Hello. What cross-section has the cable from the twisted pair from the Internet? And what is the maximum current that can flow through it? I will add that it is difficult to remove the insulation squeegee because it also tears the cord (the squeegee has a minimum clamping value of 0.2mm2).

The diameter measured by callipers - 0.45 mm

Write whether it is pure curiosity or do you really want to use it and for which installation?

I would like to use it to connect the rear reversing and fog lights. Light bulbs are one 21W and two 4W each. At the same time, this 21W or the two at 4 w can be lit, so the total load is 8W. Voltage 12V, or current at 21W is 1.75A, and at 8W 0.67A. Can it be done or not? It is worth noting that these lights are not constantly lit, and these wires from the twisted pair are about 7cm long, the rest of the installation is made by a factory-made cable, which is a bit thicker.

The diameter of the duct is not everything. In such applications, insulation must be adapted to the atmospheric conditions.

Why do you want to use the twisted pair wire instead of the same cross-section of the wires that already exist in the original wiring installation and should be soldered and this should do the trick.

In the current PoE standard, the power pair carries 350 mA of current (15.4W at 44V). Considering that the current flows only one way because I assume that the return is through the mass of the vehicle, 8 wires give you the ability to send 2.8A without overloading the cable.

Dear author, saving has its limits

I have a cable in the twisted pair and not a wire. It can not be used to directly solder wires because it would be uncomfortable. The plates are made of aluminum and you have to get a little tired to solder it.

And the twisted pair which technique will you connect with the installation?

Cross-Section & Maximum Current Capacity of Internet Twisted-Pair Cable: Insulation Removal Issues

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#1 16761141 16 Oct 2017 20:00

smartfon smartfon

Level 4

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Post #1
16761141 16 Oct 2017 20:00

Hello. What cross-section has the cable from the twisted pair from the Internet? And what is the maximum current that can flow through it? I will add that it is difficult to remove the insulation squeegee because it also tears the cord (the squeegee has a minimum clamping value of 0.2mm2).
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#2 16761168 16 Oct 2017 20:08

1repcaK 1repcaK

Level 21

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Post #2
16761168 16 Oct 2017 20:08

The diameter measured by callipers - 0.45 mm
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#3 16761173 16 Oct 2017 20:10

Foxtrott Foxtrott

Level 34

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Post #3
16761173 16 Oct 2017 20:10

Core diameter = 0.511 mm
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#4 16761183 16 Oct 2017 20:12

marqqv marqqv

Level 32

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Post #4
16761183 16 Oct 2017 20:12

Write whether it is pure curiosity or do you really want to use it and for which installation?
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#5 16761200 16 Oct 2017 20:16

smartfon smartfon

Level 4

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Post #5
16761200 16 Oct 2017 20:16

I would like to use it to connect the rear reversing and fog lights. Light bulbs are one 21W and two 4W each. At the same time, this 21W or the two at 4 w can be lit, so the total load is 8W. Voltage 12V, or current at 21W is 1.75A, and at 8W 0.67A. Can it be done or not? It is worth noting that these lights are not constantly lit, and these wires from the twisted pair are about 7cm long, the rest of the installation is made by a factory-made cable, which is a bit thicker.
#6 16761209 16 Oct 2017 20:19

beatom beatom

Level 38

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Post #6
16761209 16 Oct 2017 20:19

The diameter of the duct is not everything. In such applications, insulation must be adapted to the atmospheric conditions.
#7 16761229 16 Oct 2017 20:25

marqqv marqqv

Level 32

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Post #7
16761229 16 Oct 2017 20:25

Why do you want to use the twisted pair wire instead of the same cross-section of the wires that already exist in the original wiring installation and should be soldered and this should do the trick.
#8 16761238 16 Oct 2017 20:27

sanfran sanfran

Network and Internet specialist

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Post #8
16761238 16 Oct 2017 20:27

In the current PoE standard, the power pair carries 350 mA of current (15.4W at 44V).
Considering that the current flows only one way because I assume that the return is through the mass of the vehicle, 8 wires give you the ability to send 2.8A without overloading the cable.
#9 16761247 16 Oct 2017 20:29

technikabasenowa technikabasenowa

Level 33

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Post #9
16761247 16 Oct 2017 20:29

Dear author, saving has its limits
#10 16761248 16 Oct 2017 20:29

smartfon smartfon

Level 4

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Post #10
16761248 16 Oct 2017 20:29

I have a cable in the twisted pair and not a wire. It can not be used to directly solder wires because it would be uncomfortable. The plates are made of aluminum and you have to get a little tired to solder it.
#11 16761260 16 Oct 2017 20:32

marqqv marqqv

Level 32

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Post #11
16761260 16 Oct 2017 20:32

And the twisted pair which technique will you connect with the installation?
#12 16761262 16 Oct 2017 20:32

smartfon smartfon

Level 4

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Post #12
16761262 16 Oct 2017 20:32

2.8A for 8 zlotys, or 0.35A for a single vein? Is 2.8A per single vein?
#13 16761267 16 Oct 2017 20:33

technikabasenowa technikabasenowa

Level 33

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Post #13
16761267 16 Oct 2017 20:33

Colleagues about what to debate here

I think it's only when the new subject is going to be out of light
#14 16761281 16 Oct 2017 20:35

karolark karolark

Level 42

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Post #14
16761281 16 Oct 2017 20:35

smartfon wrote:
2.8A for 8 zlotys, or 0.35A for a single vein? Is 2.8A per single vein?

Is not it better to make clips?
The author do not go this way, do not go
#15 16761282 16 Oct 2017 20:35

smartfon smartfon

Level 4

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Post #15
16761282 16 Oct 2017 20:35

Let the great gentleman write what wire would be the most suitable for such installation? 0.75mm2?
#16 16761297 16 Oct 2017 20:38

karolark karolark

Level 42

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Post #16
16761297 16 Oct 2017 20:38

The answer is resist mechanical strength and good insulation
twisted pairing is not suitable for this
And the topic to the basket
#17 16761312 16 Oct 2017 20:45

smartfon smartfon

Level 4

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Post #17
16761312 16 Oct 2017 20:45

https://www.elektryzuj.com.pl/pl/p/PRZEWOD-SA...MI1sbpqOb11gIVysqyCh0UKwf1EAQYASABEgJS4_D_BwE Such something will work?
#18 16761479 16 Oct 2017 21:27

radsat radsat

Moderator

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Post #18
16761479 16 Oct 2017 21:27

3.1.17. Do not send very basic questions that can be found in the user manual or generally available sources. Do not present the attitude that I am due. Take care of the level of questions and discussions. Thank you.
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Topic summary

✨ The discussion revolves around the cross-section and maximum current capacity of twisted-pair cables used for internet connections. Users provide varying measurements for the core diameter, ranging from 0.45 mm to 0.511 mm. The author seeks to utilize the twisted pair for connecting rear reversing and fog lights, with a total load of 8W at 12V, which translates to a maximum current of 0.67A. Concerns are raised about the suitability of twisted pair cables for this application, with suggestions to use thicker, factory-made cables instead. The PoE standard is referenced, indicating that a power pair can carry up to 2.8A without overloading. The author expresses difficulty in removing insulation without damaging the cable, and alternative wiring solutions are discussed, including the use of clips and other types of cables.

FAQ

TL;DR: A single CAT5/UTP conductor typically handles 350 mA; “the power pair carries 350 mA of current.” Use automotive‑grade wire for car lights. [Elektroda, sanfran, post #16761238] Why it matters: This helps DIYers decide if Ethernet cable can safely power 12 V lamps and what to use instead.

Quick-Facts

Single UTP solid conductor diameter measured: 0.45 mm (approx. 0.16 mm²). [Elektroda, 1repcaK, post #16761168]
Alternate measured core diameter: 0.511 mm (approx. 0.205 mm²). [Elektroda, Foxtrott, post #16761173]
Reference load: 350 mA per powered pair in PoE context; don’t equate to automotive. [Elektroda, sanfran, post #16761238]
Automotive wiring must tolerate weather, oils, and temperature swings; pick suitable insulation. [Elektroda, beatom, post #16761209]
Best practice: match OEM wire size and join like‑for‑like with proper technique. [Elektroda, marqqv, post #16761229]

Quick Facts

What cross‑section does a typical Ethernet twisted‑pair conductor have?

Using the posted 0.45 mm diameter, the area is about 0.16 mm² (A = π·r²). Treat this as an approximate value only. [Elektroda, 1repcaK, post #16761168]

How much current can one UTP conductor carry as a rough reference?

A commonly cited reference from PoE is 350 mA per powered pair path. This is a telecom context and not automotive. “The power pair carries 350 mA of current.” [Elektroda, sanfran, post #16761238]

Can I parallel multiple CAT5 conductors to reach around 1.75 A for a 21 W bulb?

Eight conductors at 0.35 A each imply 2.8 A total in that telecom example. Paralleling lowers resistance, but automotive conditions differ, so use proper automotive wire. [Elektroda, sanfran, post #16761238]

Is twisted‑pair cable suitable for exterior automotive lights?

No. It lacks the mechanical strength and insulation robustness vehicle harnesses require. “Twisted pairing is not suitable for this.” [Elektroda, karolark, post #16761297]

What wire should I use instead of Ethernet cable for car lights?

Match the existing harness cross‑section and use automotive‑grade insulation. Join like‑for‑like and make a quality soldered or crimped connection. [Elektroda, marqqv, post #16761229]

Why is stripping CAT5 conductors so difficult with a 0.2 mm² stripper?

The conductors are thin, and many strippers don’t adjust precisely at that size. The OP noted the insulation tears with small tools. Use a precision adjustable or thermal stripper. [Elektroda, smartfon, post #16761141]

Will 7 cm CAT5 pigtails overheat at 1.75 A?

The OP’s pigtails are about 7 cm. Short lengths reduce voltage drop, but heating risk remains if insulation and routing are poor. Prefer automotive wire. [Elektroda, smartfon, post #16761200]

Can I use the vehicle chassis as the return path for these lamps?

Yes, many circuits use chassis ground. The cited reply assumed return through vehicle mass; ensure clean grounds and corrosion protection. [Elektroda, sanfran, post #16761238]

How much current do my bulbs draw at 12 V?

From the OP: 21 W draws about 1.75 A, and 8 W draws about 0.67 A. Size wiring and protection to the highest expected current. [Elektroda, smartfon, post #16761200]

What’s the real risk of using Ethernet cable in a car even if it “works”?

Insulation not designed for oils, moisture, and temperature cycles can degrade and fail, causing shorts or intermittent faults. Choose automotive‑rated insulation. [Elektroda, beatom, post #16761209]

I must connect to aluminum parts—should I solder?

The OP notes aluminum is hard to solder. Prefer crimp lugs or mechanical fasteners with proper anti‑corrosion measures instead of ad‑hoc soldering. [Elektroda, smartfon, post #16761248]

What is CAN bus in cars?

CAN bus is a robust in‑vehicle network protocol that lets ECUs communicate over a shared two‑wire differential pair. [Wikipedia, 2024]