Electricity: battery or capacitor charging or discharging – Battery or cell charging – With thermal condition detection
Reexamination Certificate
2000-05-26
2001-07-24
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
With thermal condition detection
C320S137000
Reexamination Certificate
active
06265850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for detecting abnormality in a parallel battery, and more specifically relates to a method for detecting abnormality in a parallel battery-connection circuit.
In this application, a plurality of secondary batteries connected in series is referred to as “a serial circuit,” and a circuit in which a plurality of serial circuits are connected in parallel is referred to as “a parallel battery-connection circuit”.
2. Description of the Related Art
In one use of secondary batteries, a plurality of secondary batteries are connected in series (serial circuit) so as to provide a high voltage, and a plurality of serial circuits are also connected in parallel so as to provide a high capacity. In order to detect a problem, e.g., an internal short-circuit occurring in such a secondary battery circuit, the following two methods have been proposed.
In one method, the voltage or current value in each serial circuit is monitored so as to compare voltages and current values between the serial circuits and detect a voltage drop or a current value rise caused by abnormality. A serial circuit may be divided into several blocks for a block-by-block complete monitoring. This method is, however, impractical because it requires a complicated apparatus, which may cause a high possibility of defects and dispersion in detected values.
The other method for detecting abnormality utilizes a current value rise of in a serial circuit including a secondary battery with a problem, e.g., overcharging or overdischarging. Specifically, the temperature of a serial circuit rises when the circuit includes a secondary battery with such a problem. Therefore, the abnormality detection in a parallel battery-connection circuit can be controlled based on the absolute value of the temperature values detected from the plurality of serial circuits.
However, the following problem arises if the abnormality detection in a parallel battery-connection circuit is controlled based on the absolute value of the temperature values detected from the plurality of serial circuits.
The temperature values of a plurality of serial circuits are prone to be affected by the environmental temperature outside the parallel battery-connection circuit. If the environmental temperature outside the parallel battery-connection circuit is high, the temperature values of the plurality of serial circuits will also become high.
Therefore, in the case where the environmental temperature outside the circuit is high, the temperature values detected from the serial circuits would rise even if there is no problem of overcharging or overdischarging the secondary batteries of the parallel battery-connection circuit. As a result, such a method of abnormality detection has a risk of resulting in an erroneous determination that an abnormality has been generated even if there is no problem in the parallel battery-connection circuit.
SUMMARY OF THE INVENTION
In the method for detecting abnormality in a parallel battery-connection circuit of this invention, the parallel battery-connection circuit includes: a first circuit including a first plurality of batteries connected in series and a second circuit including a second plurality of batteries connected in series; wherein: at least one of the first plurality of batteries is connected to a first temperature detection section, at lest one of the second plurality of batteries is connected to a second temperature detection section, and the first temperature detection section and the second temperature detection section are connected to an abnormality determining section for determining abnormality in the parallel battery-connection circuit, the method including the steps of: detecting a first temperature of the at least one of the first plurality of batteries by the first temperature detection section; detecting a second temperature of the at least one of the second plurality of batteries by the second temperature detection section; and determining abnormality in the parallel battery-connection circuit by the abnormality determining section based on a temperature difference between the first temperature detected by the first temperature detection section and the second temperature detected by the second temperature detection section.
In one embodiment of the invention, the step for determining abnormality may further include the step of determining that the parallel battery-connection circuit has abnormality when the temperature difference exceeds a certain value.
In another embodiment of the invention, the step for determining abnormality may further include the step of determining, in the case where the temperature difference exceeds the certain value, that there is an abnormal battery in the first circuit if the first temperature is higher than the second temperature, or that there is an abnormal battery in the second circuit if the second temperature is higher than the first temperature.
In still another embodiment of the invention, another one of the first plurality of batteries may be connected to a third temperature detection section, another one of the second plurality of batteries may be connected to a fourth temperature detection section, and the third temperature detection section and the fourth temperature detection section may be connected to the abnormality determining section for determining abnormality in the parallel battery-connection circuit, the method further including the steps of: detecting a third temperature of another one of the first plurality of batteries by the third temperature detection section; detecting a fourth temperature of another one of the second plurality of batteries by the fourth temperature detection section; and determining abnormality in the parallel battery-connection circuit by the abnormality determining section based on a temperature difference between the third temperature detected by the third temperature detection section and the fourth temperature detected by the fourth temperature detection section.
In another aspect of the invention, an abnormality detection apparatus for a parallel battery-connection circuit is connected to the parallel battery-connection circuit including: a first circuit including a plurality of first batteries connected in series; and a second circuit including a plurality of second batteries connected in series, the abnormality detection apparatus including: a first temperature detection section connected to at least one battery of the first circuit; a second temperature detection section connected to at least one battery of the second circuit; and an abnormality determining section connected to the first temperature detection section and the second temperature detection section, the abnormality determining section determining abnormality of the parallel battery-connection circuit, based on the temperature difference between the first temperature detected by the first temperature detection section and the second temperature detected by the second temperature detection section.
In one embodiment of the invention, the abnormality determining section may determine that the parallel battery-connection circuit is abnormal when the temperature difference exceeds a certain value.
In another embodiment of the invention, the abnormality determining section may determine, in the case where the temperature difference exceeds the certain value, that there is an abnormal battery in the first circuit if the first temperature is higher than the second temperature, or that there is an abnormal battery in the second circuit if the second temperature is higher than the first temperature.
In still another embodiment of the invention, at least one of the first plurality of batteries or the second plurality of batteries may include a nickel metal hydride battery.
In still another embodiment of the invention, the abnormality detection apparatus may further include a third temperature detection section connected to another battery of the first circuit and a fourth temperature
Hayashi Takayuki
Kimura Tadao
Luk Lawrence
Matsushita Electric - Industrial Co., Ltd.
Renner , Otto, Boisselle & Sklar, LLP
Wong Peter S.
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