TENOZEK USB Power Bank 4000mAh



Official specifications:

• Material: Alloy
• Output: Dual Output Connections
• Output: 5V 2.1A
• Type: Emergency/Portable
• Battery Type: Polymer Battery
• Color: Silver
• Dimensions: (4.72 x 2.36 x 0.39)" / (12 x 6 x 1)cm (L x W x H)
• Weight: 4.41oz / 125g
• Input: DC 5V 1A
• Battery Capacity(mAh): 4000

I got it from tmart.com

How does it look



The power bank is delivered in a clam shell, this looks to be a fairly universal box, that is used for multiple models.



Contents was the charger and a usb cable, no instruction sheet.




A micro usb cable is stored in the charger.





The micro usb connector is store in one end of the charger, the other end has a normal usb output, a micro usb charging input, a power gauge with a button to activate the gauge.







Measurements

• Both Usb output is coded as usb charger (DCP)
• Both outputs are in parallel.
• Output is always on, except when charging.
• Size: 115 x 59.4 x 10.5mm
• Weight: 122g (Accessories not included)

The box can deliver 1.2A before the output starts to drop and at about 1.5A the overload protection kicks in.



The micro usb looks the same, but the voltage is slightly lower due to the cable.



Running the two outputs in parallel gives the same result, but with a bit more voltage, due to the parallel connections.



The capacity at 5V is about 2800mAh, this is very good for a 4000mAh battery bank. At this load the voltage looks fine.



Increasing the load to 1A shows that the boost converter do not have any spare capacity. It can handle 1A, but is at the limit of its capacity when the batteries are about empty (The voltage drop during the last few minutes).
It can deliver 1A for 15 minutes less than 3 hours.



Using a 1.2A load shows clearly that the converter cannot handle more than 1A.
Note: This test was not done on a full pack.



Noise is 15mV rms and 115mVpp



Noise is 25mV rms and 153mVpp, this is low values.



Charge current is a bit below 1A and it looks like the charger uses a CC/CV charge algorithm.



A 0.5ohm resistor in series with the usb supply to simulate a weak power supply or long cable makes the charging slower.




Conclusion

The power bank is a nice small one and can deliver the rated capacity, has low noise, but the specifications on it is a bit too optimistic, it is not a 2.1A device, but a 1A device.
The build in micro usb cable works nicely and means that there always is a cable available.

I will rate it fairly good.


Notes

The power bank was supplied by tmart for a review.

Read more about how I test USB power supplies and chargers