Xiaomi ZMI power bank QB821: one of the best power banks with fast charging QC 3.0

by Kelvin
Xiaomi ZMI power bank QB821: one of the best power banks with fast charging QC 3.0

Overview of a suitable external battery from the ZMI line. The QB821 model is equipped with two outputs with QC3.0 and power up to 18W. Inside, a 20,000mAh (74Wh) Li-po battery is installed. The QB821 model comes in several colors, I really liked the white version with a textured body and a dot (DOT-matrix) display.

Specifications:

  

Product name 20000mAh ZMI Power Bank
Model number QB821
Battery capacity 20000mAh 3.7V (74Wh)
Battery type Li-polymer Battery
Input interface Micro USB & Type C
Output interface Double USB & Type C
Input DC 5V / 2A, 9V / 2A
Ouput 2 x DC 5.1V / 3.6A, 5.1V / 2.4A 9V / 2.0A, 12V / 1.5A, MAX 18W

Powerbank is very powerful and thoughtful. Inside installed a new generation of electronics. The image below shows a list of different protections and locks that a power bank is equipped with.

Comes paverbank in company packaging

There is a ZMI logo and an image of the QB821 modelOn the back there is additional information
Inside an extra cardboard box for protectionPresent branded hologram ZMI

Please note that the kit has a nice universal cable

Both Type-C and MicroUSB at the same time

ZMI Appearance and Image QB821

Panel with connectors has several outputs and inputs

Pay attention to an interesting animated indication

It shows not only the charge level in digits in% …… but also the direction (output-input) of work

On the case there is a ZMI logo

On the back, detailed specifications

For comparison ZMI Power Bank 10000mAh external battery with QC2.0 9V / 12V (QB810) technology support

With smartphones and powerful consumers, she works on Hurray.

An example is work. USB soldering iron (18W) from this power bank.

I start testing the outputs.

Test in 5V 1A mode

Test in 5V 1.5A mode

Test in 5V 2.0A mode

For the second output, similarly: 5V 1A

And 5V / 2.0A

Test in 5V 2.4A mode (maximum load on one output)

I start automatic testing of fast charging.

Testing in 9V 2.0A mode

Testing in 12V 1.5A mode

Checking QC3.0 trigger. Set arbitrary voltage (6.7V)

I note that the external battery operates in the charging mode with low currents (~ 40mA)

B end-to-end charging supported

The full capacity test showed full compliance with the declared characteristics (74Wh)

Check on a charge (about 19000mAh, 97 Wh taking into account efficiency)Check for discharge: 76Wh and 15000mAh. Stated 12,600 mAh and 74Wh.

By the way, the QB821 external battery has the ability to recharge itself with QC3.0

At the end of the review, I can say that the ZMI QB821 model is an honest 20,000mAh power bank. Two powerful outputs provide simultaneous operation of two devices. Support for QC fast charge protocols is convenient for modern smartphones.

It is also ideal for powering powerful devices, such as USB soldering iron.

Now ZMI QB821 is for sale at a promotional price, you can purchase it on Aliexpress.

The topic is interesting, there is even a large selection of power banks in this article

A selection of the best power banks (external batteries) with support for QC3.0 and PD

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