Abstract: A battery charging circuit comprising means to supply a DC output from the mains supply for inter alia recharging a rechargeable battery, switch means in series with the battery across the DC output which are normally closed but which open from time to time to disconnect the battery from the DC output, battery voltage monitoring means for measuring the potential or emf of the battery at the time when the switch means are open, and means for determining a maximum potential and therefore fully charged state for the battery and decreasing the charging current from the DC output to the battery when a fully charged state is determined.