Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2001-01-31
2001-10-02
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C324S434000
Reexamination Certificate
active
06297618
ABSTRACT:
BACKGROUND OF THE INVENTION
A prior art power storage device is disclosed in Japanese Patent Laid-open No. Hei 8-78060(1996). In this power storage device, two storage battery units are connected in series, and a voltage determining device and a plurality of series-connected resistors are connected across the opposite ends of each of the storage battery units. The voltage determining device provides a voltage indicating whether or not the voltage of the storage battery unit is as high as a predetermined voltage. The series-connected resistors divide the voltage of the storage battery unit to provide a reference voltage.
A comparator compares the output voltage of the voltage determining device with the reference voltage determined by resistance type voltage division. If one of the storage battery units is fully charged and the output voltage of the voltage determining device is higher than the reference voltage, the output of the comparator goes LOW. Then, a FET connected in series to the storage battery unit is turned off to stop charging the storage battery unit.
In this prior art power storage device, the potential levels of the output of the voltage determining devices with respect to the potential level of the lowest negative terminal of the series-connected storage battery units are different. Therefore, the series-connected resistors for determining the reference voltage must be specially formed for the storage battery units. Thus, circuits of the same function conforming to the potential levels of the storage battery units are necessary for the storage battery units.
Since the resistances of the resistors are dispersed in a range around a nominal resistance, the reference voltages indicating a fully charged state differ from each other and the accuracy of the reference voltages is unsatisfactory. Therefore, resistors having resistances close to a desired resistance must be selectively used. Such resistors, however, are expensive.
The withstand voltage of the comparator must be equal to the sum of the voltages of the series-connected storage battery units. Therefore, when many storage battery units are connected in series, an increased number of circuits respectively conforming to the potential levels of those storage battery units are necessary, which increases the cost, size and power consumption of the power storage device and the power storage device needs parts including a comparator having a high withstand voltage.
SUMMARY OF THE INVENTION
A power storage device according to the present invention comprises: a plurality of series-connected storage battery units; a plurality of battery circuits that provides signals of potential levels respectively corresponding to the voltages of the storage battery units; and a plurality of potential level changing circuits for changing the potential levels of the output signals of the battery circuits. The output signals of the potential level changing circuits are given to a signal processing circuit. The signal processing circuit carries out predetermined processes on the basis of input signals or produces a control signal for controlling the storage battery units. The output control signal of the signal processing circuit changes potential levels in the potential level changing circuits and is given to the plurality of battery circuits. The battery circuits control the storage battery units on the basis of the input control signal so that the voltages of the storage battery units are equalized by, for example, bypass circuits. According to the present invention, the signal processing circuit is able to process a plurality of voltage measurement signals through potential level conversion, so that the number of the component parts of the power storage device can be reduced.
The potential level changing circuit of the power storage device according to the present invention is a circuit provided with an insulating coupler interposed between the battery circuits and the signal processing circuit or a level shift circuit. The signal processing circuit of the power storage device according to the present invention is a processor, such as a microcomputer, or a controller.
In the power storage device according to the present invention, an error in measurement included in a power storage unit voltage measured by the storage circuit and caused due to the variation of the element is correction-calculated by the data processing circuit.
In the power storage device according to the present invention, the battery circuits provides pulse signals respectively corresponding to the storage battery units. The potential level of each pulse signal is changed by the potential level changing circuit. The pulse signals are digital signals or differential pulse signals. Use of the pulse signals reduces errors in voltage measurement due potential level change. The pulse signal is a pulse signal of a pulse width corresponding to the voltage of the storage battery unit or a pulse train continuous for a time period corresponding to the voltage of the storage battery unit. Conversion of the voltage of the storage battery unit, which is an analog value, into a pulse signal improves the accuracy of voltage measurement. The conversion of the voltage into the pulse signal can be achieved by various method, such as a method using hardware, such as a circuit and a method using software, such as a microcomputer.
The power storage device according to the present invention is applied to various storage battery units capable of an electric power storage function, such as secondary battery units including lithium battery units and nickel-hydrogen battery units, and electric double layer capacitors, and to a device formed by connecting storage battery units in series. The power storage device according to the present invention is applied to various storage battery systems, such as a storage battery system formed by connecting in series a plurality of storage battery groups each formed by connecting a plurality of storage battery units in series or in parallel.
REFERENCES:
patent: 5710506 (1998-01-01), Broell et al.
patent: 5955869 (1999-09-01), Rathmann
patent: 6043631 (2000-03-01), Tsenter
Akiyama Noboru
Emori Akihiko
Kinoshita Takuya
Kojima Yasuyuki
Miyazaki Hideki
Hitachi , Ltd.
Hogan & Hartson L.L.P.
Tso Edward H.
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