3c LuxIII Mag vs. 1D LuxIII Mag?

Had a few questions about a build dilemma.

I know the runtime on a DD UxxK binned LuxIII 3c Mag will have a ~5 hour runtime, using 5000mAh NiMH C cells.

But, how would a 1D UxxL binned LuxIII, direct driven by 4x 2500mAh NiMH AA to 1D adapter fare up?

In terms of peak brightness length and total runtimes?

Size isn't my main concern, but if I can get the nearly the same performance from a smaller package for a little more money, i'm gonna go with the latter of the two.

In terms of cell capacity:
3x C cells = 1.2 volts x 3 cells x 5Ah per cell = 18 watt hours
3x AA cells = 1.2 volts x 4 cells x 2.5Ah per cell = 12 watt hours

If your lights were regulated and had the same voltage bin and were run at the same drive current, then the C cell light should run for 50% longer.

But, that's not the case here. You say these lights are direct drive. The K bin is 3.5~3.75 volts, and the L bin is 3.75~4.0 volts. I'm guessing the L bin in the 4xAA is going to be driven pretty hard, and will be brighter than the 3xC. I'm also guessing the 4xAA will last for quite a bit less time than the 3xC because the AA cells hold less juice, and the higher voltage is going to result in a higher drive current.

If you throw in a driver with the 4 AA,s to regulate current to the led, then that would be better but cost more. Pretty sure the C's will still win in runtime even vs 4AA with a buck converter.

Excellent answers Ty. You're exactly right. I have both of these setups and the 1D with 4AAs DD a UX1L does, in fact, outshine the 3C DD UWOK for a short time. The 1D, however, dies out quickly when drawing about 1.4 amps on fresh cells.

The 3C last much longer than 5 hours. As the voltage drops, the current drops. Now you're drawing less current and the LED runs more efficiently. I'd expect about 8 hours of usable light from three fully charged Cs in this setup.

The 1D is an excellent size and i prefer it to the 3C. I'd recommend installing a regulator in that 1D to improve your runtime. You really get diminishing returns on brightness after about 1amp so you should limit you current through the LED to 800-1000ma. This will give you 3-4 hours of bright light from your 1D.

Also consider the charging systems involved. Do you have a charger for 3-4 'C' batteries? Finding a charger for 4 AAs is easy. You can substitute alkaline and lithium primary AAs in a pinch.

If you settle for a 'T' bin emitter you can improve your runtimes even more. TxxH Lux III emitters are readily available and much less expensive than 'U' bins. You will definitely need a regulator, but the much lower Vf will save you 1watt every hour and increase your runtime by 25% over a UxxL.

I'm fairly new to the convertor (regulation) board territory, so correct me if i'm wrong -
(I'm using Mr.Bulk's guide to building a space needle as Mag building reference.)


Installation of the board would be inside the back of the Hotlips, with thermally conductive epoxy filler.
The wires from the top of the board get soldered to the Luxeon + and - leads.
The wires from the bottom of the board get soldered to what? (I plan on using a Tailcap Switch).
Also, what convertor board do you guys recommend? The resistor values have me confused.