It has been more or less established that HD12 with LiIon batteries uses PWM controlled by FET. I swapped white LEDs to 519a 5000 K. I also use F15 battery with it, which works great.
Thanks to Simon’s generosity with another light, I have a surplus of H10, which should have lower sag on Turbo. HD12 may be using a timed step-down (though I not that sure as it seems to step down quickly whan hot in certain scenarios). I noticed that the light gets hot quicker on H10 than on F15, though it may well be placebo effect.
What are the chances of burning the LEDs if the batteries are ‘too good’, having low internal resistance like H10?