USB Tester surprises that can go wrong 

Instablaster

You are totally correct. Capacity measurements of the batteries inside a smart phone or USB power bank from the "outside" are usually reading too low. The reason is that capacity only looks at current and assumes that the voltage is identical with the battery voltage. This was true 12V lead acid batteries when capacity became "a thing". but not now with all these DC-2-DC converters in between. We should switch to energy measurements instead that takes voltage into account. I made a video about this ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u-HKEb1DIWw.html

Why wouldn't you expect a different voltage it? The WHOLE idea of QC and PD "Fast Charging" is to increase the voltage to increase the charging power.

Hi Bruno, I ordered one but it has not arrived yet. So, yes, eventually there will be a test of it

sounds to me the easiest way to answer these questions is to get need another USB tester (doesn't need to be fancy)

Hi Richard, That is rather unusual. Out of curiosity, what make and model is your tester?

@@TheHWcave I'd say it was a cheapie looking at it. It's this one. www.amazon.co.uk/gp/product/B07P2J5VTT

Sorry for the late reply. Plugging the phone in caused it to negotiate a higher charge voltage with the power bank. Whether that happens or not depends on the capabilities of power bank and phone but most modern power banks can supply 9V or even 12V when asked nicely using the PD protocol.

I have not tested the FNB38 but from the spec it looks as if it has way more capabilities than any of the (older generation) UM25/UM34 testers. I have tested the newer TC66 which can trigger but it is USB-C only (you would need adapters for other sockets). The TC66 impressed me with its accuracy which is as good as a 5 1/2 digit multimeter but its slightly more than your limit ($26)

Hi Richard, I totally agree with you. Multiple powerbank sockets used simultaneously are something to be very cautious about. Luckily so far the cheap ones (where the 2 sockets are in parallel) don't implement higher voltages and the more expensive ones (hopefully) do it properly. I just tested my XIAOMI 10000mAh and it won't go to higher than 5V if the 2nd socket is in use. If socket1 was 12V and you plug in socket2, it briefly turns both off and then back on at both 5V. That is not quite what you have in mind, i.e. truly independent ports, but it is a safe implementation. Hopefully other manufacturers implemented similar interlocks. It is certainly something one should test, as you pointed out.

Omg, thanks for this comment. This is nothing that have ever occurred to me that it could happen..

It really depends on your needs. If you are doing mostly USB-C get the TC66 and use adapters for other USB types. The TC66 is amazingly accurate and can be externally powered. If USB-C is not your thing any of the testers in that video will serve you. Get the one with the lowest price. The UM34C has one digit less and goes only to 4A (which is plenty enough for standard USB connectors and cables) while the UM25C has a digit more in resolution and goes up to 5A. The USB-C interface on both of these testers is very limited.

A very good question! My only USB 3.0 disk is not powered through USB, it has an external power supply instead. However, I just did a test data transfer using a USB3 cable and a USB 3 port on my computer first without and then with a UM25 in the cable. With the UM25 in the loop, the copying of a 1.1Gb file took 3 times as long (I used different files of same length to avoid wrong results through caching). So, data flow works fine through these USB testers but because the BM25 actually isn't strictly USB3.0 and implements only D+ and D- and not the additional data lines of USB 3, all transfers drop to USB 2 speed. If transfer speed is an issue, you need to look for another tester that fully implements ALL data lines of USB 3. Regarding power, the UM25 will support up to QC3.0 so higher voltages and higher amps to power a disk directly from USB should be no problem if your computer can provide it, of course.

@@TheHWcave Do you know if UM34 has all the USB 3.0 data lines?

Unlike the UM25, the UM34 has proper USB-A connectors (blue) with the additional pins and the manual states it supports USB 3 on those ports (but not on the USB-C ports which are only 4 wires). To confirm I tried the same transfer test explained earlier but it failed after a second or so with an IO error. Now, I am pretty sure that this is NOT the fault of the UM34 because the 3.0 sockets on my PC are worn and not very good in making reliable contact anymore, especially if a tester is literally "hanging" on them. I sometimes get such errors even without a USB tester. Unfortunately at the moment I have no other way of testing so I can't confirm 100% that it works.

I did a small mod and showed the inside in this video on repairing a power bank ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LSrtbNV9vt4.html (I should really start numbering my videos to make these references easier...) The box is incredibly simple and easy to make and well worth having. I should probably make one for micro USB as well...

@@TheHWcave instead of making another separate USB black box tester with microUSB support, Would it work if you simply connected a microUSB adapter to your existing box? Great vid thanks!

@@SS-pi2yi Yes of course. I do that myself.

The end of the universe as we know it? Good question! I had to test it because I normally use the TC66C (see my videos) for all my USB-C work. The UM34C has no USB-C out (despite the label). On the UM25C, if USB-Cs are swapped, power still gets through and the display shows the voltage but current is shown as 0 despite current flowing. I also noted that regardless whether USB-C in and out are connected correctly or not, the UM25C is sensitive which way around the two USB-C connectors are plugged-in. There is a 50 percent chance the display stays dark and no current flows from source to sink. Flipping either one of the connectors on the UM25C and everything works. It has to be on the UM25C, flipping on either source or sink side makes no difference. When discussing the TC66C , I did a deep dive into USB-C and indeed the connectors / plugs are not truly symmetrically wired. However most devices take care of that, so orientation of the connector normally does not matter. In the UM34C it does matter. Interesting! I did not know this about the UM25C , so I thank you for raising the topic.

@@TheHWcave Thanks for the answer. The reason I asked because I have on of that black X shaped usb tester and I plugged it in reverse to a power bank, frying it.

40 deg C isn't enough to melt plastic or solder. Something else has gone wrong here but it is difficult to understand what you were doing in each case. You are saying that you used the same setup, cables, load, power bank and with one tester it works, and the other one melts? What current were the testers showing (while working)?

@@TheHWcave yes, identical conditions, one tester (simple one) works fine, another tester (makerfire with LCD display) dies within 20 minutes. Maybe 'melt' is an exaggeration but the USB port has a bad smell coming out of it and no longer functions. The tester itself is alive, if I reconnect it to the power bank the display turns on and shows the voltage accurately, but the USB-in does not work anymore. The current is 1.12 amps.

@@Jimmy_The_Goat My only guess is that there was a bad solder joint or contact within the makerfire tester that caused so much of resistance and voltage drop that it overheated. It may be fixable if you open the tester and examine the solder joints (and PCB tracks) around the USB port.

@@TheHWcave And what would I do to fix it?

@@Jimmy_The_Goat Difficult to say without seeing it. Check for anything like solder joints around the connector that look brittle or cracked. Anything that looks different from how the other connectors are. Then go over those with a soldering iron and reflow the solder. See if that fixes it. If the melt happend inside the connector itself you would need a new one but replacing a whole connector is more work than the tester is worth.

you need to adjust your measurement formula to compensate the current draw by the tester itself

@@MohamadHanifAzrai That would be terribly inaccurate, because the tester's current draw fluctuates. You need to either allow power from an external source isolated from the other ports or measure the internal current draw by using a shunt resistor placed at the input.

Sorry to hear that. Yes its a real danger

Sadly I don't have any fnirsi usb testers. If I ever get one, I will test it of course.

No they can't.

Leider nicht aber die Untertitel sind mein original Script und daher sehr detailliert vielleicht geeignet über Verständnisprobleme hinweg zu helfen. Es ist möglich die Untertitel automatisch in Deutsch zu übersetzen. 1. Enable Subtitles. 2. Click Settings. 3 Select Autotranslate 4. Select German

Why? the testers are great. All this video was trying to say is don't use two inputs or two outputs at the same time. This is not something you would normally do but since these testers offer additional alternative connectors to save you hunting for the right converter cable or adaptor, the possibility exists that you can for example plug two inputs into a tester, with the predictable result that something can go wrong. To be fair, the tester probably survives, its more the devices on the other end that may be in trouble when you do this. Just stick with picking one input and one output and nothing will go wrong.

@@TheHWcave , I am trying to find a model that can test the capacity of batteries. Which one would you recommend?

@@jpvoodoo5522 They can all measure battery capacity. To test capacity when charging you need to reset their capacity counters, and then put them in between the battery and charger. To test discharging capacity you need to put them between battery and load. Which model is best depends on the type of USB connection you use (normal, micro or USB-C), but other than that all can do that. One note: If you measuring capacity of a USB power bank from the outside, remember that your are NOT measuring the batteries inside directly but through the DC-to-DC converter in the power bank. That completely messes up capacity figures because a Lithium battery capacity is rated at 3.7V but you are measuring at 5V (after DC-2-DC conversion). So its much better to measure ENERGY (watt hours) not amp hours, because watt hours measurements take the voltage step-up into account. All these 3 USB testers can measure energy as well as amp hours

The point is that it draws 18.5 mA without telling you about it and that means any battery capacity measurement is wrong by that amount. The battery has to power both, the actual load (which the USB stick shows) and the USB stick's own power draw, which it doesn't show. In your weight example, this would be equivalent to a scale that adds 18.5 grams to everything you weigh but doesn't tell you about it.

@@TheHWcave I see what you mean. I assume this is the only situation where USB's power draw matters and should be taken into the account ? But I was, just to clear for all who read, talking about device connected INTO the USB, on the end of it. Because my goal is to measure, for example, how much current the LED light draws, like you did show at 2:11. And in that situation, power draw from USB device doesn't matter.

But what about simply connecting discharged battery to the USB tester.(instead of discharging it and measuring while it discharges) So like this 1(5v power adapter) - 2(USB tester) - 3(battery) and measuring how many mAh is pushed trough the USB tester. In this case the USB tester would not draw power from battery at all. I'm not sure can capacity of a battery even be measured like this, while charging.(don't have much knowledge on this tbh) Using some logic, it should, yes ?

@@kruskotv1311 Yes in that case the power draw of the tester would be covered by the charger. The best option is to use a tester that can be powered externally so it doesn't need to steal power from either end of the USB connection to the thing you want to measure.

Good to hear. The threshold when it stops working depends really on the model of the tester. I also found that when the display shuts down, the processor may still work for and can tolerate even lower voltages. You should however test if the measured values are actually still correct at very low supply voltages. The problem is that the reference voltage for the AD conversion might no longer be correct and cause measurement errors to creep in.