Method and apparatus for controlling battery charging current
First Claim
1. A photovoltaic controller for controlling delivery of charging current from a photovoltaic array to charge and regulate a battery to a voltage Vr while the battery is driving a load, said controller comprising:
- switching means connected in series in a charging current path between said array and said battery for alternatively passing and interrupting charging current through said path;
battery voltage sensing means for sensing the voltage across said battery;
means for comparing the sensed battery voltage to Vr ; and
control means for cyclically actuating and deactuating said switching means in a fixed frequency, pulse width modulated mode, said control means comprising pulse width adjustment means responsive to said means for comparing for varying the duty cycle of said pulse width modulation such that the time for passing a charging current pulse during each cycle increases in response to a battery voltage less than Vr, and decreases in response to a battery voltage greater than Vr.
1 Assignment
0 Petitions
Accused Products
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.
61 Citations
33 Claims
-
1. A photovoltaic controller for controlling delivery of charging current from a photovoltaic array to charge and regulate a battery to a voltage Vr while the battery is driving a load, said controller comprising:
-
switching means connected in series in a charging current path between said array and said battery for alternatively passing and interrupting charging current through said path; battery voltage sensing means for sensing the voltage across said battery; means for comparing the sensed battery voltage to Vr ; and control means for cyclically actuating and deactuating said switching means in a fixed frequency, pulse width modulated mode, said control means comprising pulse width adjustment means responsive to said means for comparing for varying the duty cycle of said pulse width modulation such that the time for passing a charging current pulse during each cycle increases in response to a battery voltage less than Vr, and decreases in response to a battery voltage greater than Vr. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 21, 22, 23, 24, 25, 26, 27, 28, 29)
-
-
15. A method of controlling the charging current applied to a battery from a photovoltaic array while said battery is driving a load, said method comprising the steps of:
-
(a) applying said charging current to said battery continuously when the battery voltage is below a first predetermined voltage; (b) applying said charging current to said battery in pulses of a fixed frequency pulse train when the battery voltage is in a narrow range surrounding a desired regulation voltage; and (c) controlling the duration of said charging current pulses as a function of said battery voltage over a duty cycle range extending from 0% to 100%. - View Dependent Claims (16, 17, 18, 19, 20, 30, 31, 32, 33)
-
Specification