Abstract: A battery charger contains a transformer designed to automatically provide the finish charging current to the battery being charged at the desired levels. Control circuitry can be included in combination with the charging circuit to maintain the desired finish charging current for a predetermined period of time to bring the battery up to full charge.

Abstract: A propulsion system for an electrical vehicle including a linear proportional controller operable in a plurality of modes for operating a d.c. drive motor via power derived from a propulsion battery. Low speed operation is achieved in an armature control mode wherein the controller is interposed between the propulsion battery and the motor armature while the motor field is coupled directly across the battery. High speeds are attained in a field control mode wherein the controller is interposed between the battery and motor field while the armature is coupled directly across the propulsion battery, thereby eliminating controller losses from the high current armature circuit. Switching between modes is achieved in a manner which minimizes stress on the switching elements. The controller is also adapted to operate in a charger mode wherein unregulated d.c. power is fed to the controller which functions to regulate the charge provided to the battery.

Abstract: A power converter for operation with a d.c. power supply to provide an output voltage having a level controlled in response to an external control signal. The converter uses a dual chopper configuraton with the out of phase outputs from the respective chopper halves being combined in an interphase transformer. To prevent the interphase transformer from saturating, the chopper control includes an oscillator, counter, D/A converter and phase delay comparator arrangement for maintaining substantially identical duty cycles in the respective legs while, of course, allowing the duty cycles to be varied in unison. The interphase transformer is wound in a configuration which presents a magnetic shunt between the halves of the transformer, said shunt serving to limit transients which might be coupled to the chopper load.

Abstract: A circuit for detecting and indicating the actual state of charge of a storage battery in response to signals sampled from various points in the circuit powered by the battery. Such circuit is adapted to calculate the open circuit voltage of the battery, it being realized that the open circuit voltage is directly proportional to the battery state of charge. A function generator is constructed to simulate the characteristic curve of the battery relating the internal resistance to the percent charge. Feedback is provided from the output of the indicating circuitry to the bias point of the function generator for causing the generator to produce a signal related to the actual internal resistance of the battery. The circuit is adapted to provide a reliable indication of the amount of usable energy remaining in the battery, irrespective of the conditions under which the battery was discharged.