Re: is it me or do infinity ultra\'s go forever?
They do seem to last a very long time on one battery.
However, seems to me I remember milkyspit telling how using lithiums in the Ultra Infinity would not get as long a run time as opposed to using plain old alkalines.
Ahhh, here it is.....
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milkyspit said:
Guys, here's what's happening with the Ultra. It's not regulated, but uses only a voltage boost circuit. Doug Owen and others have studied the circuit's characteristics fairly extensively, and it's clear that there's no regulation going on in there, even though the marketers call this a "regulated" light.
Now don't flame me, please, because I love the Ultra! It's my favorite of the single cell Nichia lights, and a great value IMHO. But I also believe in calling a spade a spade, and in this case, the Ultra is simply not regulated.
With that in mind, it's easier to understand the "strange" behavior using a lithium AA cell. The way the circuit works, the higher the input voltage, the higher the output current flow to the LED. A lithium AA cell has a higher voltage than an alkaline cell, plus doesn't experience as much voltage sag under load. The bottom line is that it delivers more voltage to the circuit, and hence more current flow. So far so good. But two things happen...
1. Even with an alkaline, the LED is driven beyond spec. The additional current flow from the lithium doesn't result in all that much more light, mostly just increased heat. To be sure, you can see the brighter lighting on a lithium AA cell in a side-by-side test of two Ultras, but just eyeballing a single light first with an alkaline, then with a lithium, you would have a hard time seeing it. And the heat wouldn't be that noticeable because it's not all that much heat to begin with. Certainly nowhere near the heat generation of a typical Luxeon. So to sum up this point, there
is more light, but you probably wouldn't notice.
2. The increased current flow will cause the lithium cell to deplete itself more quickly than the alkaline. A fresh lithium AA cell has 3000mAh stored energy, while a fresh alkaline has 2850mAh. Pretty close. The small advantage with the lithium will be more than negated by the light's faster consumption of that energy due to the higher current flow. That's why the lithium cell is measured as having a marginally shorter lifespan in this light than does the alkaline.
Incidentally, the reason a lithium does so well in those other lights has more to do with the alkaline being "miscast" in those lights (to use theater terminology) in the first place. Alkalines excel at delivering small amounts of current flow. They're rated for current flow of 25mA. A typical incandescent light and even a Luxeon light, though, will demand
500mA or more. At that level of discharge the alkaline will no longer exhibit its rated capacity of 2850mAh, but instead will behave as if it has
far less capacity. Meanwhile, the lithium cell will crank out these higher currents with
much less degradation of its capacity rating. So the higher the current draw, the greater the benefit to using lithium cells.
Hope this helps. /ubbthreads/images/graemlins/smile.gif
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Read the entire thread ....
here.
