What is the best bin for direct drive 3 or 4 cell

For all you who have some experience with direct drive.

Specific Question: What is the best Vf for direct driving a Lux III at 1000ma for a 3 cell and 4 cell NiHM cells?

Now 1000ma I mean after the battery has settled under the load for a while after charging... so initially it may be over driven at say 1300ma. Basically semi plateuing at 1000ma.

I know the variable are the total resistance of the circuit - the internal resistance of the NiMH, the wiring, the luxeons, and battery
holders (if they are used)

I've only had one experience - that is with 3 AAA rayovac 15 minute charge batteries rated at 800mah direct connected to a Lux III TWOL.
Initial current is 750ma for the first 5-10 minutes and then stays around 650-550 for the next hour.

side note - I'm really like the direct drive methods - as long as they
pull enough current - because you don't lose 10-20% of the energy which ultimately translates into runtime. Also, you're not turning that energy into heat that needs to be dissipated.

Anybody?
David

Re: What is the best bin for direct drive 3 or 4 c

Specific Answer: The higher the better.... L (4 cells) better than K (3 cells)

Re: What is the best bin for direct drive 3 or 4 c

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hotbeam said:

Specific Answer: The higher the better.... L (4 cells) better than K (3 cells)

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IMO this is the next best advice after 'don't mess with DD'. FWIW the only advantage I can see to DD is it's simple. Like most things simple, it has simple drawbacks to go with it. While those who defend it quickly point to 'no power wasted', I'd suggest that in fact it's almost always a waster of power.

By definition it's overdriven (from what the user wants in terms of output) at first, 'perfect' only briefly, then underdriven until the battery get's changed. Once you decide how much light you want, why settle for more or less unless it's a matter of not being able to have what you want because you don't know how to get it or it costs too much to do it right?

For sure those really interested in efficiency (light out for power in) aren't working the high power (very inefficient) end of things any way.

DD is marginally abusive in most lights guys design, IME. Some clearly the other side of marginal with hot of the charger cells. Reduced light output and short LED life are sure to follow. IMO a far better idea is to decide what *current* you want to drive your LED at and make that happen no matter what the battery condition. Anything else is either a waste of energy or abusive of the parts.....or both.

Doug Owen

Re: What is the best bin for direct drive 3 or 4 c

It looks like dd is best for a steady discharge power source like nimh, nicad, li-on, lithium, or sealed lead acid gelcell.
Once a steady discharge battery and lightsource are matched up without underdrive or overdrive, then a lossless dd setup can be enjoyed for most of the battery's discharge.
Good luck.
Otherwise for most average Joes, I agree with Doug Owen.