Abstract: A control circuit and method of operating a battery charging system are provided capable of disabling charging of a rechargeable battery (320) based upon a second derivative (410) of a temperature of the battery. A thermistor (330), contained in a rechargeable battery pack together with the rechargeable battery (320), detects the temperature of the battery. Charging of the battery can be disabled when the second derivative (410) of the temperature of the battery is positive and the first derivative (390) of the temperature of the battery is higher than a predetermined threshold.

Abstract: A method and apparatus for detecting the state of charge of a battery during charging or discharging thereof. Voltage levels across the battery are measured during battery charging or discharging, and compared with preset values representative of a normal battery characteristic charge or discharge curve. The normal charge or discharge curve is modified responsive particular battery characteristics indicated by measured battery voltage levels, and, preferably, also responsive to measured battery temperature levels to form a modified normal battery charge or discharge curve. The modified normal battery charge or discharge curve is divided into curve portions defined by voltage levels and rates of changes of the voltage levels. Each curve portion defines a particular state of charge of the battery.

Abstract: A battery charger for charging a nickel metal hydride battery with a fast charging current. The battery charger is operative to step-down, or constantly reduce, the magnitude of a charging current applied to a nickel metal hydride battery as the temperature level of the battery increases during charging thereof. As the temperature levels of the battery exceeds preset values, the magnitude of the charging current is reduced. When the temperature levels of the battery exceeds a maximum value, application of a fast charging current is terminated, and a trickle charging current is applied to the battery.

Abstract: A battery charging system for a multi-cell battery charger operative to apply a charging current to one or more battery packs, each comprised of one or more battery cells. Initiation of application of a fast charging current is permitted only when the voltage levels taken across output terminals of a battery pack positioned at the battery charger, and the ambient temperature of such battery pack, is within desired ranges. After initiation of application of the fast charging current, the ranges of voltage and ambient temperature levels within which application the fast charging current is permitted are expanded to prevent termination of application of the fast charging current responsive to transient changes of the temperature and voltage levels.

Abstract: A system and associated method for fast charging a battery. The current level of a fast charging curent supplied to a battery for the charging thereof is monitored. When the charging current falls below a predetermined level for a certain proportion of a time period, fast charging of the battery is terminated.

Abstract: A battery charging system for determining battery charge states of batteries positioned to be charged by a battery charger. A fast charging current is supplied for short intervals to each of the batteries during a charge state determination period. After the end of the charge state determination period, the battery charge states of each of the batteries is determined. The determined battery charge states may be utilized to form a battery charging priority sequence for sequentially charging the batteries.

Abstract: A unique automatic battery charger (100) is described that recharges a battery (202) including a thermistor (206) for sensing the battery temperature. The charger (100) produces both a slow-charge current and a fast-charge current. Upon detecting the presence of the battery (202), the unique charger (100) turns on a fast-charge current produced by a switchable current source (110-113). The fast-charge current is subsequently turned off when the battery (202) is fully charged as indicated by the status of monitored temperature and voltage conditions. Comparators (180-184) are utilized to monitor these voltage and temperature conditions. According to a novel feature of the present invention, the monitored temperature thresholds are changed in response to the supply voltage. The automatic battery charging apparatus of the present invention may be advantageously utilized in a variety of applications for rapidly and safely charging batteries used in battery-operated electrical apparatus.

Abstract: A wideband, modulation sensitivity compensated, voltage controlled oscillator which automatically and continuously compensates over a wide bandwidth for modulation sensitivity variations resulting from changes in the center frequency of oscillation. The invention includes a compensation network which continuously varies the coupling between the modulation circuit and the oscillator tank circuit in response to changes in the steering control signal applied to a steering network. Continuous modulation sensitivity compensation is thereby provided over a wide bandwidth.

Abstract: An exceptionally wideband, synthesizer controlled voltage controlled oscillator is disclosed which is characterized by a plurality of pin diode frequency shift networks which, when actuated shifts the frequency of the oscillator in selectable binary steps within a wide frequency range in the order of 48 MHz. Special means are included to prevent undesireable parasitic oscillation modes when such frequency shift networks are in an inactuated, switched off mode. A multiple varactor tuning circuit is provided for selecting a precise frequency within a relatively narrow frequency band on the order of 6 MHz.