One 123 cell driven Luxeon III?

Hello,

Can someone tell me if a Luxeon III driven at spec 700ma, how long will one 123 cell last?

I am planning to mod a single cell Luxeon III, is there any regulation circuit avaiable best suitable for this?

Many thanks /ubbthreads/images/graemlins/thumbsup.gif

123 cells are typically 1400 mAh.

Assuming a perfect boost converter and nothing complex like voltage sag, you need ~860mA from the 123 cell @ 3V to get 700mA @ 3.7V at the load. Add 15% converter overhead and you get ~990mA at the 123 cell, which is about 1.4 hours or 84 minutes.

You could use a pair of LEDDynamics' 2009 MicroPucks to get 700mA @ 3.7V, but 2 of those will cost more than the average LuxIII...

[ QUOTE ]
idleprocess said:
123 cells are typically 1400 mAh.

Assuming a perfect boost converter and nothing complex like voltage sag, you need ~860mA from the 123 cell @ 3V to get 700mA @ 3.7V at the load. Add 15% converter overhead and you get ~990mA at the 123 cell, which is about 1.4 hours or 84 minutes.

You could use a pair of LEDDynamics' 2009 MicroPucks to get 700mA @ 3.7V, but 2 of those will cost more than the average LuxIII...

[/ QUOTE ]

No chance you'll get anywhere near 84 minutes of runtime. The 123 just can't provide that level of current without large internal losses - you REALLY have to factor in the voltage sag. I would venture to say that any driver that's in the 90% efficiency range will be lucky to give you 40 minutes of 700mA runtime from a single 123.

At ~1A a 123 will sag rapidly to 2.5V, been there, done that... Then you're look at 3.7V x 700mA/90% = 2.88Watts input power. From 2.5V that's 1.15A - not 123 friendly at all. 2xAA nimhs would be a much better choice - though not as compact.

george.

...and like fluid dynamics equations that conveniently ignore things like pipe wall friction and temperature effects, "something complex" thoroughly breaks the simple linear example.

50-60 minutes, tops.

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this_is_nascar said:
50-60 minutes, tops.

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40 minutes will be it with 90% efficient current regulated drivers from a typical 123 and K binned Lux3.

george.

I have a arc ls running at 750ma with a unknown bin lux3.I get about 30/40 min. tops.

How about a pair of AAs side-by-side... it'd be thiner than a single 123? rechargeable required.. no way to get the current to drive 3W from alkies. I am planning on variations on minimighty that include 2AA, 2AAA, etc.. i think you can get an over an amp for over an hour out of a single AA NiMH.. probably closer to 2A... so it should work well. (driver is the issue, but i think fatman would do the trick)

reviewing run time charts:
tests using a BB650 on a single 123 run about an hour.
same tests using a BB750 give us 45 minutes or less.