A charging circuit for a random access memory (RAM) backup battery for supplying a first charge current from a voltage supply to the battery for as long as the voltage supply is present, comprised of a first resistance apparatus for limiting the first charge current to a low predetermined value, a bypass conducting switch connected in parallel with the first resistance apparatus, and apparatus for detecting a low voltage condition of the voltage supply and for enabling operation of the bypass conducting switch thereby bypassing the first resistance apparatus and allowing discharge current to flow from the battery to the RAM.