Hi, I was wondering how many amps at 5V can an audio enameled cable support. I say audio because they are the typical cables you see in headphones:



For those not familiar with them, these wires are made of a bunch of really thin copper wires that are coated individually in insulating paint (enamel), then twisted together to create one color. They are useful because in just one sleeve you can fit as much of them as you want, and since the paint is insulating, they can carry different signals.

My guess is they work fantastic for low voltages and of course low amps. Now that's the data I want to know.

1. There must be some voltage limit (may be 10V?) at which the cables inside the sleeve starts short circuiting because of the high voltage.

2. Also, there must be an amperage limit at a "safe"... say 5V voltage (may be 3A?) at which the heat starts to heat the cable so much it damages its insulating paint, ending in a short circuit again.

I am asking first because I am curious about this information, and second because I just replaced a connection between a 3.7V battery (4.2V peak) leg and the direct soldered PCB pad by about 2 inches (5 cm) of two colors of these enameled cables (2 colors, same path, just to make the cable thicker). I used this enameled cable becase the space is really tiny and there's no other way, path must be slim, thin, and flexible, and only these cables fit.

I want to check in my real example, knowing the length of the cable (2 inches, 5 cm) and it's total diameter (2 cables of diameter 0.1mm), where are the limits.

 

ampacity of conductor is largely determined by conductor size (area of cross section) and allowed temperature.
there are other factors too but they are less important. google "ampacity table" that convers size you have. usually continuous duty is considered but depending on application duty cycle or time circuit is under high load can be important and - potentially major factor.

other factors also exist but in general maximum operating voltage is determined by quality of insulation. better insulation can withstand larger voltage.

voltage drop is result of wire resistance so length also must be taken into account. 4V loss is not a problem in 220V circuit but certainly is in 5V circuit.

 

The resistance wll be determined by the size and number of conductors and as the wire I have seen is so very thin it may be difficult to measure accurately. Soit will be useful to measure the resistance of an existing cable. That will require an accurate ohm meter set up to read values of under ten ohms. The accurate process is to have a regulated curret source pass 100 milliamps through the cable and then read the voltage drop accurately with good resolution. There will be one millivolt per milli-ohm resistance. So the resistance can be found with reasonable accuracy.

 

Check the mfg. data or for a similar if unable.

 

The caution with using this kind of wire for power is that it is subject to catastrophic short circuit failures from the varnish insulation wearing through if the cable is flexed a lot.
And I doubt that the current capacity will be very much, because of the higher voltage drop.

 

Check the mfg. data or for a similar if unable.

Yeah, the thing is I want to do it myself to get an idea of its properties. Only thing I've found is it's rated at 30V.

 

Here is what I did:


I am sorry for mixing cm and inches, I think I should just stick to cm...
Original on the left, battery leg soldered to the PCB pad.
My fix on the right, the pad is broken, so I have to connect the battery leg with a cable to the other side. Since the space is very small, I am forced to use a very thin super flexible cable capable of doing a 180º turn due to structure. These enameled cables work perfect mechanically for the job, but I was wondering how well they perform for this task compared to the ones inside, for example, a USB cable known to be able to charge a phone at 30W, for example. I decided to use 2 cables so the total resistance of the path is less, but since I don't know the specs of these cables, may be 2 cables is overkill, who knows. The length of the cable path is about 5 cm and the cables have a diameter of 0.35 mm each, which makes a circular area of 0.38 mm^2, x2 cables, making a total of 0.76 mm^2. However, that area includes air inside the circle, the enamel and also some cotton strength braid, besides the copper cores/threads. With this information I don't know how to determine the max amp / voltage supported.