What driver to use for 4xP7 running off 2S3P 18650?

[jchoo]

I'm trying to work out a design that implements 4x SSC P7s and a 2s3p configuration of 18650 cells. In my head I'm thinking that running the LEDs in 2s2p and direct driving them would be fine, but I'd really prefer to have a driver (or drivers) so I can step this thing down if I want to. Does anyone have any suggestions, or should I just build the beast and make it DD?

 

[LED Zeppelin]

I built a similar quad-P7 running 2p3s 17670s.

I used triple Sharks sharing one pot. Not an easy mod, but it works well and is seamlessly dimmable from 2.7A to zero. The Sharks need to be well sinked. They get hot at that level of boost, nearly 100% (Vin/Vf), and are not particularly efficient in that range, but it's certainly not a light I built with efficiency in mind.

Be prepared for some serious heat generated by four P7s running at spec. It's the second hottest light I've built, the first being the Moby **** Trinity (tri-Ostar + tri-Cree) driven by the same Shark setup.

You will probably need more than one driver unless you have unlimited space and can fit something huge. And if you want dimming, they need to be capable of sharing one control. That limits your choices of off-the-shelf drivers.

The Sharks are compact and I could fit up to 4 in front of a Mag D switch with heatsinks if needed. Usually I use 3 and a pot and though tight, it all fits comfortably. For high power lights, I add heatsinks cut from brass shapes to the top of the IC and a dog leg on the diode. Here is a pic of the running gear for a Trinity.

 

[mitch79]

I'd use one of the drivers & PWM dimmers made by Der Wichtel.
Shouldn't have a problem driving 4 P7's in series.

http://www.candlepowerforums.com/vb/showthread.php?t=201981
http://www.candlepowerforums.com/vb/showthread.php?t=199533

 

[DaFABRICATA]

My God LED Zeppelin!!! Thats just amazing that you can fit all that in there!

PM incoming...

 

[jchoo]

Thanks for the replies. I'm still conceptualizing the light right now, but I think I've decided how I'm going to have it all laid out. No off the shelf body or head, but I would like to use readily available optics and drivers. I like the beam profile of Britelumens' 3xP7 M6, but I want a beam with a narrower hotspot and more throw. Are there any optics available that can give a similar beam profile to a Surefire E2DL? Heat isn't really going to be a factor in this. Because I'm going to be building the head and body, I'll ensure that there will be sufficient heat sinking for all drivers and emitters. I'd also like to build a charger based on this schematic - I've used it in the past to charge 2x 14500 cells in series for R/C cars, and I'm pretty sure it will work fine for a 2s3p configuration (provided all cells are balanced) - and have an integrated charging jack.

I guess that brings us to the use for this light. Well, it's a few things. First off, it's an exercise. Second, I will use it for SAR and on scene at nighttime motor vehicle accidents. Third, it's a toy... something I can pull out of my bag and place on the table and people won't be able to resist turning on something smaller than a 3D mag and being hit with 3k lumens. I'm hoping that with this battery configuration and driving the emitters at 2.8a I can get at least 70-90 minutes of runtime... I think that's pretty reasonable.

:devil: