Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Patent
1990-07-06
1992-12-29
Hickey, R. J.
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
322 33, 322 73, 322 28, 320 35, 320 46, H02J 714
Patent
active
051754860
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a dual-level output circuit, for example of the type used to control the charging of a motor-vehicle battery. DE-A-3041200 discloses a controller in which the charging current supplied to a battery depends upon the state of charge of the battery, i.e. whether it is substantially fully charged. There is danger of excess gassing if a high charging current is supplied to a battery which is already full-charged.
According to a first aspect of the present invention there is provided a circuit having an input and an output which can deliver at least two distinct output levels depending upon the level of a signal applied to the input, characterised in that the circuit comprises at least two independently variable resistors and switch means connected thereto and responsive to the input signal, whereby the output levels may be adjusted to independent values.
An advantage of the above-described circuit is that it may be readily adjusted for different specific applications. For example, even batteries of the same type have different charging characteristics. Also, the characteristics of a single battery vary with age and it is an advantage to be able to adjust independently the high and low charging rates (corresponding to a substantially flat and a substantially fully-charged battery).
In a preferred arrangement the variable resistors R1,R2 are connected in parallel and the switch means comprises first switch device T1 in series with the first variable resistor and a second switch device T2 in series with the second variable resistor. This has the advantage that the adjustment of the output levels is completely independent.
The switch means is preferably one or more transistors. This has the advantage of providing an arrangement suitable for gradual rather than instantaneous switching-over.
The circuit may receive its input signal from means responsive to the charge of the battery in the form of a hydrogen and oxygen recombinator and a transducer responsive to the temperature thereof. The transducer output may be connected to the circuit input via an integrator to ensure a gradual operation of the switch means. This has the advantage of reducing abrupt voltage fluctuations which, when charging a motor vehicle battery, can cause unwanted dimming and brightening of the vehicle lights. In an alternative arrangement the circuit receives its input signal from a device sensitive to gas pressure within the battery.
According to a second aspect of the present invention, there is provided a battery-charging arrangement comprising a voltage controller responsive to means for producing an input signal S which can have at least two distinct levels characterised in that said means comprises means for producing an output signal W which changes relatively abruptly when the battery charge reaches a predetermined level, means for receiving said signal and producing therefrom a relatively-gradually changing signal X, which is used to produce said distinct levels.
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which:
FIG. 1 is a circuit diagram of a first embodiment of the present invention used as in input stage to a voltage control circuit;
FIG. 2 is a similar circuit diagram of a second embodiment of the present invention;
FIG. 3 shows a voltage control circuit with which the circuits of FIGS. 1 and 2 may be used, the voltage control circuit controlling the voltage supplied by a generator to a motor-vehicle battery; and
FIG. 4 shows a suitable circuit for supplying an input signal W to the circuits of FIGS. 1 and 2.
Referring to the drawings, FIG. 1 shows a circuit 10 connected as an input stage to a controller 11. The circuit is arranged to receive a varying input signal X, discussed below in connection with FIG. 4, which is applied to the base of a transistor T. The emitter of transistor T is connected to ground via a first variable resistor R1. The collector of transistor T is connected to the input of
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patent: 4136311 (1979-01-01), Scheidler
patent: 4310793 (1982-01-01), Sheldrake et al.
patent: 4384245 (1983-05-01), Metter
patent: 4689545 (1987-08-01), Komurasaki et al.
Hickey R. J.
Robert & Bosch GmbH
Striker Michael J.
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