Happy Life USB mug warmer made me very uncool

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Product: Electronic USB warmer
Manufacturer: Happy Life!
Location: somewhere in China
Price: $ 5 (including 21% vat) [!]

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THE IDEA is simple yet makes you wonder "why": draw a few milliwatts from your delicate PC mobo to warm a cup of coffee, or in my case, tea. But this warmer is definitely not "cool".

Let me start by saying that the whole idea of placing a resistor on the USB bus, with the potential of burning a trace of my desktop PC's motherboard or the notebook's made me very nervous. I plugged this contraption on the notebook and luckily for me, the system kept running. I turned on the power switch on the device, expecting a red light inside the switch but instead got nothing, no visual cue. Still, by placing the my hand over the round metal area where you are supposed to place your cup of hot beverage, I began noticing how it slowly, very slowly, began to get warm.

Top and Bottom view of the contraption

At some point, the centre of the metal surface -which actually feels like a piece of beer can- got warm, very warm, yet not hot to the point of "it'll burn my skin". Yet strangely, the outer region of the metal circle remained at room temperature. By circling my fingertips on the metal surface, I was able to find that the actual centre of the heat was less than an inch. Since the unit generates so little heat, apparently the rest of the metal surface actually acts as as heat sink. The only "heat" you can feel is right at the centre of the surface, in an area about the side of your thumb's fingertip.

So, I placed a ceramic tea mug, the kind of which we use down here at INQ GauchoLand Central. I measured the tea, and it was at room temperature. I touched the metal surface and it was "very warm" yet not "burning hot" -as explained in the previous paragraph-. I placed the cup on top of the device and left it there... for twenty minutes. At the end of the 20 minutes, I tasted the mug of tea... it was still at ambient temperature!. So I immediately touched the base of the tea mug: it wasn't even warm!. I touched the tin metal surface of the device, it was at its usual "moderately warm" temperature.

Top: barely warm outside, warm in the centre
Bottom: the empty depressing guts of the device: a resistor between two metal pieces

I don't have a digital IR thermometer so you will have to believe in my sensory information. Evidently the very low heat generated by the device, in such a small area just at the centre of the metal circle, was not even enough to heat the ceramic mug, not even to the point of getting warm to the touch. How could they expect to even get the beverage inside any hotter if it cannot even affect the mug you place on top of it?.

I opened it, and saw the guts of the contraption: just the +5 -5 volt cables connected from the USB bus, with the +5 volts one passing through the power switch, and then a round ceramic resistor in the middle of the tin surface, about half an inch wide. That's it, end of story. Remember that the USB bus only can supply a maximum of 2.5 Watt of power to be shared by the whole bus -in other words it cannot exceed 2.5W.

A mug of tea at room temperature placed on working device

I don't know if the guys at "Happy Life" mis-designed this warmer, of this is indeed the maximum amount of heat you can get off the USB power lines without damaging the system board. In any case it doesn't serve it's intended purpose. Well, let me correct myself. Maybe under laboratory conditions, with a cup of tea the size of a teaspoon, with a tea cup made of tin rather than ceramic, with the room temperature above 30 degrees celsius, and with no wind blowing, then perhaps under such kind of laboratory conditions this device can actually warm something else than your hand to the touch. Thinking that the mug was at fault, I replaced the gren mug for a flat-bottomed white one, and after 20 minutes the tea's temperature didn't change. Who knows, perhaps this device needs custom flat-bottomed thin-as-razor cups and mugs?.

The same mug, 20 minutes later, still at the same temperature

Suspecting that my Gateway 7422 notebook was at fault, I repeated the scenario with my desktop, sadly with the same results. I thereby suggest people looking for a cup warmer to please stop abusing PC design specifications and get a cup warmer of the kind that are plugged directly to the 120v or 240v -or whatever it is you have in your country where you are reading this- AC mains. You can find some here on Nextag.

The Good: you can cut the USB cable and use it for something else. Or, you can use it to warm one of your feet.

The Bad: you can only warm one foot at a time. If you plug two of these you could likely blow your motherboard.

The Ugly: it didn't warm a mug of tea for me. In fact neither the tea nor the bottom of the mug got even moderately warm, so it's not even of use for keeping hot coffee or tea at a constant temperature, if it cannot affect a the temperature of the ceramic mug's bottom

And please, our resident batch of nitpicking readers: don't bring me the "well, at least it doesn't have the same temperature loss as when the mug is placed on top of a cold surface" angle. Get a 15w cup warmer connected to the AC mains and you'll see what is a *real* mug warmer. This is a toy.

I found another use for it: stress relief

Conclusion

I have seen other "USB warmers" out there that look more elaborate, and which are made of aluminium and include a metal coffee mug, you might want to try one of those. That makes more sense and in that case there's some chance that actually that tiny amount of heat generated from the USB bus can get to the liquid and keep it warm. But you should avoid this one like the plague. The moment you read Chinglish inscriptions on the packaging like "Good Ideal!" you know it's something worth avoiding.

Bartender's report

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See also:
Chinese Power Strip so poorly made it's risible