Driver Choice for Single Li-ion red XP-E2 light?

I have a red XP-E2 for a stargazing/ night-use light with 1x Li-ion battery, I tried a MOSFET style driver but it’s “uncontrollable” and the modes doesn’t work. It seems that the light is always on max. I have considered using a 7135-based driver but I heard that they burn off excess voltage, where the lower voltage of the red XP-E2 might be a problem? Or I have to resort to buck driver?

I think that once a year this question comes up on BLF, and the answer is always that there is no really suitable driver to run a red XP-E2 properly.

What I have done is using a 5x7135 driver anyway while using a host that has the driver clamped in well from two sides (with a retaining ring), so that the ground pads of all the 7135 chips are close to the flashlight shell for easy shedding of the heat. The driver gets away with that, the red XP-E2 is well driven close to its max, but the flashlight will be far from efficient.

What size is the driver? How much current do you intend to use? Does it need modes ( I assume it does^).
XP-E2 red 1000ma max. Djozz ran a XP-E2 death test on a copper mcpcb here. blue and green XP-E2, output tests
Im thinking a AX2002 driver board might work good here such as this but no modes.

Are there no buck drivers that can buck as low as 2 Volts?
Maybe try some cheap single mode buck driver.

Otherwise use a 2x AA host with 3x 7135. Only 0.4 Volts to lose when you use NiMH batts.

AX2002 datasheet.

Convoy sells an AX2002 driver, the current is 1A, so it’s a single mode driver with wide input voltage range?

A LD-29 with a modified sense resistor might work.

PAM2804 looks like a better choice than the AX2002 IMHO, it has Vin >2.5V (and a smaller footprint and uses a smaller inductor). Don’t know if there are drivers that use it though.

I found this driver in my parts pile…

I bought it somewhere in TaoBao, and it was sold as a IR/ colored LED driver. The stated output current is 1.4A, with input voltage being 2.7-6v and output voltage being 1.4-3.6v. The modes of 100% - 50% - 5% is not my favorite, but it works.
Here are more pics…

Is this a buck driver? I had a 17mm version of this and it seems that it uses PWM to achieve the lower modes. This might be a candidate for a a red XP-E2 light? :nerd_face:

Would an AA/ 1.5V battery boost driver be more feasible for this job, since it only needs to boost to ~2.0v? Or it doesn’t work like that?

I’ve been using 6*7135 drivers for my XP-E2 hunting flashlights (Convoy C8’s) for quite some time with success. Haven’t burned one out yet.