On Sat, 07 May 2016 19:46:35 +0100, Winston_Smith wrote:

On Sat, 07 May 2016 18:20:44 +0100, "Mr Macaw" wrote:

There isn't much left in a battery when the light is too dim to use anyway, so thieving and extra 1% is pointless. Look at the discharge graphs, the voltage plummets suddenly at the end.

But at the same time, look at the light output vs voltage for the LED.
It plummets too. A very small boost in voltage gives a remarkable
increase in light. (It's logarithmic) The thing a joule thief really
does is control the LED current to keep light consistent. It boosts
the voltage as required to do that.

In fact, a white LED requires a lot more than 1.5 volts to even come
on dimly. If you want a single cell flashlight you have to supply a
voltage booster. It's almost free to let it jack up by another 0.1
volt to get a significant return at the end of battery life.

But you hardly notice some dimming. In fact by keeping it at full power, the battery will run out quicker.

--
The only time you have too much fuel is when you're on fire. -- US Air Force training manual.