RD 25A Cable Set

Of course, cables like these are often better and cheaper to make yourself, but in this case I just couldn't resist the sale prices and ordered two sets right away :) In any case, I think the information will be useful.

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Hobbyists, and others too, usually use cables like these in more than one set; often they need quite a few. That's partly why I ordered these to go with the ones shown earlier. In this review, I'll compare them to see why these cost 2-3 times as much.

As always, the packaging is in RuiDeng style: a foam box. Damn, cables in a foam box! I got an open-frame power supply today in nothing but an envelope, while these are cables that are pretty much impossible to damage, yet they put them in a box. Still, it's nice :)


The product page offers two options, X15 and X25, which differ in their maximum continuous current. The cable cross-sections differ accordingly. Also, the plugs on the 25A version have some kind of yellow coating.


Besides the bag, the set includes two power cables, a signal cable, and a little sheet of paper.


The USB-A to MicroUSB cable is as basic as they come: no silicone insulation, no reinforcement, just a plain cable. I didn't even unwind it to measure its length.


Now let's take a closer look at the set of power cables.


Just in case, here are the dimensions of the alligator clips and banana plugs, though I doubt anyone cares. The most useful measurement here is the maximum opening of the alligator clip.


1. The alligator clips can be disassembled (more or less), while the banana plugs are molded as one piece.
2. The cable is marked with its cross-section and maximum temperature. That temperature isn't so important for the cable itself, but when you're working with a soldering iron on your bench, it's very important indeed.
3, 4. For comparison, here's the cable from the previous review. The alligator clips are exactly the same, but the banana plugs are completely different. To be honest, RuiDeng's banana plugs are worse; I'll explain why later.


The thing is, on the banana plugs of the cables under review, the connection is made through a spring-loaded section, and the contact often gets worse over time. I know users often just solder this spring to the plug itself, but that's inconvenient.


The previous cables have a single spring that sticks out at the side and presses the plug body against the socket, so there's no spring acting as an “intermediary.”


Also, the X25 (and X15) has a side hole for connecting additional cables, while the older version has it on the same axis as the plug. Of course, different setups call for different things, but the second option is more convenient when working with power supplies from RuiDeng, for example, because a plug inserted into the side often blocks some of the control buttons.


The stated cross-section is 2.51 mm², and the wires are just over a meter long, including the plug and alligator clip. So I connected the cables in series and applied a current of 5 A. This gives us a more convenient voltage drop to calculate, as if we were measuring at 10 A over a length of one meter.

The voltage drop came to 76 mV, equivalent to 10 A over one meter. That puts the resistance at around 7.6 mΩ per meter of cable.
According to the tables, copper wire with a cross-section of 2.5 mm² should have a resistance of 7.41-8.05 Ω, so in my view, everything is right on spec.

The remaining tests were conducted at a current of 24 A.


I ran them at 24 A for a while. The cable warmed up to about 35-40 degrees, after which I shifted the thermal camera's focus to the power supply's output terminals. The terminals are what I’m most concerned about. The cable is just a piece of metal—what could happen to it? But the connector is a mechanical part, subject to wear, heating, and so on.
Even after warming it up, the terminal temperature was about 45 degrees. That’s perfectly normal for new plugs, but we’ll see how they hold up over time. I recommend keeping an eye on the terminal temperature.


Here’s the same current, but after the cable had warmed up. You can see that the voltage has risen. This is because copper has a positive temperature coefficient of resistance; incidentally, resistance is usually specified at a temperature of 20 degrees.
I once saw a YouTube video where someone used copper wire as a measurement shunt. I can tell you, that’s a very bad idea.



Conclusions.
Overall, these are decent cables, but there are a few little things I liked better about the previous cables—specifically, the type of spring on the plug and the way the extra cable connects. The latter is very much a matter of personal preference, but when it comes to the spring, I’m still leaning away from Riden cables. On the plus side, the wires have soft silicone insulation and a genuine cross-section.

That’s all for today. I hope you found this useful, and I look forward to your comments.