Na(+)/H(+) antiporter that extrudes sodium in exchange for external protons. Can also transport lithium. Has a low antiport activity that functions over a large range of sodium concentrations. Optimum pH is at least 9.5, the highest pH value tested. No activity is observed below pH 8.5. Belongs to the NhaD Na(+)/H(+) (TC 2.A.62) antiporter family.