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I've got a 12V powerbank that I would like to use with a 12v device. The power bank output and the device both require 5.5 x 2.1mm male plugs.

I've actually got some random cables and have found two of these exact cables. Now for the weird thing, when I test for continuity with a multimeter, it is different for these cables - so for one cable, I get continuity when I use the two outside surfaces of both the 5.5mm ends. However, on the other cable, I get continuity when I use the outside surface of one end and the inside surface of the other end. Does this not matter for a DC circuit? So if I randomly join together two cables with 5.5mm ends, then I don't need to worry how it is joined or should I make sure the continuity is inside part to inside part and outside with outside?

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  • \$\begingroup\$ Please add description of polarity of the DC plugs at both devices. The polarities they have determine how you should wire the connectors. \$\endgroup\$
    – Justme
    Apr 18, 2020 at 21:32
  • \$\begingroup\$ I'm assuming the polarities are the same as the ends are identical \$\endgroup\$
    – McMath
    Apr 18, 2020 at 21:33
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    \$\begingroup\$ Some devices have positive at center pin, some have negative at the center pin. So please don't assume anything - if you knew you would not be asking here, right? \$\endgroup\$
    – Justme
    Apr 18, 2020 at 21:35
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    \$\begingroup\$ Some equipment with those coaxial power connectors are center positive, and some are center negative (and even AC is possible, I think). You have to look for markings on the equipment to see which polarity (and voltage) it requires (or provides, in the case of power supplies) \$\endgroup\$
    – Peter Bennett
    Apr 18, 2020 at 21:36
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    \$\begingroup\$ A reversed input voltage will probably destroy the device! In order to find out the polarity when there is no label on it you have to reverse engineer the electronics inside. \$\endgroup\$
    – Sim Son
    Apr 18, 2020 at 21:56

1 Answer 1

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Polarity matters in DC. If it is incorrect, either it just won't work, or it will get permanently damaged.

As long as the powered device gets voltage with correct polarity, everything should be fine.

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