Most Android phones would at least need a top-off from a charger to get through a day like that. When I toned down my usage, I found the OnePlus 15 could actually last three full days without charging. The secret, it seems, is that the OnePlus battery uses advanced silicon nanostack technology, which boosts its capacity while taking up less space than a standard battery. Wrap-UpThe OnePlus 15 rewrites the rules of smartphone battery performance and charging. The OnePlus 15 is a bit more modest in its aspirations, but also more practical.