'Battery', like AA or AAA?
The gold standard was the now discontinued B&M Ixon IQ, 4xAA. A few are still available here and there; get 'em before they're gone.
Still available is the less impressive but okay Cateye GVolt25C, 3xAAA.
There's the Fenix BC30 V2.0, 2x 18650 or 4x CR123A. You can practically arc weld with one of those.