In order to achieve the specified luminosity of 2900 lumens, however, requires the TK75 four 18650 lithium ion batteries and a special charger. Who wants to be sure to bring even a multimeter to the voltage of each cell before and after charging to check, because a faulty battery can lead to thermal runaway in exceptional cases, despite the many security measures in lamp and charger. Of this, however, I can find very few documented cases. This is to be careful with these batteries only as a note. I recommend buying rechargeable batteries with protection circuit, cost 15-30 per piece.
Who is not afraid of this total investment of about 300, receives a flashlight for life, because the minimum illumination time of the LEDs are specified at 50,000 hours. Consequently, one can thus 13.7 years long every night lights 10 hours straight :)
To reach: It is indicated with 690 meters. For my first test I could with slight haze in the air loosely to the other side of the Rhine are lit, the distance I have with Google Earth measured. Effectively were eventually 420 meters. The lamp in clear air to the 690 meter comes, I can imagine, but it will then be difficult to even make out an object without binoculars (:
