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For a Power-over-Ethernet type of project, I'd like to use cables with low resistance.

It seems a higher category (CAT5, CAT6, CAT7) does not necessarily mean the conductors used are larger in diameter as well.

Any hints on how to identify the ethernet cables with largest conductor diameter / least resistance?

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It seems a higher category (CAT5, CAT6, CAT7) does not necessarily mean the conductors used are larger in diameter as well.

Speed is the most important issue here and making the conductors thinner means that the capacitance between conductors is smaller and hence there is a greater likelihood that data can be transmitted at higher speeds. This runs counter to your requirement for bigger conductors and probably takes precedence.

Any hints on how to identify the ethernet cables with largest conductor diameter / least resistance?

My 1st advice is to send power at a higher voltage level so that the \$I^2 R\$ losses are smaller AND, use an appropriate buck converter at the receiving end of the power. My 2nd advice is to use multiple parallel cores for transmission of power thus \$I^2 R\$ losses are reduced. But, be careful about using data lines with a noisy switching converter.

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  • \$\begingroup\$ Bigger wire also means less resistive loss. From a quick net search, Cat 5 is typically AWG 24 while Cat 6 is typically AWG 23, so Cat 6 does ("typically") use larger wire than Cat 5. Cat 7 is apparently often AWG 23, so no further improvement there. \$\endgroup\$
    – The Photon
    Mar 31, 2020 at 16:30
  • \$\begingroup\$ Maybe CAT 6 wire spacing is a tad more than CAT 5? \$\endgroup\$
    – Andy aka
    Mar 31, 2020 at 16:32
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    \$\begingroup\$ It's also possible to buy special heavy gauge cable for PoE. \$\endgroup\$
    – The Photon
    Mar 31, 2020 at 16:34
  • \$\begingroup\$ Has it got the same data throughput I wonder? \$\endgroup\$
    – Andy aka
    Mar 31, 2020 at 16:38
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    \$\begingroup\$ @user3002097 I can't explain why boosting then bucking caused the excessive current draw. Not without schematics anyway. Maybe start a new questions and post the schematics to get answer. Please leave me a link if you do. \$\endgroup\$
    – Andy aka
    Apr 1, 2020 at 10:12

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