Abstract: Construction and operation of an oilfield molten salt battery. A battery includes an outer case, an elongated mandrel positioned within the outer case, and the mandrel being an electrical component of the battery. Another battery includes an electrical pickup, and a polymer insulator providing insulation between the outer case and the pickup. A method of charging a battery for use in a subterranean well includes the steps of: providing the battery including an electrolyte, and anode and cathode electrodes, the electrolyte being a molten salt comprising lithium salt, and at least one of the electrodes comprising lithium atoms; positioning the battery within a wellbore; and then charging the battery. Another method includes the steps of: heating the lithium ion molten salt battery; then charging the battery; and then positioning the battery within a wellbore.