Abstract: A battery charging circuit includes a ferroresonant transformer having a rectified output for providing a constant output voltage to be supplied to a battery to be charged. Battery temperature is sensed providing an input to a control circuit which operates a shunt regulator associated with the ferroresonant transformer to provide battery charge voltage as a function of battery temperature. In response to a high battery temperature the controller functions to lower the output voltage to the battery, and in response to a low battery temperature, operates to provide a higher output voltage, with suitable control for any battery temperature between minus 10.degree. and plus 150.degree. Fahrenheit. As the battery approaches full charge and battery acceptance current falls below a predetermined level, a charge cycle termination control allows charging to continue for a period preset by the operator, at the end of which period, line voltage is removed from the charger thereby terminating the charge cycle.