So, I have these garden lights powered by solar cells. I also happen to have a power-LED over from a broken flashlight, I think its a Cree R2 or Q5 or similar. These lights charge a 1.5V 600mah Nimh battery during the day, and then light up these rectangular low-power leds.
Now I would want to experiment with simply driving a high-power LED at similar, or slightly lower power levels, meaning a very very low current. I have not measured the drive current for these, but I imagine its well below 50ma. The theory being that it will be brighter still because of the excellent efficiency of power LEDs in this power band.
I know power leds generally require current limiting or control, and that the battery voltage is not enough so I will need some sort of boost circuit if not already present.
What I am wondering is what is the most efficient way of doing this, without being overly complicated? Is it possible to do this with just a resistor, or am I still prone to current run-away at these low levels?