Batteries (50) containing oxidized, discharged metal electrodes such as an iron-air battery are charged by removing and storing electrolyte in a reservoir (98), pumping fluid reductant such as formalin (aqueous formaldehyde) from a storage tank (106) into the battery in contact with the surfaces of the...http://www.google.com/patents/US4448858?utm_source=gb-gplus-sharePatent US4448858 - Chemically rechargeable battery
