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I have a 5V/10A power supply (with a 2.1mm DC plug) and want to use it to power four or five 5V/2A devices.

But I see that no barrel jacks are rated for 10A (they're all around 5A max - see this Digikey search).

Is this really an issue? I would have thought parts likes jacks, that are basically little more than a metal conductor, would be rated for e.g. a max wattage.

But I see on places like Digikey that instead they're rated for a max voltage and a max current (12V and 5A seem typical values).

It seems odd to have a power supply with a 2.1mm DC plug if you can't actually get a jack that can handle the supply's current. So is it OK to use a 12V/5A rated jack with a 10A power supply as long as the voltage is half the max rated? If it's not OK then what are my options and if it is OK is there anything else I need to watch out for?

I was planning to just twist the wires of my various power cables together and screw them down in a 2.1mm jack-to-screw terminal block. Or solder down a barrel jack on a proto board and then solder each power cable on separately to the same board.

These kinds of setups have always worked out for toying around with typical 5V/2A setups but will there be issues once I start dealing with higher currents?

Parts I'm using:

5V 10A switching power supply Female DC Power adapter - 2.1mm jack to screw terminal block Breadboard-friendly 2.1mm DC barrel jack Perma-Proto Quarter-sized Breadboard PCB DC Plug Cable Assembly 2.5mm http://dn.odroid.com/homebackup/201401132011213194.jpg

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marked as duplicate by Dmitry Grigoryev, Voltage Spike, ThreePhaseEel, Daniel Grillo, Bence Kaulics Nov 17 '16 at 17:40

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ Looks like the weak link here might be the wire gauge, not the connector. \$\endgroup\$ – Wossname Nov 14 '16 at 21:10
  • \$\begingroup\$ I was guessing this would probably fit into the category of questions that make real electrical engineers groan. The answers confirm my suspicion :) Still it's odd that the power supply comes with such a plug when the corresponding jacks don't seem to be typically rated for the supply's current. \$\endgroup\$ – George Hawkins Nov 14 '16 at 21:11
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    \$\begingroup\$ For a connector (or other conductor), over-current causes heating, and over-voltage causes arcing. They are two entirely separate ratings. \$\endgroup\$ – immibis Nov 14 '16 at 22:16
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    \$\begingroup\$ It's fine to plug a power supply that can deliver 10 A into a 5 A jack if you're not actually going to use that much. If you're powering an Arduino (maybe 50-500 mA by itself) or RPi (1-2 A), should be fine. For safe, unattended operation, it's prudent to put a fuse so if somehow your board shorts but doesn't trip the PSU, it won't be dumping 50 W somewhere trying to start a fire. \$\endgroup\$ – Nick T Nov 14 '16 at 23:36
  • \$\begingroup\$ Can you cut the plug off the wire and replace it with a suitable connector/receptacle combo you are able to source? \$\endgroup\$ – nexus_2006 Nov 15 '16 at 0:28
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No, it doesn't work the way you think. At these levels, the voltage and current ratings are independent.

The current rating comes from the contact resistance and the power the actual contact (way smaller than the whole connector) can safely dissipate. This not only includes things like not melting the insulation, but also oxidation and other heat-related degradation over time.

The voltage rating is what the insulation is good for.

Multiplying the voltage and current ratings tells you the maximum power that can be pushed thru the connector. It has nothing to do with what the connector will dissipate. That's soley a function of the current and the contact resistance. In fact, it's exactly the square of the current times the contact resistance.

If you want to use the full output of your 5 V 10 A power supply, you have to use a connector rated to 10 A. It also has to be rated for 5 V, but it would actually be difficult to make a connector that isn't rated to at least 50-100 V, so the voltage spec is not a issue here.

You might ask the manufacturer of the power supply to tell you a specific mating connector it is intended for. Surely they know. Or they know there isn't one, but that consumers aren't going to think of that, and think a 10 A supply is "better" than a 5 A supply. The wire you show looks suspiciously thin for 10 A, at least with reasonable safety and loss.

Basically, your supply is like a 400 horsepower V8 for a Honda Civic. You can't just plug in either one without dealing with other issues.

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  • \$\begingroup\$ Once you get to something like 30A, even thick cables start to get hot and techies may insist screw connectors are fine until one melts with a suitably spetacular result. \$\endgroup\$ – Barleyman Nov 15 '16 at 9:39
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Yes, this is really an issue.

Current rating is mostly based on the power dissipated by the contact resistance.

P = R * i2

So, the heat generated on a connector is about the current, not voltage.

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The voltage and current ratings on connectors are independent. The voltage rating depends on insulation strength, while the current rating depends on contact resistance and construction.

You may be able to use a 5 Amp connector for somewhat higher currents, but it may overheat. I don't recommend it.

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In short, no. Use it to power at most two 5V/2A devices, or split the power supply before feeding it to your devices. Also, careful when using breadboards: the current shouldn't exceed 0.5A there, see the post: How much current can Solderless Breadboards handle?

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To add another perspective, the 2 main tests ran at safety certification labs such as UL are the temperature test and the dielectric test.

The temperature test requirements rely strictly on the current rating; the connectors are loaded with the maximum rated current until they are thermally stable (usually about 4 hours). Temperatures along the connector are measured and checked against their maximum thermal rating. The test voltage is irrelevant and is often any convenient voltage for the test lab to get to the test current; a 50 V connector and 5 V connector may both be ran at 5 V.

The dielectric test is performed at a voltage strictly calculated using the rated voltage of the device. Here, the current rating is irrelevant to the test parameters; a 1 A device will be ran at the same voltage as a 100 A device.

So hopefully this shows that the ratings are independent of each other from a safety perspective.

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