should be able to charge full of 4 times but why is a far away from actual situation? Let's talk about Power Bank conversion efficiency and first we briefly explain the charging principle of Power Bank. The current Power Bank using 18650 Li-ion batteries or polymer batteries, the nominal voltage is 3.7 V, and digital products such as mobile phone standard input voltage is 5V.Therefore, it needs to boost to 5V when charging these mobile devices.

Real capacity after boosted voltage

According to energy conservation law: the 6000mAh Power Bank’s capacity is 6000mAH×3.7V=22.2Wh. After transforming input voltage from 3.7V to 5V, the total energy is constant, but the capacity has changed into 22Wh÷5V=4400mAH. It likes put 3.7L water into 5L glass. After first conversion, the 6000mAh capacity remain 74%, namely, the 4400mAh is the reality capacity can provide to mobile phone.

Energy loss in charging

In the next step, we using the data cable connect Power Bank and mobile phone to charging. The question is, can be the 4400mAh capacity fully reach the battery in mobile phone? Answer is NO. In the processing of charging, there are many energy losing:
　　
1. Circuit switching loss. As we all know, Power Bank generates heat when it is charging. According to energy conservation law, the heat is from the energy of internal battery.

2. Resistance loss. Power Bank’s battery is linked with mobile phone’s battery through circuit board and wire when charging. As we know, all conductors (except superconductor) exit resistance. The main physical characteristics of resistance are changing electric energy into heat energy. Therefore, conductor can generate heat energy when charging and generating heat always results in energy dissipation and loss of battery.

3. The voltage loss. Lithium battery discharge voltage is not invariable, the safety of the discharge voltage range is 4.2 V to 2.75 V, the power conversion will have difference. Generally, discharge voltage range between 3.6 to 3.9 V, can release the battery 80% or higher power, and if outside this range, power consumption will be increased.

　　
4. Power supply loss. When Power Bank works, it not only charging the battery but also charging other components of mobile phone, especially the screen, which is the biggest power consumption.
　
5. Operation loss of Power Bank. When Power Bank works, it need power to keep operation, the power also provide by its internal battery.

After deducting above loss, the capacity reaching into mobile phone’s battery will be around 85% of 4440mAh, which is 3774mAh. This 85% is what they called conversion rate of Powerbank, which is not the overall conversion rate. From the 6000mAh to the actual output 3774mAh, it loses about 37% capacity. Namely, the actual transfer efficiency just around 63%. The following picture can help us know how many times will be 6000mAh Power Bank charging for mobile phone.

6000mAh Power Bank real charging times

Formula: Charging times= Power Bank capacity ×3.7V×conversion rate (85%)÷5V÷mobile phone capacity. 

Why 2GB USB Flash is 1.75G-1.85G only showing in computer?

Every product has its reasonable price range. As factory, we offered price is from accurate cost accounting, with reasonable profit. If the price you get is much lower than us. Its must sacrifice the quality of product. Below is the very import factors which influence the cost of power banks..

1. Capacity of Power Bank
Our Power Bank is real capacity as our nominal capacity. Such as 2600mAh Power Bank, Some factories use the lower capacity cell inside of 2000mAh, 1500mAh or even 1000mAh only.

2. Aging testing for Power Bank 
Aging test is the key point of dramatic difference between the quality and price. 

What is the meaning of the Power Bank ageing testing? 
Ageing is to test the effect of charging times and maximum activate lithium ion battery inside. Make the battery have no memory effect.
More than 8 hours aging test, excellent quality ensured. Our engineer is 100% check every single Power bank follow battery industrial’s most strictly test process; make sure every single product is safe and reliable. 


Many factories haven’t aging testing for the products, these Power bank without through aging testing is unstable, it’s May not able to charge after using several times. 

3. Overload protection system of Power Bank, the crucial point of the safety

Our battery protection system has Over-voltage, under-voltage, overload and short circuit protection function. This is basic and crucial guarantee of using safety.
In order to cut-down the cost, some factory’s products even have no the protecting device inside.

 

 

 

 

 

 

The account of USB Drive’s capacity

Key Word ：FLASH Memory , BLOCK , FAT 

Flash memory is a solid-state, non-volatile, rewritable memory（NAND FLASH） that works like RAM and a hard-disk drive combined. Flash memory stores bits of electronic data in memory cells, just like DRAM and SRAM, but flash also works like a hard-disk drive because when the power is turned off, the data stays in memory. Flash memory is becoming increasingly popular for portable computing and communications applications.
By the original manufacturer design, The Flash memory make up of block. For example,128MB can be divided with 1024 blocks ,as the follow：


vided with 1024 blocks ,as the follow：


128Mbyte divided 1024 blocks ,and 1 block divided with 64 page
1 Page divided with 2K+64 bytes
But manufacturers use the account is that 1M =1000 M ,1K=1000Byte . 
By this account，The capacity of 128MB can be accounted as follow ：
128MB = 1024（block）*64（page）*2000（byte）=131072000 bytes
As we know the computer use bytes as a unit to account disks capacity.
The computer use the account is that 1MB=1024K 1K=1024Byte 
By this account，128M=1024*1024=1311768576 bytes. that we see the actual capacity is
131072000/（1024*1024）=125MB

But in fact，there are bad block in product process. A few bad block can be allowed. But the bad block can’t be used，Bad blocks will be deducted from the 1024 good blocks. As hard disk, USB drive also uses FAT or FAT32 file system. FAT file system include MBR main boot partition，FAT file config table and ROOT directory. There will use a few capacity，several Kilo Bytes as general .(The capacity is more larger the lost capacity )，while USB controller will use 10 blocks as spare space for bad block of future using. In order to sure the stability of products, most big manufacturers (such as Toliba, SONY, ect.) always keep above 10 blocks to ensure the stability. The capacity of 125MB will be occupied 1~5M because of above reason. The capacity of 128M Flash memory is impossible to show on computer as 128MB(1311768576 byte).

The hard disk manufactures (as MAXTOR，WESTWOOD，HATACHI) all use the same way to account the capacity. A 80GB hard disk, the actual capacity of 76GB only. 

Below is the capacity standard of Sunny-Tech:

1GB-960M-975M
2GB-1800M-1900M, show in computer is 1.75G-1.85G
4GB-3800M-3842M, show in computer is 3.7-3.75G
8GB-7600M-7900M, show in computer is 7.4-7.75G
16GB-15155M-16076M, show in computer is 14.7G-15.7G

Why Power Bank’s prices are big difference from different factories?

Every product has its reasonable price range. As factory, we offered price is from accurate cost accounting, with reasonable profit. If the price you get is much lower than us. Its must sacrifice the quality of product. Below is the very import factors which influence the cost of power banks..

1. Capacity of Power Bank
Our Power Bank is real capacity as our nominal capacity. Such as 2600mAh Power Bank, Some factories use the lower capacity cell inside of 2000mAh, 1500mAh or even 1000mAh only.

2. Aging testing for Power Bank 
Aging test is the key point of dramatic difference between the quality and price. 

What is the meaning of the Power Bank ageing testing? 
Ageing is to test the effect of charging times and maximum activate lithium ion battery inside. Make the battery have no memory effect.
More than 8 hours aging test, excellent quality ensured. Our engineer is 100% check every single Power bank follow battery industrial’s most strictly test process; make sure every single product is safe and reliable. 


Many factories haven’t aging testing for the products, these Power bank without through aging testing is unstable, it’s May not able to charge after using several times. 

3. Overload protection system of Power Bank, the crucial point of the safety

Our battery protection system has Over-voltage, under-voltage, overload and short circuit protection function. This is basic and crucial guarantee of using safety.
In order to cut-down the cost, some factory’s products even have no the protecting device inside.