Test/Review of USB meter: KCX-017

USB meter: KCX-017

Official specifications:

  • Input voltage : 3V-7V
  • The input current : <3.5A
  • The display : voltage, current, discharge capacity ( total of 10 groups can be stored )
  • Current can be calibrated

I found this unit on Ebay at a dealer called missjun2010

How does it look

The button is used to select memory with:
One long click: Select next memory and clear it.
Double click: Enter view mode.
Click in view mode: Show next memory.

The device has the usual usb connector for input, but also a micro usb connector that can be used directly with any standard usb charger.

I could just pry it open.

On the topside there is only the LCD display with a background light and a switch.

On the bottom there is a PIC microcontroller, a HOLTEK LCD controller, a opamp and two 50mOhm resistors in parallel, i.e. 25mOhm resistance.
This is a very nice low resistance, but is partially spoiled by the cable.


  • Display starts flashing when voltage gets below 4.7 volt, but there is a delay.
  • Display starts flashing when voltage gets above 5.3 volt, but there is a delay.
  • Internal resistance is about 0.16ohm including connection resistance.
  • Voltage display is within 0.04 volt in the 3.0 to 6.0 volt range.
  • Current display is within 0.02 ampere in the 0 to 3.0 ampere range.
  • The device has 10 memories for mAh. Press and hold button to select next.
  • To view mAh memories double click button and the press it to change between memories, to see last saved values requires 10 single clicks.
  • Own current consumption is 6.5mA
  • I tried to calibrate it, but did not succeed in changing the factory calibration.
  • USB data works fine.

M1: 32,9°C, M2: 38,1°C, M3: 39,7°C, HS1: 49,0°C

There is nothing in the device that gets hot.

M1: 34,4°C, M2: 35,1°C, HS1: 42,1°C


I am not very impressed with the memory feature, but it can be ignored. The current display is fairly accurate and it has an acceptable resistance.
I will call it a good usb meter.


How do I make the test

here i present my review of the KCX-17. powerbank is 1x18650 3000mAh cell. smartphone has 3200mAh cell; in hobby charger i get 1393 for 1.00A charge, and 1439 for 0.50A discharge, very good.

charge/from mains PC powerbank notes




















no explanation
phone current 1.33A (0.00A) 0.42A (0.06A) 0.42A (0.42A) no observation







N/A no comments
current 0.70A (0.00A) 0.82A (0.00A) no notes

I like this one a lot because of the microusb in feature. It let’s you measure chargers that have the cable built-in to the wall wart.

I agree though, the memory part isn’t very well thought out

I recently got two of these from Fasttech.

The memory feature is a bit of a non-issue for me since if I'm tracking mAh I usually just long-press to clear the next available memory and then record the results in SimpleNote when I'm done. It's worth noting that the device will store the memory reading even if the source cuts out - such as running down a USB battery pack to test capacity. When connected to a new USB source, the cut-off reading is preserved which I find useful.

The only problem I've had so far is that one of my units has a nice bright display while the other is very dim and hard to read.

Other than that, I'm happy to see this unit professionally reviewed and I'm planning to get a couple more for my small solar projects.

Thanks HKJ.

Hello HKJ,

I’ve read your reviews and went ahead to order one KCX-017 and one Xtar VI01 USB Current/voltage detector.

When using Anker’s 40W charger with KCX-017+iPhone’s Lightning Cable to charge my iPhone 6 Plus,

  • It reads ~5V/~1.05A-1.2A.
  • Stops charging at 98%.

When using Xtar’s VI01,

  • It reads ~5V/~1.3-1.5A
  • Charges till 100% and then some

I’m curious as to why they both perform differently (especially in Amperage). Have you tested both to see which one is more accurate than the other? Am looking for possibly the most accurate USB doctor but none of your reviews have met that criteria that I believe you have so you just pen them down as a good usb meter.

paul, the very good ones are expensive:

Difference in performance will usual be due to difference in internal resistance and connection resistance (A lower value is better).

You can usual get a good idea about accuracy by checking the included table with measurements, but it is not really possible to say a device is generally accurate, just because my review copy performs fine. The best way to evaluate precision is to look at the public specifications and see if my review copy stays within them.

The best one for current measurements I have tested is probably this: http://lygte-info.dk/review/USBmeter%20Portapow%20UK.html

The YZXStudio is also interesting, but I have not tested it: http://www.ebay.com/itm/USB-2-0-LCD-Power-Monitor-Green-YZXstudio-ZY1263-QC-3-0-18-bit-Power-Meter-/171969412327

Seems like tests have been done. Has the YZXStudio beat PortaPow?

Also, how do I use this KCX to track my power bank’s capacity? I have a 1-3A load resistor but I get different readings with different load ratings. Does 1A load = 1mAh?

For usb the YZX has the advantages with better functionality and lower resistance, but they cannot be used for other stuff.

Capacity will vary with current, the boost converter will have better efficiency at lower current and the battery will deliver more power at lower current.
It is not really importance if you use 1A or 3A load, just always use the same.

Not really, you will add considerable DC resistance. That is not the case with Portapow.
Portapow do also have a few other advantages, it only loads uA, not mA and it can be used as a voltmeter (More interesting with a uA load, than with a mA load). As a general capacity/power meter for lower DC voltages I like it better, but as I wrote above it cannot match YZX for usb usage.

Because I have measured a lot on usb connectors and cables, portapow uses much better connectors and cables.

Yes, some usb meter can be used with other stuff if you buy/make adapters, portapow is supplied with connectors for other stuff.
Portapow supports higher voltage and current than usb meters, again something that makes it more useful for other stuff.
A usb meter would likely die if you swap polarity with you adapters, portapow will just stick a - before the voltage.

When using converters, you create additional resistance by using them when measuring. Especially the 1$ cheapo converters. The quality and thickness of the cable is unknown, so is the quality of the connectors and their attachment to the cable. All things that do influence resistance.
I am doing a test of a lot of micro-usb cables at the moment, you won’t believe the voltage drop some of ’em exhibit. And that has all to do with what I describe above.

That sounds like an electrician that only knows about AC. For low voltage DC it is much cheaper.

I am also benchmarking micro USB cables with my Samsung S5 G900F, the truth that very few are aware about, this is that any such cable will never carry more than 1.6A , simply because micro USB female plug specification this forbids any higher current than 1.7A

That is wrong, some devices draws more than that from micro usb.
Typical rating for micro usb connector is 1.8A, but there exist connectors rated for 3A.

I look like you lack knowledge about electronic.

Micro usb connectors are used for much more than phones, there are also some phone manufacturers that may want to use higher charge currents, most good chargers today support between 2 and 2.5A current.

CC/CV mode do not really have anything with counting the mAh to do. I have not seen any meter getting slow or helpless, but I will not be surprised if there exist one or two that do :wink:

It sound like you are: New user that starts by posting silly claims, instead of posting something useful.

I see no reason to post any links, you can just start reading some of my stuff.
For higher current on usb check some usb powered chargers.

You have obvious not figured out what I do.
A few of my cheap toys: My lab setup

First time I have seen this description for a type C connector: USB Connectors WR-COM USB Micro SMT Type B Horiztl

And specifications says 5 contacts.

The B is the one used in phones and that the above datasheet show 3A for.

USB type-c is not called micro.

Seems the specs are on the back of the meter are a little bit on the safe side :

Hold up… Don’t get your panties in a twist, kiriakos.

I have changed the title of the video and took out the Quick Charge statement.
I do show in the video that the meter does show higher voltages. That was all I wanted to share.

But, I have to say, I have to agree with gauss163, I do not fully understand what you are trying to say, and I do not like the tone of it either.

I did the test, to the best of my abilities, using the gear I have at hand.
Moreover as the load (YZXStudio ZL1000) does support 9V and 12V QC, and the power supplie supported both QC2.0 and 3.0 I may have concluded too quickly and wrongly, that the meter did read QC. As was pointed out here rather crudely, that was not the case, and I have changed the title of the video accordingly.

As for your comment on stealing the thread from HKJ, I thought this was a forum and not a blog.
I am inspired by HKJ for my research and check his reviews often before buying things.

And as for your blanket statement earlier about micro-usb cables never carrying more than 1,6A :
I know of at least one :

And a port that takes more than 1,7A too, whaddayaknow.
These may not be $1500 dollar meters, but it ain’t $5 eBay crap either.