Driver Suggestions

I have been searching for a week or so for the ideal driver for a particular mod. I'm just not finding any combination I really like. Being somewhat less-experienced, I'm guessing I'm overlooking an option or two.

The light is a triple Nichia nvsl219at-h1 b10 bin (3vf) driven by two 18650 LiIon batteries. I have read repeatedly that series connection of the diodes is greatly preferred over parallel, so my driver search has been directed that way. It seems that the vast majority of drivers won't handle the voltage of the batteries in series. I'd really prefer not to have to build an in-line/parallel battery pack.

Atr this point I've narrowed it down to the Blue Shark and MaxFlex, but using the MaxFlex further complicates the build as it needs a momentary-contact switch and there's really no simple way to execute this cleanly. Plus, neither driver will do much over 1A and the Nichia output chart shows 1500mA as a very nice point to drive the diode. I also looked at the LED Senser driver from PCB Components in Germany that seems to match the application well, but as a noob, I'd really like to have some support available and that driver isn't really mentioned much around here.

I've looked at some of the pre-built approaches, such as the Oveready/Torchlab dropin which will accommodate 8.4v, so I feel fairly confident what I'm trying to do is doable (although I'm baffled at how they achieve 1600lm).

Any and all suggestions are greatly appreciated.

Maybe something like this http://www.kaidomain.com/product/details.S020909

The key is the switch current limit for the boost IC on the Blue Shark. It is rated at a minimum of 3A, although if you search CPF Wayne may have derated it down to 2.5A (don't know if the dual diode fix brought it back up to 3A).

So what you want to do is look at the worst case input current, which occurs at the lowest operating battery voltage (i.e., when your cells are heavily drained). With a 2x18650 battery source, presumably in series, your best case is at the start with Vbatt = 8.4V. Worst case is probably when the cells under load are around 3V each (6V total), when they are just about depleted. I don't know anything about the Nichia LEDs, but if their Vf is 3V at 1.2A drive, then your total Vf is going to be 9V.

If we assume 80% driver efficiency, we can estimate the input current:

driver efficiency * Vbatt * Ibatt = Vf * If
0.8 * 6V * Ibatt = 9V * 1.2A = 10.8W
Thus, Ibatt ~2.25A. So it looks like you will be ok at least in terms of the electrical limits of the driver. We can do a sensitivity analysis and assume that the driver efficiency is say 75% instead of 80%. In that case, we get Ibatt ~2.4A. Still looks ok.

What if the LED Vf is more like 3.1V? Then total Vf is 9.3V and Ibatt could be (9.3*1.2)/(0.75*6) = 2.48A. Still ok, even wrt a derated switch current spec. However, if Vf is more like 3.5V at 1.2A drive, then Ibatt ~2.8A and you may be in trouble if the Blue Shark is still derated.

Assuming that you are ok, the key will be to make sure that your thermal management is up to par to keep the driver cool and to remove the waste heat from the LEDs. The driver is going to generate close to 3W of waste heat and the LEDs will probably throw off an additional 7W-8W.

To get 1.2A drive from the Blue Shark, you need to change out the sense resistor from 0.10 ohms to 0.083 ohms.