I have this circuit from a flashlight that runs an LED with just 2xAA batteries. Initially I thought it used a boost converter or a joule thief but when I opened it up I found that it did not. It depended merely on the 3V those two Alkaline or Zinc Carbon cells output in series to light up the LED at it's minimum voltage at 3V. Problems arise when the voltage of these primary cells drop after a while making the light very weak.
So I decided I want to modify it and make it run on two NiMh cells at 2.4V. I have attached the circuit below. Can I add components at just these 2 green points to make the joule thief work? Also there is not much space inside the flashlight to place a toroid, just enough space to squeeze a transistor and a couple of tiny components. I hear there exists Joule thief that uses discrete axial inductors and or ceramic caps?
Here is the latest Schematic. There is an additional point where I can add a component, that is the resistor point. I can de-solder the resistor (orange point) and add a component there if needed. The green points remain unused so anything can be added there.