Method and apparatus for controlling battery charging current

Abstract

An automatic photovoltaic controller provides a fixed frequency, pulse width modulated charging current to charge and regulate a battery, the duty cycle of the charging current being controlled by the difference between the sensed battery voltage and a desired regulated voltage. Modulation is achieved by controlling the on and off states of plural parallel-connected FET switches placed in series between the photovoltaic array and the battery. The duty cycle is adjustable in discrete steps over the entire range of 0% to 100% and is updated numerous times per second with new battery voltage measurements to provide highly accurate regulation. The charge current pulse rise time is selected to match the response time of the photovoltaic array. The fixed frequency of the charge current is within the preferred range of 100 Hz to 600 Hz to provide sufficient time for the chemical reaction within the battery cells to be substantially completed between charge pulses during the regulation mode. Automatic protection of the controller and the load is achieved by rapidly disconnecting the battery and/or load in response to specified conditions. The photovoltaic array is disconnected from the battery at night to prevent battery discharge into the array. Equalization of the battery is performed automatically, at a voltage level slightly higher than the regulated voltage, after a predetermined number of days or if the battery voltage falls below a predetermined level.

Dependencies are inferred from the claim text.