Can I drive 3 x XR-E with 11.v pack ?

I have a Li-ion 11.1v 6600mah pack that I'd like to use to drive a new bike light. I'm thinking of using some Q5's or R2's that I already have in the box, and would like to use a buckpuck since I've used them and like the solid potting form.

But I'm thinking the math puts me on borderline of needing a buck/boost driver considering 3 XR-E's and the voltage for the driver should be right around the max voltage of my pack.

Am I on the right thought track ? Any suggestions ?

yes your on the right track, 3x running 3x is sorta just like running 1x with 1x , just 3times as many
so when battery is to high for led Vf you need buck, and long before battery is discharged fully you need boost.
so you could direct drive (with resistance) or Buck with a buck that did not drop voltage to much, either of those , you will get long running severly dwindling output.
you could boost , and you will be in overdrive, depending on other resistances in the whole package, until the voltage drops far enough.

you could boost and just toss in a bit of protective resistance, or a fat voltage dropping diode?? but then you lose about .7v the whole time about 6-8% loss of efficency, then add that inefficency to the boosts inefficency, might not be to bad. some ideas anyway.

Thanks Vidpro

For efficiency, it sounds like I should either go direct drive, or even consider going with 2 P7's or MCE's instead. I'm really looking for something floody anyway since I already have a nice triple R2 that throws good and works well on the helmet.

I assume the 11.1v battery would work ok for two P7's in serial ? Or maybe I'd need to feed them with two separate drivers to push enough amperage ?

I appreciate the feedback.

or 4 2 serial two parellel. (with appropriate drive of course)

Four XR-E's wired in series and a boost driver (like Fatman of MaxFlex) and you're good to go.

direct drive is easy _______ R1
+----|>|----|>|----|>|---/\/\/----+

At 350ma R1 = 3.9 ohms, 1/2-1W
At 700ma R1 = 1 ohm, 1W

If I was doing this, I'd use this circuit. The circuit can use any AMC7135 board of any output, single or multiple modes.

LukeA said:

If I was doing this, I'd use this circuit. The circuit can use any AMC7135 board of any output, single or multiple modes.

Click to expand...

X2

LukeA said:

If I was doing this, I'd use this circuit. The circuit can use any AMC7135 board of any output, single or multiple modes.

Click to expand...

I love this particular circuit. It allows you to do arbitrary numbers of LEDs using a single driver as long as you balance your batteries.