Let’s do some math… 15,000 lumens would require more than 150 watts. Divided by 4 batteries gives over 40 watts per battery (with driver losses). Batteries at 4V would be over 10 amps per battery. Yeah, like that’s gonna happen.
And I know how much passive heatsinking it takes to handle 150 watts (15,000 Lumen Bridgelux C9000 Light Engine) That thing would be molten slag in moments…