Is there a way to test the current transfer on quick-disconnects & junctions?

Other Hardware General Electronics
1

I recently discovered, by building a little spot-welder for 18650 battery tabs - that my wire, connectors, and soldering can have a big impact on the amount of power that is eventually delivered to wherever I need it to go. If it's not crimped, or if I use cheap wire (DISGUISED as copper cable that is some alloy that looks like copper), and the terminals themselves. I have also discovered, that this fancy oriental disguised wire does the DISAPPEARING trick, and turns itself into a WHITE POWDER not too long after it was purchased as new just a few months earlier.

I can't really get a scientific test by just jumper-cabling my power wires together and shorting them out to visually judge how much spark and smoke I get.

These "anderson powerpole" claim 45 amps, but I seriously do not trust it, since it just does not seem like enough metal contact is actually there to transfer that power. I want to be able to test my quick-disconnects to be sure they can transfer 50, 60, or 100 amps (if possible). So I was wondering if anyone knew or had any ideas, how to test my own battery cables & junctions ?

My first thoughts would be to get a known working load, like a halogen light or something that can draw 50 amps when I test it, then wire it up to my test cable and see if the same 50 amps flows through those cables. Does anyone else have any other suggestions on how to get a reliable test?

2

DocStein99:
I recently discovered, by building a little spot-welder for 18650 battery tabs - that my wire, connectors, and soldering can have a big impact on the amount of power that is eventually delivered to wherever I need it to go.

Yes, that is the case. A wire is just a long thin low-value resistor. A connector has contact resistance as
well (due mainly to oxide layers on the surface of the metal - gold plated connectors are way superior to most
for this reason).

If it's not crimped, or if I use cheap wire (DISGUISED as copper cable that is some alloy that looks like copper), and the terminals themselves. I have also discovered, that this fancy oriental disguised wire does the DISAPPEARING trick, and turns itself into a WHITE POWDER not too long after it was purchased as new just a few months earlier.

CCA wire you mean, copper-coated aluminium. Its a vile thing to be avoided if at all possible. Its certainly
dangeous to use unknowingly in high current circuits as it will cause fires owing to the 3 times higher resistance.
I suspect you've discovered that aluminium corrodes to aluminium hydroxide (white powder).

I can't really get a scientific test by just jumper-cabling my power wires together and shorting them out to visually judge how much spark and smoke I get.

Weigh the cable. Copper is heavy, density 9g/cm^3, aluminium is light, 2.7g/cm^3. Calculate the expected weight of copper for the cross-sectional area you want and check the cable is at least that heavy.

These "anderson powerpole" claim 45 amps, but I seriously do not trust it, since it just does not seem like enough metal contact is actually there to transfer that power.

Anderson connectors are good, yes they can take the current. They come in many sizes upto 350A.

I want to be able to test my quick-disconnects to be sure they can transfer 50, 60, or 100 amps (if possible). So I was wondering if anyone knew or had any ideas, how to test my own battery cables & junctions ?

My first thoughts would be to get a known working load, like a halogen light or something that can draw 50 amps when I test it, then wire it up to my test cable and see if the same 50 amps flows through those cables. Does anyone else have any other suggestions on how to get a reliable test?

You just need to measure the resistance with a 4-terminal measurement. Arrange a reasonable current (several amps, such as your halogen light) to flow down the wire, measure the current and measure the
voltage between each ends of the cable (you can use 2 multimeters or two measurements with one
multimeter, being sure to select the right range each time). Voltage across wire / current = wire resistance.

Then you can calculate the power dissipation of the wire for any current with IxIxR. There are standard
tables of max power per unit length for guages of wire.

3

Also, you can measure the voltage drop across the terminal, if current is known (say, 50 Amps) and the voltage drop across the terminal is 1 volt, that's 50 watts being dissipated just by the terminal. Gets HOT. And the hotter it gets, the more the resistance, thermal runaway.

4

MarkT:
Yes, that is the case. A wire is just a long thin low-value resistor. A connector has contact resistance as
well (due mainly to oxide layers on the surface of the metal - gold plated connectors are way superior to most
for this reason).

I usually buy gold-plated connectors for my small wires, data lines (when possible). I still have to go visit a jeweler to train me on how to identify REAL gold -VS- a possible fake import gold plated contact that could just be some fancy formula dipped tinted paint containing powdered brass. I have never seen gold plated high current terminals, and for what they want to charge me for 8-gauge terminals at $5+ each. At this point, I'd feel more confident electrostatic plate my own terminals with whatever metal I want at whatever thickness.

MarkT:
CCA wire you mean, copper-coated aluminium. Its a vile thing to be avoided if at all possible. Its certainly
dangeous to use unknowingly in high current circuits as it will cause fires owing to the 3 times higher resistance.
I suspect you've discovered that aluminium corrodes to aluminium hydroxide (white powder).

This was my SECOND discovery. The FIRST TIME, at the machine shop - the guy there THREW AWAY a big fat cable, in his Jeep - that ran from battery to his winch. The whole thing was WHITE POWDER - and we couldn't figure out WTF! Winch was 8 months old. This serious problem costed him to call someone else to come rescue when he was stranded and the winch refused to work.

I am going to write the vendor who sold me this cable, a nice friendly note now to explain my frustrations and loss on my project by now having to re-do everything again and re-buy different cable.

MarkT:
Weigh the cable. Copper is heavy, density 9g/cm^3, aluminium is light, 2.7g/cm^3. Calculate the expected weight of copper for the cross-sectional area you want and check the cable is at least that heavy.

Thank you. Hopefully the weight of the insulation that's made from who-knows-what won't interfere too much with the weight of the metal.

MarkT:
Anderson connectors are good, yes they can take the current. They come in many sizes upto 350A.
Anderson Powerpole - Wikipedia

I studied them in fine detail. I ordered "45 amp" terminals, FROM MOUSER (which by the way, is a time consuming task sorting through the 1,000 pages of 10,000 terminals).

I crimp the terminal onto my copper cable. Then test this by trying to pull it apart by hand. Next, my terminals are then soldered to merge the copper wire into the housing. After that, if the round insulation isn't too fat for the square hole - I insert into the shell housing. This worked good for two weeks. Every 2-3 days I disconnect and bring my box on the bench for testing / modification. Now - I got one of the terminals sliding BACK OUT, not making FULL contact. I can already see the terminals are starting to score, gauge, malform. I am not certain exactly how many times these powerpole connectors are rated to be re-connected before needing replaced.

MarkT:
You just need to measure the resistance with a 4-terminal measurement. Arrange a reasonable current (several amps, such as your halogen light) to flow down the wire, measure the current and measure the
voltage between each ends of the cable (you can use 2 multimeters or two measurements with one
multimeter, being sure to select the right range each time). Voltage across wire / current = wire resistance.

Then you can calculate the power dissipation of the wire for any current with IxIxR. There are standard
tables of max power per unit length for guages of wire.

Ok - this is the first time I am learning this nice new test - thank you. So I am taking measurements at the one end, and also again at the other end - correct? As long as the test same at less than 10 amps -vs- 65 amps. My multi-meters will only test up to 10 amps of current.

5

One thing to be aware of is that some connectors are not rated for lots of connect/disconnect cycles, the contact
plating might only be designed for a limited number of operations, and once its worn through corrosion might
be much increased.

4-terminal measurements have separate leads from the "resistor" to the voltmeter - ie the current
doesn't flow through the voltage sensing leads. You need both ends of the cable together to measure its resistance, or very long multimeter leads(!)