Here is a runtime chart for all three light modes for the HS21. Since it is clearly not recommended to submerge the light, I tested the runtime without cooling.
The modes are regulated fairly well. After roughly calculating the capacity taken from the battery (including losses due to the optics for the LED current), I arrive at around 2920 mAh for the Throw LED, which indicates an efficient buck driver.
The longest runtime after step-down is achieved with the flood LEDs.
Other measurements:
Turbo:
Throw: 1632 lm @ 15100 lx 1m
Flood: 1282 lm @ 1240 lx
Combined: 2007 lm @ 10700 lx
Moonlight:
Throw: 2 lm @ 19 lx (calculated, 1 m)
Flood: 2.6 lm @ 2.5 lx
Combined: 2.8 lm @ 14.9 lx
The values stated by the manufacturer are unfortunately not met. Even if I consider measurement errors in my setup, there is a really huge deviation in result for the spotlight LED. Also the step-down to 1000 lm stated in the manual is not met, since it stepped down to around 700 lm. But to be fair, there are no testing conditions stated in the manual, so maybe these are the reason for these values. On the other hand, the runtimes given in the manual are also veeeeery optimistic:
