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I have a device (PC fan) which wants 2.0 amps, and a DC adapter that supplies 1.8 amps; both 12v. As I understand it, using this adapter will cause overheating and reduced voltage.

My probably-foolish theory is that I can cool the adapter (I'm customizing a refrigerator for homebrewing) to make up difference, and prevent either device from failing.

Assuming I keep it safe and dry, what are the effects I should expect from cooling the adapter to ~15ºC? Will the voltage hold at, or move closer to 12? Will either device be damaged?

...is my initial assumption even accurate?

Thanks in advance!

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    \$\begingroup\$ "As I understand it, using this adapter will cause overheating and reduced voltage." Unless it exhibits one of the other half-dozen behaviors that an underpowered supply has... \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Jul 20, 2017 at 23:58
  • \$\begingroup\$ The ratings of 1.8 A and 2.0 A (for the fan) are likely within manufacturing guard-band specifications. Why you don't just try them together, plane and simple, maybe do some measurements, try the DC adapter to the touch before bothering yourself with over-sophistication of cooling? \$\endgroup\$
    – Ale..chenski
    Commented Jul 21, 2017 at 0:42
  • \$\begingroup\$ Fold-back, fusible failure, FET degeneration over time, FET degeneration in short time, Diode degeneration, Capacitor Failure through high ripple currents (primary or secondary), unexpected winding outgassing, and that's just the first handful I thought of in no time at all. The list is long. \$\endgroup\$
    – Asmyldof
    Commented Jul 21, 2017 at 0:43
  • \$\begingroup\$ @Asmyldof, I don't think the question is about life-support electronics on a mission to Mars. This is a homebrewing machine for God's sake... \$\endgroup\$
    – Ale..chenski
    Commented Jul 21, 2017 at 0:48
  • \$\begingroup\$ @AliChen And you seem to believe this adapter is made for exactly that purpose. Have you recently bought... any appliance over 15W and felt the adapter while in use at its actual limit? Not long ago I checked an HP one and it failed to operate within the stated range at 104% of rated load. "Just use whatever, what can go wrong" doesn't fit "random unknown device" at all \$\endgroup\$
    – Asmyldof
    Commented Jul 21, 2017 at 0:51

1 Answer 1

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The correct answer is, "find the appropriate sized adapter." A quick Google search found them for $6 and up.

Your underpowered fan will not operate efficiently, leading to downstream heating problems that you're not considering.

Cooling the outside of the adapter is only half the battle. You need to worry about thermal transfer from the transformer inside the adapter to the outer casing. If the adapter can't move its internal heat to the surface fast enough, it doesn't matter how cold you get it. It will eventually burn up.

If you get lucky and there are no downstream consequences and the adapter can cool itself fast enough ... then you've come up with just about the most expensive solution to the problem I can imagine. How badly do you want that brew? Remember, the correct adapter is $6+shipping.

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  • \$\begingroup\$ Interesting, ok thanks! I have ordered an adequate adapter, but just for my curiosity - what if I could cool the transformer inside. Does that make the voltage go back up? Thanks again. \$\endgroup\$
    – Stewii
    Commented Jul 21, 2017 at 0:43
  • \$\begingroup\$ Possibly, it depends on the design of the adapter. The heat isn't what's causing the voltage to drop. What's causing the voltage to drop is causing the heat. Therefore, depending on the design, you could remove every therm of heat and still not lift the voltage. \$\endgroup\$
    – JBH
    Commented Jul 21, 2017 at 0:45
  • \$\begingroup\$ Ahh, ok. I'm gonna go read about transformers. Thanks! \$\endgroup\$
    – Stewii
    Commented Jul 21, 2017 at 1:00
  • \$\begingroup\$ @Stewii, why only transformers? You didn't reveal the electrical architecture of your AC-DC adapter. Is it a mundane iron-clad AC transformer with a primitive rectifier bridge and a cap, or is this a quite sophisticated AC-DC converter based on high-frequency switcher topology? \$\endgroup\$
    – Ale..chenski
    Commented Jul 21, 2017 at 1:06
  • \$\begingroup\$ While I generally agree with the spirit of this answer, the supporting details are largely incorrect. Brushless DC fans are fairly stable (even linear) with regard to voltage deviation, see some data maximintegrated.com/en/app-notes/index.mvp/id/1784 . Regarding the internal heat transfer, the path is already there to external casing, so any extra cooling from outside will definitely have a PROPORTIONAL effect on internal temperature. \$\endgroup\$
    – Ale..chenski
    Commented Jul 21, 2017 at 1:31

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