Chloride Group Limited

George W Foster

The automatic electric battery charging apparatus includes at least one timer, a voltage comparator arranged to compare a reference voltage, referred to herein as a staircase voltage, with a control signal varying with battery voltage, jacking means rendered operative by the timer when a first predetermined time interval has elapsed and serving to repeatedly increase the staircase voltage step-by-step relatively to the control signal, by equal steps, so long as the control signal exceeds the reference voltage, and terminating means for initiating the termination if the staircase voltage exceeds the control signal before the jacking means have exceeded a predetermined number of steps from the start of their operation.

Automatic electric battery charging apparatus

A battery charger which provides a constant current charge during a first part of the charging period and a taper charge during the remainder of the charging period. The taper charge characteristic is obtained by decreasing a set value for the charging current by a step of predetermined size each time the battery voltage has risen by a step of predetermined size, provided that the battery voltage is above a certain threshold; below this threshold, the set value has its maximum value, resulting in the constant current part of the charge. The charging current is regulated to be equal to the set value, regardless of variations in mains supply voltage. The charge is terminated when the time between steps in battery voltage exceeds a predetermined value.

A controller for incorporation in a battery charger to limit the overall length of the charge, and also to provide short topping-up charges at intervals after the main charge has been completed, if the battery is left connected to the charger. The controller allows the limit on the length of the charge to be set to either 10 or 141/2 hours; the subsequent topping-up charges then start at intervals for 10 or 141/2 hours, and last for about 40 or about 55 minutes, depending on the setting of the main charge time limit. The controller is illustrated in conjunction with a charger control circuit which terminates the main charge when the rate of rise of battery voltage falls below a predetermined value, and this is normally expected to occur before 10 (or 141/2) hours have elapsed, leaving the time limit set by the controller as a safeguard.

Automatic battery charging apparatus in which a control signal is generated by subtracting a signal representing a fraction of the mains supply voltage from the battery voltage so that the control signal represents the state of charge of the battery irrespective of variations in the mains voltage. The charge is terminated when the rate of rise of the control signal falls below a predetermined value; this condition is sensed by sampling the output frequency of a voltage controlled oscillator whose frequency is directly proportional to the control signal. In one arrangement the output frequency is fed to an up-down counter for a sampling period (2 minutes) with the counter counting up and then, after an interval of 30 minutes, the output frequency is fed to the counter for a further sampling period (1 minute 55 seconds) with the counter counting down. If the counter fails to return to zero at the end of a down count the charge is terminated.

An automatic battery charger of taper type has means for comparing a reference signal with a control signal varying with battery voltage, and terminating the charge when the rate of rise of battery voltage falls below a predetermined value. To prevent spurious operation due to mains voltage variation, the control signal comprises the difference between a signal dependent on battery voltage and a signal dependent on a.c. supply voltage. The rate of rise of the control signal is monitored by comparing it with a staircase reference voltage which is increased by a step whenever the control signal exceeds it, and termination is initiated if the time interval between two steps exceeds a given period. This may be long enough, e.g. half an hour, to provide an equalizing charge without requiring additional equipment.

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Bolton, United Kingdom

George W Foster