Driver for MC-E?

[foxtrot824]

I'm trying to find a driver for an MC-E I am running in a surefire KX2 head. I would like to run each die from 350-500ma. I would like to keep it a single cell setup running RCR123s. I'm not sure of several things. 1 should I look for a 1400ma-2000ma driver and wire it in parallel or 2p2s run at half the amperage? 2 can I run this setup on 3.6v or am I being unreasonable? I think I would just like one mode, off and really bright :whistle:. Maybe a low and high that just depends on what exist. Any suggestions would be appreciated.
Thanks

 

[Justin Case]

Here is the key equation:

driver efficiency * Vbatt * I batt = Vf * If = watts fed to the LED

If you want to drive each die at 350mA, then you are looking at feeding the MC-E about 0.350A * 3.2V ~ a little over 1W per die, or probably around 4.5W total. If you want to send 500mA per die, then you are looking at sending probably about 6.6W total.

With one RCR123A cell, Vbatt will be around 3.7V. If we assume the best case of 100% driver efficiency, then

Ibatt = (4.5W or 6.6W)/3.7V ~ 1.2A or 1.6A.

Regular RCR123A Li-ions are usually around 500 mAh, so that the recommended 2C discharge rate is about 1A. Thus, you probably should use IMR16340 cells for this application.

Whatever driver you consider, it has to be able to accept 1.2A or 1.6A input minimum (in reality, probably more than that since driver efficiency is not 100%) to be able to output 4.5W or 6.6W to the LED.

For a typical efficiency of 80%, your driver needs to accept input currents of about 1.5A or 2A, for 350mA or 500mA drive current per die.

For your application, the 1400mA AMC7135 linear regulator board comes to mind (assuming it fits), running the MC-E in 4P. Efficiency is essentially Vf/Vbatt, or about 3.2V/3.7V~86%.