To operate the light at the full 9000 lumens, you would definitely need to have a cause for that many lumens with that much throw (938 feet). Fenix identifies the TK72R was specifically designed for search and rescue or industrial tasks, etc. Operating at a
sustained 9000 lumens for general use may not be necessary. For example, around a campsite, you may want to check your surroundings at night. Would you need to check up to 938 feet away? If so, bump up to 9000 then step down to an output appropriate for the environment. We hope this makes sense. To preserve battery charge, it is important to operate a light at the output level to match the surroundings. We know you CPF users understand this. We just have to emphasize this to general users often to help them understand it isn't necessary to use the Turbo mode of the PD35 (960 lumens with a throw of 682 feet) when they are working on the plumbing underneath the kitchen sink.
As far as recharging, it is recommended that you NEVER let the batteries drain completely. When your light arrives, it will take approximately 6 hours to get a full charge on the batteries. After that, you will have the battery level indicator on the OLED screen to let you know the levels. Of course, the more it is drained, the longer time to recharge.
Please let us know if you have any specific, technical questions for the Fenix engineers. We will be glad for forward your questions to them for answers.
So (approximating from graph)… 10 or 15 minutes at full tilt 9,000 lumens before dropping to somewhere around a quarter of that for a couple more hours? Not that 2,000 lumens is anything to complain about. Just trying to figure out what one actually gets for the money. I wonder how long it would take to recharge this thing once the battery is drained dry.