Part 1： PN-910 testing
Part 2： 20000mAh powerbank testing
Part 3： Lithium-ion / polymer Li-Po （not 18650 type）
Part 4: Xiaomi Powerbank tested

Part 1: PN-910 testing

I had carried out a test, this powerbank had discharged for 7 hours 20 minutes（4.925V, 0.945A)

i use two 10ohm resistor in parallel , resulting total resistance of 5 ohm, resistance is enough low to get the output of 4.925V，0.945A.


two 10ohm resistor in parallel


display show a little of fluctuation，between 4.92-4.93V, 0.94-0.95A. on average, it is 4.925V，0.945A.


Inside the case contain four 18650 type battery, each one contain 2800mAh of capacity.


measurement taken by vernier calipers, diameter is around 19mm.



The powerbank in the current market are measured by mAh, of course the higher the better.
But, mAh cant reflect the real capacity of a powerbank, why?
Because most of the powerbank is using lithium ion battery, voltage is 3.7V, after fully charge is 4.2V.
When you are using it to charge other devices, its output voltage is at 5V. (USB device must be 5V)
This mean that the 3.7V should be converted into 5V before it can charge or operate other usb devices.
An example, for 11200mAh powerbank,
3.7V x 11200mAh = 41.44Wh = 5V 8288mAh
So we are more concern on 5V output, that is 8288mAh
The conversion is not 100%, there will be some losses about 10% or more.
just take 10% as losses, so we have 8288 x 90% = 7459.2mAh @ 5V
if your handphone battery is 1800mAh capacity, it mean that it can charge your handphone for about 4 times.

what i tested here, i am measuring using power and not mAh, which is accurate.
As you know, VXI= Power
Under 5ohm load, 4.93VX0.94A=4.6342Wh
Because of the measuring time is quite long, i take measurement on every half hour.
Total discharging time is 7 hours 20 minutes.
From calculation, i can get a total power dissipation of 34.13Wh,
the rated power is 41.44Wh ( 3.7V x 11200mAh)
34.13/41.44x100%= 82.36% is the real capacity

This is one kind of fake powerbank.

(shared on facebook, just for comparison)

Just avoid this type of powerbank, even inside is not filled with sand, its capacity is very much lower than the rated capacity.
My tested powerbank has 11200mAh capacity, HxWxL: 21.5mmx71mmx110mm
Each 18650 is around 18mm in diameter
length of 110mm can fit a capacity of 11200mAh, what is the length of powerbank to fit 20000mAh or 30000mAh? you can do the calculation.

Beware, there exists of fake powerbank which is same as what i tested. The one i tested is 100% original.

This post has been edited by x-treme: Jun 4 2014, 09:18 PM

Part 2: So called 20000mAh powerbank test

i had borrowed 20000mAh powerbank from my friend. Due to warranty reason, my friend not allow me to open it.
tried some method to figure out how many 18650 battery inside the powerbank, lastly i use torch light and saw there are 6 18650 battery.
What is the capacity of each 18650 battery i'm not sure, but i can test and prove it.



Written 20000mAh, made in Taiwan
Written 2 output current: 2.1A and 1.0A. After i tested, it is just a parallel output from same source, not separated.



This set up is similar with my part 1 test, using 2 10ohm resistor in parallel, resulting 5ohm resistance.
Output current stable: 4.79V, 0.94A


Result are recorded, total discharge time is 4 hour 40 minutes. Total output power is 21.01Wh, only 28.4% is the REAL output power.
Rated capacity is 3.7V X 20000mAh = 74Wh (vs 21.02Wh Real)

[My tested PN-910 had discharged for 7 hour and 20 minutes, total output power is 34.13Wh, 82.4% is the REAL output power]
Rated capacity is 3.7 x 11200mAh = 41.44Wh (vs 34.13Wh Real)


The 20000mAh powerbank had been tested for twice because the first time test i had over estimated it can discharge for at least 5 hours.
But it is actually less than 5 hours.

Dimension measurement by vernier calipers（20000mAh）：135mm x 71mm x 24mm
(my friend said this unit was selling with price tag of RM110)

This post has been edited by x-treme: Apr 29 2013, 11:48 PM

PART 3: Lithium-ion / polymer （not 18650 battery，18650 is similar to AA type of cylindrical battery）

Borrowed another powerbank from my friend， it say it is using Li-Po ，smaller and thinner size.（diameter of 18650 battery is 18mm，this one is less than 18mm thickness）
The rated capacity is 5000mAh，everyone can guess how much is the real capacity?


Battery inside is thin, but is it soft one, if you press it, it will not restore back to the original position.


The voltage regulation is not good as PINENG powerbank, it fluctuate much more.
Some of the data taken:
4.77V 0.92A
4.80V 0.93A
4.64V 0.89A
4.48V 0.86A
4.37V 0.84A

From my calculation, the real capacity is only1.82W
Rated capacity 3.7Vx5000=18.5W only9.84% is the real one.
this powerbank had been used for 1 year plus, now only remain 9.84%，1.82W even can't charge iphone for half time.

For your information
Even though there aren't sand inside the powerbank, it doesn't mean it has real capacity.
For example: I opened a powerbank, inside contain 4 pcs of 18650 battery, if I said each 18650 battery has capacity of 10000mAh, 4x10000= 40000mAh. This can charge note 2 more than 10 times. Will you believe it? Don't laugh, there are people will believe this.
Remember the highest capacity of 18650 battery is 3100mAh，manufactured by Panasonic. Those who said it has 5000 or 10000mAh are cheating.[/size][/backcolor]
If the powerbank is not using 18650 battery, but is Li-Po type, the price is much higher than 18650 type. Li-Po is extra thin and slim. Manufacture price also higher. Those who sell at cheap price, you know la

Another sharing
Anyone can guess what is this ?

It is battery but not AA type，is 18650 battery，it is used in our laptop battery, this is called 6-cell type.
This battery I disassembly from Lenovo laptop, rated capacity is 48Wh, each 18650 battery contain 8Wh, or 2162 mAh.

Everyone can see that even laptop also use 18650 battery, don't think that this type of battery not good, it is cheaper than Li-Po type.

This post has been edited by x-treme: Apr 29 2013, 11:48 PM

On the first sale of Xiaomi in Malaysia, I managed to grab 2 units of powerbank.
Last week I just get the unit delivered by UPS.
This time I carried out the test using a battery tester, no longer using the manual way to calculate the capacity, because it consumes a lot of time if calculate manually.

Let's take a close look at Xiaomi powerbank. The case is made using aluminium.
The weight is a bit heavier than the Pineng PN910 (also contain 4 cells)
This Xiaomi powerbank carry a capacity of 10400mAh, which is 2600mAh per cell.
I not sure whether my unit is made using LG or Samsung brand as I don't want to disassemble the unit.
Spec:
Input 5.0V 2.0A
Output 5.1V 2.1A
Rated capacity: 3.6V 10400mAh / 37.44Wh



Ok let's start the first test. Although Xiaomi powerbank capable to output 2A@5V, I want to test for 1A output to compare with Pineng PN910. (since different output current will affect its efficiency)

Updated test for 1A@5V
Voltage during discharge 4.97V


Current during discharge 1.00A


The result is here 7 hours 9 minutes.
7.15x4.97x1.00=35.5355Wh
35.5355/37.44= 94.91%



This post has been edited by x-treme: Jun 22 2014, 08:58 PM

The next 2 days, after fully charged the xiaomi powerbank, I carried out the second test.
I used 2A discharge so I can shorten the test time(Now working already I have limited time do the test)

Voltage during discharge @2A


Current discharge set at 2A


Total discharge time 3 hours 41 min.


Capacity measured @ output voltage 4.85V is 7390mAh



Calculation using time- 3 hours 41 min
3.68hours X 4.85V X 2A =35.696Wh

Calculation by capacity measured
7.39Ah X 4.85V= 35.84Wh

So we use this value 35.84Wh/37.44Wh x 100% = 95.73%

I really can't believe even at high current output 2A it does give the efficiency above 95%

The unit did not getting warm when discharging @1A but it get hot when discharging @2A.
The aluminium case helps a lot to dissipate the heat to keep the component cool.

Anyone tested the Xiaomi powerbank can share with us.


This post has been edited by x-treme: Jun 4 2014, 09:17 PM

Pineng PN910 powerbank tested again after 1 year 3 months.
I no longer using the manual way ( 2 multimeter and resistors) because it consumes a lot of time when testing.
Now I using the tester unit which is capable to test car battery, lithium battery or powerbank etc.
Thresold voltage, discharging current can be manually adjusted. It is much more accurate than my test last time.
Ok, now let's see the 1st result what we got here. The testing are based on 2.1A output port.

I discharge the powerbank using 1A current setting.


The voltage@1A output which is 5.05V


What I got the result here. 6 hours and 10 minutes.


5.05V x 1.00A x 6.167hours = 31.14Wh

rated power= 41.44Wh

31.14/41.44 x 100% = 75.14%

The next test is discharge using 2A, which I never test before.

I discharge the powerbank using 2A current setting.


The voltage@2A output which is 4.70V


What I got the result here. 2 hours and 31 minutes.


4.70V x 1.99A x 2.52hours = 23.57Wh

rated power= 41.44Wh

23.57/41.44 x 100% = 56.88%

Conclusion is the battery starting to degrade after 1 year of usage.
The conversion efficiency is poor on 2A output, compared to 1A output.
Xiaomi have better efficiency than that.

This post has been edited by x-treme: Jun 10 2014, 01:56 PM

this brand PINENG quite good, from what i have tested.

you can find in mobile accessories ...

yup. for the 18650 size of battery, the highest capacity is 3100mAh, but it is expensive than 2600 and 2800 type. for those cheap powerbank they wont use that 3100mAh. only use around 2000-2400 like that or even lower capacity, so it can save cost. but if it using Li-Po type, it wont be so cheap also.

there exist 20k or 30k capacity, but it is big and expensive, rm300-500 or more. this type can be used for charging laptop.

self discharge i can't test. so i don't know.
the "how long" is depending the rate of flow of the current to charge the phone.
for an example, my phone accept the current rate of 950mA therefore 1.84 hour can fully charge my 1750mAh battery in AC charging mode.
my phone accept 450mA current rate for usb charging mode. it will take longer time.

So it is depend on which mode you are using to charge your device.

i din't heard that brand before. And i saw there is 73% why don't you doubt it ? sell without earning ? i can say the original price is cheaper than 109.

For me, whatever brand, the REAL original is the best, the FAKE original always the worst one.
The reason why the REAL original Yoobao is more expensive because it is more famous.

as long it is original, brand didn't make much different.

for example, yoobao 11200mAh and pineng 11200mAh. Do you think yoobao will give higher capacity than pineng 1 ? actual capacity only different in few % only.

PN910. high capacity at affordable price.

that one i can't comment much. how you want to measure the built-in quality?
but for battery it is using the real capacity.
those not made in china one, you know the price.
with the same spec it can double the price.

i don't know how to differentiate those grade A B C.
of course if you buy the better cell, it will last longer, and it will cost more.
nowadays many powerbank in the market are with fake capacity. for example 30000mAh
how can a 6cell / 8cell powerbank equip with 30000mAh?

so had you tested for the real capacity for the yoobao 6600mAh and the efficiency ?
how about the grade B ? 80% ?

now i very hard to believe those.
many things have imitation.

haha. so did you buy the original yoobao ?
now you are going to replace the battery by yourself ?
by the way my gf is taobao agent too. i can buy anything from taobao, can ask them how to pack also.
there are something powerbank, which can replace battery by your own. i am planning to get one to test.

about these you can refer to batteryuniversity for more information.