George DornFinally, I have sourced and soldered all of the parts for a D&D mini-painting battery-powered lamp: It's using a Dewalt 20V battery, four Bridgelux V8D LED COBs (at 3000k, the same as the light in the D&D room), a MP1584EN DC step-down (to ensure a constant 16V), and a potentiometer+resistor to limit current. I tried not using the Vreg, but the math suggested I'd melt things. Next step: Goodwill for a donor lamp, and 3d-printing a battery mount / base.
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