Dale go ahead and try it with a jumper instead of the diode. As Crux points out it could very well change the resistance of the FET enough to result in higher amps.
Can’t get any higher than a direct connection to a cell, and that nets 3.16A, which is about where I’m at in the light. So the little Efest IMR10440 has hit the ceiling. Is there a fet out there that’s gonna boost the cell?
I’m going to mention this now so you have someone to blame if it ever comes into existence: XPH70 penlight. 2xIMR10400 and a reflector slightly taller than the LED.
I don’t think ICR can cope with the heavy drain (that the XHP50 and XHP70 would demand to justify putting it in a light instead of an XM-L2/XP-L2) that well.
If I’m putting an emitter that expensive into a light, I’m going to drive it hard enough to justify the cost.
Due to the small size of this driver, an SOD-323 Zener diode is best.
Simply install the load resistor in place of D1, then place the Zener diode horizontally between the bottom of that and the bottom of C1.
Due to the small size of the Zener diode it can also be installed entirely below the D1 position (eg next to the FET).
In either case the cathode of the Zener diode will face the ‘D1’ identifier (PCB marking) and the anode of the Zener diode will face the outside of the PCB.
The grammar makes the statement hard to decode. It almost sounds like he is saying that an XHP70 being ran off of 2S IMR10400 is too much or that he won’t even consider the 2xAAA formfactor, the first is absurd the second is personal preference.
I consider risk of running unprotected cells down an acceptable risk if it means I’m able to build a flashlight that is a satire of the FL1 standard (by having the light start out at around 3A and then after the initial measurement, it takes it down to 11% output so that it can run for almost an hour at ‘2000’ lumens).
Cell reversal is unlikely IMO. What is the minimum Vf of the XPH70? I know an XML has a minimum Vf of around 2.2v and at that voltage, current draw is pretty much nonexistant. Min vf for any significant current flow was 2.3v so a 2S2S die config for the XHP70 shouldn’t be able to reverse cells. It may kill the cells if you leave it on for hours though. Does this driver have voltage monitoring?
I think it’s doable to run a 6V led from 2 x 10440 but even though the voltage works the current supplied by a 10180 cell even if an IMR were available is just too small. It might work but only as a novelty. Quite often what seems like a cool idea won’t work too well and 2 x 10180 to an XHP50 on a 10 mm SinkPad in a solitaire sounds to me like a good way to waste some nice parts. Bummer. 2 x 10440 in a AAA Minimag makes a bit more sense( well, relatively speaking a bit more).
It does? Good. It won’t absolutely need protection PCBs to prevent overdischarge if the voltage monitor can be set for a reasonable voltage.
I never really expected 2xIMR10180 to give satisfactory results, I was trying to figure out what you would bring up the 2x10180 config for since the smallest cell I regard as useful is the 10280 and only in something with a decent output selection. What is the point of using the XHP LEDs if you aren’t taking advantage of the extra output?
For 2xIMR10400 I was thinking penlights. That would be a “That’s not a light, whips out penlight Now this is a light!” kind of light.
Just me being silly since I have some 10180’s. I looked for the 10280’s but they were out of stock at the time. I agree with your second point which is why I recanted. I think the XHP LEDs would be outstanding in applications where a tight beam isn’t required and the high voltage allows for lower current power transmission such as canister dive lights or bike lights with remote power packs.