There are a number of batts that will work well for a single 18650 device like the NEBox. The most affordable suitable OEM batts are Samsung 25r's, (2500 mah). Other favored models include Sony VTC4's, (2100 mah), VTC5's, (2600 mah), Panasonic 30Q's, (3000 mah), LG HE2's, (2500 mah), and...