Abstract: A microprocessor controlled battery charger to charge a battery when the charging current is reduced to zero even though the charger is still connected to the battery. The microprocessor includes a means to read the voltage of the battery and also includes a timer. The voltage of the battery is periodically read and when it decreases below a predetermined value the microprocessor again establishes recharging of the battery first at an intermediate rate until either a maximum voltage is reached or a minimum dv/dt is reached and then the current is reduced to a lower current rate for a finishing charge of the battery for a given period of time.

Abstract: A microprocessor controlled battery charger utilizes a high frequency switching circuit and a means to read the voltage of the battery plus a timer in the circuit wherein the microprocessor is connected both to the timer and to the voltage reading means and establishes a decreasing step charging rate of the battery so as to charge the battery at a first charging rate, then at a second lower charging rate until the rate of change of voltage with time is less than a small amount of volts per hour and then the current is reduced to a third charging rate for a finishing charge of the battery. In the preferred embodiment the first charging rate is maintained until a predetermined battery voltage is achieved and the third charging rate is maintained for a given period of time.

Abstract: A spark suppression circuit for a battery charger includes a large filter capacitor connected in series with a semiconductor switch across the terminals of the battery charger. The battery charger does not have any output voltage even though the input is energized because the circuit includes a device to delay supplying of voltage until after the charger output terminals are connected to a battery to be charged. The semiconductor switch is non-conductive until the battery charger output terminals are actually connected to the battery to be charged. At this time, a bias circuit connected across the charger output terminals supplies a bias to turn on the semiconductor switch so that only at that time is the filter capacitor connected across the charger output terminals, and hence this suppresses the possibility of a spark upon connection of the charger output terminals to the battery to be charged.