ZMI QB820 Review



Disclosure: As an Amazon Associate I earn from qualifying purchases. I purchased the product in this review.

ZMI QB820 – A laptop friendly power bank with a USB hub function

Model: QB820

ZMI QB820 ports and specs

ZMI QB820 ports and specs

Tech Specs:

  • Ports: USB-C, USB-A x2
  • USB-C Output:
    • 45W USB-C Power Delivery 2.0 (5V/3A, 9V/3A, 12V/3A, 15V/3A, 20V/2A)
    • Quick Charge 3.0
    • Samsung Adaptive Fast Charging
    • Huawei FCP
    • Apple 2.4A
  • USB-A Output:
    • 12W USB (5V/2.4A)
    • Quick Charge 3.0
    • Samsung Adaptive Fast Charging
    • Huawei FCP
    • Apple 2.4A
  • Input: 45W USB-C PD (5V/3A, 9V/3A, 12V/3A, 15V/3A, 20V/2A)
  • Capacity: 20,000mAh | 74 Wh
  • Size: 6.3 × 3.2 × 0.8 inches | 160 × 82 × 21 mm
  • Weight: 14.3 oz | 405 grams

Learn more about USB Fast Charging Standards.

ZMI QB820 box and contents

ZMI QB820 box and contents

Included In Box:

  • ZMI QB820
  • USB-C to USB-C 2.0 cable, 20 inches
  • micro-USB cable w/USB-C adapter (56k Ohm resistor)
  • Pouch

Good For:

  • Commute
  • Travel
  • Fast charging:
    • iPhone 8/X
    • USB-C PD Android phones
    • Quick Charge Android phones
    • iPad Pro
  • Nintendo Switch (handheld & docked)
  • 12-inch laptop
  • 13-inch/14-inch laptop
Top: Anker PowerCore Speed 20000 PD. Bottom: ZMI QB820.

Top: Anker PowerCore Speed 20000 PD. Bottom: ZMI QB820.


  • USB hub function for laptops
  • Supports lot of fast charging standards
  • Supports pass through charging
  • Includes a USB-C to USB-C cable
  • Charge two devices at once
  • Within FAA limits for lithium batteries and flights


  • Fast charging standards over USB-C is against USB-IF specifications
  • Limited to 40W for some laptops

Actual Capacity

All power banks list their capacity (mAh) based on the nominal voltage of the battery cells. It does not accurately represent how many recharges you’ll get with the power bank. Actual capacity shows how much power you’ll actually get from a power bank.

You can divide the actual capacity below by your device’s battery capacity. That will give you a realistic estimate on the number of charges it will provide.

  • Listed Capacity: 20,000mAh
  • Actual Capacity:
    • Phone Charging: 13,000mAh
    • Switch Charging: 12,300mAh
    • Laptop Charging: 9,200mAh

Actual capacities are estimates are based on capacity testing and calculation.

First Impression

The ZMI QB820 has a good size and weight for its capacity and output. Curved edges on all sides make it comfortable to hold. And the included travel pouch, large enough for the power bank and cables, is a nice extra. Its output and USB hub function (details below) make it a nice choice for small to mid-sized USB-C laptops.

Power Meter Readings

iPhone 8
iPhone 8 power meter

iPhone 8 power meter

iPhone 8 power negotiation

iPhone 8 power negotiation

The iPhone 8 fast charges when using a USB-C to Lightning cable. We see the usual power negotiations. Connection starts at 5V, then moves up to 9V. Learn more about fast charging iPhones.

Both the USB-C and USB-A ports also supports Apple 2.4A. That is an older fast charging standard, but it still works with newer iPhones. And it’ll provide a fast charge for older iPhones that don’t support USB PD. It charges near the same rate as USB-C PD when the iPhone’s battery is 30% or more charged. It is 1-2W slower at lower levels, but still faster than normal charging.

Moto G6
Moto G6 power meter

Moto G6 power meter

Moto G6 power negotiation

Moto G6 power negotiation

The Moto G6 fast charges using the Quick Charge ports (either USB-A). This will be the same for Samsung and Quick Charge enabled Android phones. The USB-C port also supports Quick Charge 3.0. But the Moto G6 only charged at a normal rate, half what it did using the USB-A ports. Motorola doesn’t use Quick Charge, its TurboPower tech mimics it. So 100% compatibility isn’t guaranteed. Samsung and proper Quick Charge enabled Android phones may see better results. But no better than when using the USB-A ports.

The Google Pixel and Android phones that support USB Power Delivery will fast charge on the USB-C port. Learn more about fast charging various Android phones.

Nintendo Switch
Switch gaming power meter

Switch gaming power meter

Switch sleeping power meter

Switch sleeping power meter

Switch power negotiation

Switch power negotiation

The Nintendo Switch charges at its max rate, charging while you play. Its charge rate while sleeping is also normal. This charger can also power the Switch’s dock. Learn more about charging the Switch.

The PD protocol negotiation with the Switch is typical. It connects at 5V and moved up to 15V after negotiations. Current steps up once the 15V connection is made.

You can read my review of this power bank specifically for the Nintendo Switch at Switch Chargers.

MacBook Pro, 13-inch
MacBook Pro 13-inch power meter

MacBook Pro 13-inch power meter

MacBook Pro 13-inch power negotiation

MacBook Pro 13-inch power negotiation

As a 45W charger it can support 12-inch laptops. As well as 13-inch models running office, Internet, and entertainment apps. If playing video games or using CPU intense apps it may only extend battery life. But either way you get a lot more uptime. It is worth noting that 45W is available at 15V, but only 40W is available at 20V. You can’t force your laptop to use 15V over 20V. Depending on your model you may see the slightly slower 40W charge. Learn more about charging USB-C laptops.

Compared To Similar Power Banks

ChargerZMI QB820dodocool 20100 45W Type-C PDOmars PowerSurge 20000 45W USB-C PD

RAVPower 45W Super-C 20100
Output45W USB-C PD
Quick Charge 3.0
Quick Charge 3.0
USB-A x2
USB-A x2
USB-A x2
FeaturesPass Through Charging
LCD shows remaining charge
Pass Through Charging
CableUSB-C to USB-C cableUSB-C to USB-C cableUSB-C to USB-C cableUSB-C to USB-C cable
Dimensions6.3 × 3.2 × 0.8 in
14.3 oz
7.4 x 2.6 x 0.9 in
17.1 oz
7.1 x 3.1 x 0.9 in
19.8 oz
6.3 x 3.1 x 0.9 in
14.1 oz

Prices are from Amazon Product Advertising API, last updated on 2019-05-26.

You can see more USB-C power banks here.

ZMI QB820 with Moto G6

ZMI QB820 with Moto G6

ZMI QB820 with Nintendo Switch

ZMI QB820 with Nintendo Switch

ZMI QB820 with MacBook Pro 13-inch

ZMI QB820 with MacBook Pro 13-inch

USB Hub Function

The USB hub function in the ZMI QB820 allows you to use the power bank to connect USB-A devices to your USB-C laptop. This is normally done using a separate USB-C to USB-A adapter.

  1. Connect the ZMI QB820 to your laptop via USB-C.
  2. Connect your USB-A accessory to one of the two USB-A ports on the ZMI QB820.
  3. The accessory will appear connected to the laptop.

Please note data transfer rates are limited to USB 2.0 speeds(480Mbps).

Using the Included USB-C to micro-USB Adapter

As a general rule it is safe to use a USB-C to micro-USB adapter. Such as the one ZMI included. It is an adapter that connects to a micro-USB cable, giving it a USB-C end. It is not safe to use the opposite, turning a USB-C connection into any kind of other connection. That would allow for connections against USB standards, and dangerous to devices. Again, the adapter ZMI included is the good kind.

My USB tester showed the micro-USB cable with USB-C adapter has a 56k Ohm resistor. That resistor is required under USB-IF rules for all USB-C to USB-A connecting cables.

The cable fast charged my Moto G6 at the same rate as a regular USB-C to USB-A cable. Both allowed the Moto G6 to draw 16W from the USB-A Quick Charge port.

Fast Charging Standards Over USB-C & USB-IF Specifications

The ZMI QB820’s USB-C port supports more than USB Power Delivery. It also supports Quick Charge 3.0, Samsung AFC, and Huawei FCP. Their presence on the USB-C connection is against USB-IF specifications.

USB-C includes communication lines, along with power and data lines. The comm lines allow power negotiation without disrupting data transfers. USB Power Delivery uses these comm lines. As does Quick Charge 4+. But fast charging standards which pre-date USB-C do not. Instead they manipulate the data lines to negotiate power. That go against USB-C specifications, as it disrupts data transfers. But one doesn’t use data transfers with a dedicated charger.

In 2016, some USB-C chargers started offering Quick Charge 3.0. A few USB-C focused engineers warned against this practice and cited USB-IF specifications. But the predicted consequences were vague. As it turned out, nothing bad happened. Since then many chargers have operated this way, against specs. But there have been no reports of real world issues.

I have also not run into any issues with these fast charging standards on this or any other charger. But you should be aware of all the information before buying.

If you’re a stickler for meeting USB-C specifications this isn’t a good charger for you. If you’re more pragmatic it works well and has no known issues.

Pass Through Charging

Pass through charging allows a power bank to both recharge and charge a connected device. Some of the energy flows from the wall output, through the power bank, to the device. The remaining energy recharges the power bank itself.

The ZMI QB820 supports pass through charging:

  • Input: USB-C, Output: USB-A

You can use either USB-A port to charge while the power bank re-charges. Quick Charge is disabled during pass through charging. The Moto G6 was able to draw up to 10W, down from its usual 16W using QC.

Pass through charging is useful for overnight stays with limited wall chargers. It is not recommended to do so on a regular basis. It puts more heat and stress on the power bank, which can affect its lifespan. Doing it when traveling is fine. But don’t set this up next to your bed at home every night.


The ZMI QB820 is a personal favorite for when I travel with a laptop. I added a Lightning cable to the pouch and it has everything I need to charge all my devices on the go. My wife actually uses it more, as she has more work trips. Its 20,000mAh capacity allows the it to come in a reasonable size and weight. And it is less likely to run into international travel restrictions.

Its 40-45W output works well for small USB-C devices on up to a 13-inch laptop. Phones and tablets that support USB Power Delivery can fast charge via USB-C. The Nintendo Switch charges while you play. You can even power the Switch’s dock if the need arises.

Quick Charge 3.0 is supported on all three ports. Though I couldn’t get it to work via USB-C using a phone that mimics Quick Charge. All three ports also support Samsung Adaptive Fast Charging and Huawei Fast Charge Protocol. I would expect Samsung phones to charge as fast as possible. Huawei FCP phones will see lower current than with their included charger.

The USB hub function allows you to use the power bank a USB-C to USB-A adapter. It is always nice to carry one less adapter these days. Some laptop owners may prefer if it had 26,800mAh capacity. That would impact the good form factor too much. And 20,000mAh @ 20V is still enough to recharge most small to mid-sized laptops once. For anyone who needs more there are 45W 26,800mAh power banks available.

About ZMI

ZMI has U.S. based support (web, email, phone) and a 18 month warranty. Zimi Corporation was funded by Xiaomi, a large and well respected tech company in China. And growing in the USA. Zimi provides all mobile power accessories for Xiaomi.

Bottom Line

The ZMI QB820 is a great all-in-one solution power bank. By adding a Lightning cable I can fast charge an iPhone, most Android phones, and Nintendo Switch on the go. Not to mention my laptop and small accessories. Not bad for the contents of a 1 pound pouch.

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