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A standard practice in many academic labs, which I'm told is "bad practice", is to use RG58 cables (i.e. standard BNC cables) for power distribution.

Question 1: Why is this considered bad practice?

Question 2: Is there a different sort of cable which is better for power distribution and compatible with BNC connectors?

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    $\begingroup$ 3v, 5v, 12v or 240v? $\endgroup$
    – Solar Mike
    Oct 29, 2019 at 20:52
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    $\begingroup$ @SolarMike 24 V. $\endgroup$
    – Yly
    Oct 30, 2019 at 7:01
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    $\begingroup$ @Yly how much of current. AC or DC power. $\endgroup$
    – user1586
    Oct 31, 2019 at 17:22

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Because it is not a power cable (Q1) using power connectors (Q2).

BNC cable has a solid conductor and a ground braid to electrically shield and mechanically protect the conductor.

Electrical reason: Some ground braids are made of steel, which is not as good a conductor as copper, so voltage losses to the wire would be higher than copper wire. Basically, wasted power.

Edit....

Current creates heat ($I^2 R$ losses). The ampacity rating of a power cable is determined by the maximum temperature the cable's insulation can handle. The BNC wire was never meant to carry power, so the current flowing may cause the insulation to break down and cause a fire.

Safety reason: The main reason BNC cable should not be used to send power is because of the connectors. The outside of the metal BNC connector is uninsulated, so you have a shock risk, if you disconnect the load terminal while power is being applied.

Common sense reason: You may know what you have done so are not at risk, but an unsuspecting person is NOT expecting power on a signal cable.

Even if you found an insulated BNC connector and added a warning sign, if it was disconnected a user may connect a normal connector negating your bad practice.

From: Generic BNC Male Connector UHF Walkie Talkie Antenna 2.8 Inch For Kenwood TK-388

Insulated BNC Connector

No one expects power over a BNC cable. So power distribution over BNC cables is bad practice.

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  • $\begingroup$ There is a variant called high voltage BNC, in which the outer (intended to be earthed) conductor is shaped into a housing which prevents users from touching the central (intended to be live) conductor. $\endgroup$
    – Daniel Hatton
    Nov 6, 2022 at 13:50
  • $\begingroup$ You can definitely run power over a coax. Obvs it all depends on the DC drop you can tolerate, how much power you need, etc. It's a resistor problem basically. In the satellite terminal industry it's pretty common to have one cable that provides DC power (up to 100s of Watts) out to the terminal/antenna, potentially ~100 yards away, along with a reference 10 MHz, and have intermediate band (~2 GHz, etc.) coming back from the terminal, all on the same cable. The question was about BNC connectors, so everything scales to the specifics of the connector involved. $\endgroup$
    – Sonicsmooth
    Sep 26 at 17:27

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