DC power supply and true copper wires - beware they need maintenance

[Kiriakos GR]

At my KENWOOD DC bench power supply 0~35V 10A, I am using a pair of 1.5m long extension cables.
These are Hirschmann cables 1,5mm of true copper and flexible.
(These are a close equivalent to Staubli top tear copper wire for test leads.)

Long story in sort, I did install fresh banana plugs in both ends, at the year 2010.
And they were working with rock solid performance, but after a period of ten years, they started to develop an issue.
It started to be developed voltage drop under load.
DC load it can be as small as 50mA or 10A, in both situations an measurable voltage drop was there.

The smoking gun, this was not the age of the cable, but formed oxidation this caused due atmospheric air, from the connection with the banana plug plus three centimeter inside the actual wire.

The fix, I did remove three centimeter of wire at all four ends, and I even replaced all the banana plugs with top tear Staubli.
The results are amazing !!

I got recently a pair of new lithium polymer 10.000 mAh its one, and I gave them it first charge at the precise voltage of 4.2V
At my PSU cables, and after this maintenance, the actual resistance of these 1.5mm Hirschmann, this is now looks as invisible. 

Originally and prior getting understanding of what was the actual problem, I thought to use the function of Sense wires, this available at my KENWOOD DC bench power supply.
But I did run in to another problem, the PSU this is old technology, Sense function this could track down differences of 0.5V up to 1.5V
In other worlds, there was no enough sensitivity, for my specific application, in which I need mV level of precision.

My message to anyone thinking to get a modern DC PSU, with Sense leads support, you better inspect first actual sensing sensitivity prior making a choice.   

[Andrew-88]

A 1.5mm² conductor has a carrying capacity of approximately 16-20A.
And therefore, this cannot be stressed due the amperage of your PSU.

Its in the nature of stranded wire to get in touch with oxygen, strands they leave space for oxygen to penetrate.
The sign of oxidation = turning to green or black color, this is a proof that this is pure copper 99% and not any cheap alloy. 

I bet that at your repairs workshop, you do not have any humidity issues.
At problematic work spaces, such issues arise much sooner at bolted wires.
Soldered wires they are less prone to oxidation, but not immortal.   
 

[Kiriakos GR]

I had in stock four Gold plated MC banana plugs, soldered type.
The ones that I did remove, these were bolted.

This Hirschmann cables, they come to me as test leads wires, when I got my analog Gossen Metrawatt MA4S from Germany.
I am totally unaware of their manufacturing date.
But they do have inside an second sleeve, this is a white wear indicator.

Lesson learned, if I ever decide to replace them, I will buy 50cm longer cables than of what I actually need. 

Several years ago, I did try twice to invite Hirschmann at ITTSB.
They are owned by a bigger corporate umbrella, and they are unable to make any decisions of their own.