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domdymond posted on r/batteries1w
Just get a simple sla battery or a small lifepo4 battery with a built in bms for low voltage cutoff. Either one at about 20ah will run A <60w light for around 6 hours+ https://www.walmart.com/ip/15439605136?sid=5f3d8f7f-248b-48f4-9870-b48551a0e8eb