Keweisi KWS-V20 - USB capacity meter from China - Not too precise

Hungarian version.

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Update: 2016.02.25 
Its power consumption is 3,82mA, because of the 5V it is around 0,02W.
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Welcome, I thought it would be a good idea to buy on Ebay from China an USB Capacity meter, so I can measure the capacity of my 18650 batteries. I planned to measure it when I charge something from the Soshine E3 power bank.

"Brand": KEWEISI
Model: KWS-V20
20030815 - I can assume this is the manufacturing date? It was on its case... Of course no manual or anything attached.

If I remember well this is also sold on Ebay under different brand names.

The product itself is looks nice with its "all the time" on white backlight. It has only one button which can reset the time counter. This thing does not do anything else than measure the current flowing through it in mAh. It shows the actual current and V . This works well, except that it is a bit inaccurate. It miscalculates easily with +- 0,2 Volts. Under 100mA the measured amount cannot be true. It fluctuates and sometimes it shows 0. On the picture below it shows 0 because nothing is connected to it, it is just plugged into an USB port. So it works but it’s too inaccurate to for example measure the consumption of my mouse or external sound card. However it seems to be accurate with higher currents. The power goes in on one side and it comes out on the other, as simple as that. I decided to build a capacity meter for the 18650s myself with my Arduino. This will be a new blog post.