UM25C & LD25 USB + Cable tester review by Texas_Ace - I figured out why my LII-402 was not working!

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Texas_Ace
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UM25C & LD25 USB + Cable tester review by Texas_Ace - I figured out why my LII-402 was not working!

Ok, I have reviewed a few RD tech products in the past and have been happy and very impressed with all of them.

About a year ago I reviewed the old USB tester and load tester that they offered and they worked quite well at testing USB power ports and to see if USB devices were working or charging like they should.

I have used it far more then I would of guessed since I got it.

They recently released a new version of both the USB tester and Load tester. When they first approached me about reviewing it I was skeptical as I was not sure what you could really improve.

The big selling point seemed to be a Bluetooth app to watch the meter on your phone, which I saw as more of a niche use case.

The I saw the real improvement, the new versions had Micro-USB and USC Type-C input ports!

At first that does not sound like much but this now allows you to test your USB cables to make sure they are not the problem. In addition to being able to use the tester with a cable plugged in instead of being tied to a USB port at odd angles.

I actually had the perfect item I wanted to test this on so I told them to send me a sample for review. Took me longer then I want to admit to get around to it but I finally did.

So I have had 2 of the LII-402 chargers for some time but they would only ever charge 3 cells at a time. I had always thought that the cables could be the problem but when I tried what I thought were better cables it did not fix the problem.

Now I can find out for sure!

At first glance both the USB tester and Load tester are larger then the older versions but also a lot more features. The load tester by itself also now shows voltage for example.

And the USB tester has a much larger and earier to read screen:

So first I set about playing with the features and basic testing, such as the mah counter that shows how much power your device has used:

The voltage graph:

and menu (I recommend upping the screen timeout):

So now to start testing, First I plugged in the charger with some drained cells to the tester and decided to see what happens.

It would gladly pull 1A but anytime I tried to start more then 2 cells charging it would stop them and just would not go above 1A.

So now to test the Cable, I unplugged the charger and plugged the cable into the load tester to get an idea of what was going on, at 1A it was only getting 4.6V to the load tester:

At 2A it was at 4V (now it was lower then normal since there were 2 cables but the outcome is the same)

Thus this seemed to confirm my idea that the cable was the issue. So I tried my known good cable with the charger and sure enough, it worked perfectly!

Then I got down to the technical testing. I connected the tester directly to the USB power adapter and took a baseline voltage reading by holding the next button on the following screen with 1A of current being pulled through it. This records the input voltage from the power adapter at this current.

After that I disconnected the tester and then plugged in the cable in question to the same power adapter (so the input voltage would be the same) and to the tester input and turned the 1A load back on. I then held the next button again so it can run the calculation and here is the result:

No wounder it was shutting down with more then 3 cells charging, it was only seeing at most 4.1V! The stock cable with the LII-402 has a whopping 762mohm’s of resistance.

To put them in perspective my good cables had around ~150-200ohms with most in the 300-500ohm range.

I then set about testing all the other cables I had, finding that you really can not judge a book by it’s cover. Some I was sure would suck were not bad and some I thought were good were bad.

I ended up just connecting the cables to a 1A load and seeing what the voltage was, anything over 4.5v passed as usable. Anything over 4.75v was good. I had 2 that were over 4.9v that are very good.

Overall well worth the time and money IMHO to finally be able to scientifically sort all my cables and figure out which ones to keep and which to toss aside.

I did not try the Android app myself as I don’t install random apps unless I can’t help it but I looked it up and it looks nice. Good for watching things from afar.

RD Techs official store is located here: https://rdtech.aliexpress.com/store/923042

I also use 2 of their power supplies almost daily as well. Only issue I have had is I used one of them so much I wore through the plastic cover on the power button lol.

Edited by: Texas_Ace on 07/14/2018 - 10:05
MRsDNF
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Thanks TA. Nice detective work. Beer

My current and or voltage measurements are only relevent to anything that I measure.

Budget light hobby proudly sponsored by my Mastercard and unknowingly paid for by a hard working wife. 

djozz said "it came with chinese lettering that is chinese to me".

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

Old-Lumens. Highly admired and cherished member of Budget Light Forum. 11.5.2011 - 20.12.16. RIP.

 

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So you’re saying I need to ship you all my usb cords ?

OK

καὶ τὸ φῶς ἐν τῇ σκοτίᾳ φαίνει καὶ ἡ σκοτία αὐτὸ οὐ κατέλαβεν

BlueSwordM
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Hmm.

I would recommend you Ugreen and Blitzwolf cables if you want some low resistance ones.

Also, its mOhms, not Ohms. Otherwise, you would be seeing 4,5V at 1A, but more like 0,5V.

d_t_a
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Dodge Reviews (member dodge_911 here) has been doing lots of micro-USB cable reviews using USB testers in his Youtube video channel. May also be worth making some cable comparisons..

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That was very good troubleshooting there .  I ordered an LD35 from them and will put it to good use now.

Texas_Ace
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Boaz wrote:
So you’re saying I need to ship you all my usb cords ?

OK

lol, once you get in the groove it moves fairly quickly. I actually found a box with about twice as many cables as the picture and sorted through them all.

I think I ended up with about 30% that were basically unusable (backed up by many of those giving me issues in the past), 30% were passable for basic small things and the rest were split between good cables and better cables.

Texas_Ace
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BlueSwordM wrote:
Hmm.

I would recommend you Ugreen and Blitzwolf cables if you want some low resistance ones.

Also, its mOhms, not Ohms. Otherwise, you would be seeing 4,5V at 1A, but more like 0,5V.

Yep, I have some Ugreen cables and they tested very well. I will be spending the extra for good cables from now on.

You are also correct on the ohms, not sure why I didn’t catch that.

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Interesting, a lot more expensive but nice to know and it is built for the task.

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Say, speaking about UGreen.

I just found out they carry 20AWG and 18AWG USB-C cables.

Probably the THICKEST USB cables on the planet.

You should probably buy one of them, just to make sure you get the absolute lowest resistance.

Here is the 18AWG USB-A to USB-C:

https://www.aliexpress.com/store/product/Ugreen-5A-Nylon-Type-C-Cable-Fa...

20AWG USB-C to USB-C:

https://www.aliexpress.com/store/product/Ugreen-3A-USB-C-to-Type-C-Cable...

A bit expensive for a cable, but it is worth it.

Texas_Ace
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Interesting and that price is actually not that bad at all, I expected much higher.

I would get one if I had any USB-C devices that needed a cable.

I still use a galaxy S5 myself and most of my other hardware is equally aged or worse lol.

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Yeah.

The highest AWG cable I could find that is in the micro-USB category was by Anker with 20AWG power wires.

Still, 18AWG on a USB cable is mind boggling to say the least. Would be extremely good to test USB powerbanks and see if the manufacturer is padding the numbers, and not having to worry about a cable losing a ton of energy to heat.

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BlueSwordM
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I was speaking of USB-C.

Doing 18AWG, while quite hard on micro-USB, it is doable.

Using the same diameter wire is harder with USB-C since it has extra pins for reversibility and more pins.

angerdan
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Here’s a video about how to check cable quality on the UM25©:

UM25© Measure Type-C and Micro cable resistance same with UM24© and UM34©)

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Thanks for posting this! I just got a new phone and been researching USB type C. Studying up on chargers and cables is a must. If you go cheap or buy the wrong cable or charger you could easily brick you phone.

USB type C can pump some serious wattage!

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I’ve been testing a lot of my USB cables last night… most of them came from the factory with various USB devices that I bought.
Just about all of them seem to have fairly high resistance, aside from a Blitzwolf USB C cable I paid good money for and a 6-inch Cable Creations one – that one has low IR primarily because it’s so short.

I try to order shorter USB cables these days, to help keep IR low. I just ordered a micro USB 1.5 ft UGreen one plus another 1.5 ft one from Monoprice – I’ve seen some positive comments about them. Let’s see.

Texas_Ace
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I also ordered a Ugreen cable recently and it tested good as well, although I have not actually put it into use yet, waiting for my current cable to wear out first lol.

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Texas_Ace wrote:
I also ordered a Ugreen cable recently and it tested good as well,.
Which one did you get?

I ordered this one: http://a.co/d/iEW95ii

Texas_Ace
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I don’t remember, it was a few months back, about when I did this review. It was on sale at amazon so I picked it up.

I think that ugreen generally has pretty good quality though.

BlueSwordM
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@Pete7874, you are using the Drok USB load+meter combo, right? I forgot to tell you something about the method I told you about yesterday.

The method I showed you earlier does not take into account the power supply voltage dropping under load.

That means to compare cables, it is very accurate of course, and reliable within that data set.

HOWEVER, to actually measure the resistance of a singular cable, it is not reliable at all, since the power supply drops voltage under load.

You need a USB meter like the UM25C to calculate a single cable’s resistance.

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BlueSwordM wrote:
The method I showed you earlier does not take into account the power supply voltage dropping under load.
The power supply I’m using has a voltage display, and I can see it dropping slightly under load. For example, at idle it’s at 5.26V. At 1A it’s at 5.24V. So, could I use this information in conjuction with voltage data from the DROK load tester to more accurately calculate cable resistance?

Quote:
You need a USB meter like the UM25C to calculate a single cable’s resistance.
I ordered one.
BlueSwordM
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Yes, but you need a power supply that supports QC 3.0 or one without voltage cable compensation.

I’ve tested it today on my dual USB power supply featuring QC 3.0 and USB-A 2.4A, and the USB 2.4A was compensating for the voltage drop, to the point the voltage under load was higher in some instances than the idle voltage.

Testing using the QC 3.0 port netted much more accurate and reliable results.

TLDR: Find a USB port that doesn’t do voltage compensation. Techs like SmartID/VoltageBoost do this.

Edit: Looks like your USB supply does do voltage compensation. Find one that has QC 3.0, which doesn’t do cable compensation unless the protocol is activated.

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Thanks. I don’t have any qc3.0 power supplies. Will this still be required even if I get the UM25C?

BlueSwordM
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Yeah.

If you only want to compare cables, it’s perfectly fine.

If you want to measure cable resistance, then it’s not too good.

However, the UM25C can do many things other than testing cables of course.

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BlueSwordM wrote:
However, the UM25C can do many things other than testing cables of course.

Indeed it can, I am surprised how often I pull it out to troubleshoot charging or other issues with random devices. Really speeds up the process.

Although the cable testing is the feature that really makes this model stand out from other options and past models. So that is why I focused on that.

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I have a USB C power supply that came with my Pixel2 phone that can output 9V, but I don’t believe it is technically QC3.0. I think Google uses some other coding scheme. The HD35 probably will not be able to trigger it.

BlueSwordM
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Yeah. The Pixel line of phones uses USB-C PD.

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On the topic on USB cables, I recently got the USB-C cable from UGreen, which I found out uses 18AWG power wires.

And I can confirm. This cable is extremely impressive. The resistance of the cable is actually extremely low, at 0,30Ohms, or 30mOhm!

It’s very impressive. It’s actually the first cable that I’ve got that can outperform my current power supply at a max current of 3,4A before the voltage collapses on the power supply itself!

Voltage under load with the power supply

Voltage under load with the cable

By doing (Vload-Vload cable) / Iaverage = R = (5,090V-5,060V)/1,0035A = 0,0299 Ohms

We find that the cable’s resistance is 0,03Ohm, or 30mOhms as stated before. This is for the 0,50m cable BTW. The 1,00m cable would be 0,060Ohm, which still are the lowest resistance cables that I’ve EVER FOUND.

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BlueSwordM wrote:
Find one that has QC 3.0, which doesn’t do cable compensation unless the protocol is activated.
So, how would I verify if a particular QC3.0 power supply doesn’t do voltage compensation?

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