This picture shows a depleted AA battery driving a white LED, with nothing between the battery and the LED except for the wires, which should not be possible since the forward voltage of a white LED, that has to be exceeded to the device to light up, is at least 3 volts!
There is no circuit hidden in or behind the battery and holder. It’s just a plain old battery holder with a spent AA battery in it.
The component that looks like a resistor is actually a small inductor, and it was blocking the view of the smd integrated circuit chip that is soldered directly to the wires of the white LED.
The mini SOT23 chip is step-up converter that has an internal mosfet driver transistor, so the only external part that is needed is an inductor.
The ZXSC380 IC (from Diodes Inc.) is very tiny and incredibly hard to solder to the LED. The surface tension of the liquid solder will pull it out of position and I ended up having to use small copper alligator clips to hold it down while I soldered.
I should have cleaned up the excess solder but I wanted to get some pictures before I took the chance of de-soldering it by accident while reheating.
The chip is soldered onto the legs of the LED and then the wire between pins 1 and 2 is cut out so there is no connection. The inductor is then soldered so as to bridge pins 1 and 2. I soldered the inductor on before cutting out the wire but it might be easier to try some other method.
As I said previously, this is a tedious solder job, and the SOT23 IC is easily damaged (ask me how I know!) It takes patience and a steady hand to assemble these few parts.
This circuit would work for the LED indicator in the 1.5v boosters and would most likely be a better choice than the Joule Thief that I posted previously.