Driver + LED Advice 2AA / ~2 Amps at the led?

Hi Guys

It's been a while since my last post, and I didn't read the forums as regular as before, but I have a project in my head, that I need a little advice for.

I want to build a helmet light for our weekly evening MTB ride, I do have a good light at the handlebar, but I want to build something for the helmet, which will only be used on the down hills, therefore weight is key, runtime doesn't matter too much. I don't want to have a cable going to my backpack. I do not want to have any Li-Battery on my helmet, that's why i want to go for 2AA NiMH.

I'm thinking maybe a XM-L2 t6 at arround 2.5A, that would mean let's say 3.2V (correct me if I'm wrong):
2AA Eneloop = 2.4V * 2Ah = 4.8Wh

4.8Wh * 0.7 (let's say 70% overall efficiency) = 3.36Wh

2.5A * 3.2V = 8W

That would give a runtime of about 25mins, which would be just enough. So maybe runnig it at 2A would be more suitable.

long story short, is my led choice any good?
Any driver recommendations 1.4v-3v input, 2Amps output? Paralleling multiple drivers could be an option I think - suggestions?

Cheers, Nico

I've NEVER been able to find a driver that can do this, which is the biggest reason I really don't care for 2xNiMH lights. Two AA batteries certainly have the power to run an XM-L at even 3A (albeit not for long before they're discharged). But when it comes to drivers, 1A is all you are going to be able to find. You COULD try using two 1A drivers in parallel. But if you are building something yourself and can go with any number of cells, a better idea would be to use 3 NiMH cells (or, depending on the driver, maybe 4). That way, any 1x18650 driver will work for you.

I know you say you want to keep the weight down. But one extra battery is a fairly negligible increase in weight, especially in comparison to the performance increase you get from 3xAA vs 2xAA. Simply put, when it comes to the performance of lights and drivers, 3xAA is like 1x18650 while 2xAA is little to no better than 1xAA.

Hi StorminMatt

I know increasing the cell number would make it easy, but I really want to build it as light as possible. So, I guess I'll go with the paralleled drivers, as I thought before, it just seems to be the only options.

Anyway, thanks for the input

Regards, Nico