Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
1999-11-29
2001-10-16
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S128000
Reexamination Certificate
active
06304061
ABSTRACT:
This application is based on applications No. 10-340494 filed in Japan on Nov. 30, 1998 and No.11-232907 filed in Japan on Aug. 19, 1999, the contents of which are incorporated hereto by reference.
BACKGROUND OF THE INVENTION
This invention relates to a method of computing the capacity of a battery array made up of a plurality of rechargeable batteries connected in series, and controlling charging and discharging of the battery array.
A rechargeable battery capable of repeated charging and discharging is provided with a full charge detection circuit and an over-discharge protection circuit to prevent over-charging and over-discharging. As means of detecting whether a battery is fully charged, the voltage detection method which detects a rechargeable battery's voltage, the −DV method which detects a specified voltage drop from a peak rechargeable battery voltage, the temperature detection method which detects a rechargeable battery's temperature, and other methods are known. In addition, methods such as rechargeable battery voltage detection are widely known for incorporation into an over-discharge protection circuit.
Incidentally, in the use of rechargeable batteries as power sources, a plurality of rechargeable batteries are often electrically connected together in both series and parallel combinations for use as a battery array. In the case of a battery array, the capacity of each individual rechargeable battery and the performance of each rechargeable battery with charging and discharging shows some variation, and all rechargeable batteries do not react in exactly the same way. Consequently, even though observation of the over-all battery array shows no indication of a problem, it is possible that one part of the rechargeable battery array has over-charged or over-discharged and the battery array as a whole has been degraded.
To solve this problem, Japanese Patent Application HEI 7-335266 (1995) discloses a provision for bypass circuitry for each of a plurality of rechargeable batteries connected in series. However, for the case of a battery array used as a power source for an electric automobile, the number of rechargeable batteries connected in series is around two hundred, and circuit complexity becomes extreme.
Thus, it is an object of the present invention to provide a method of controlling charging and discharging of a battery array via a simple configuration that prevents over-charging and over-discharge of each component rechargeable battery of the battery array.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with a accompanying drawings.
SUMMARY OF THE INVENTION
The first embodiment of the present invention is a method of controlling the charging and discharging of a battery array while computing the capacity of the battery array which is made up of a plurality of rechargeable batteries connected in series. An upper capacity limit lower than the full charge capacity of the battery array, a lower capacity limit greater than the capacity at complete discharge, and a specified capacity in the range between the upper capacity limit and the lower capacity limit are established. When the computed capacity is within the range between the upper capacity limit and the lower capacity limit, battery array charging and discharging are allowed. When the computed capacity of the battery array reaches the upper capacity limit, only battery array discharging is permitted until the computed capacity becomes equal to the specified capacity. When the computed capacity of the battery array reaches the lower capacity limit, only battery array charging is permitted until the computed capacity becomes equal to the specified capacity.
In addition, the invention is characterized by revising battery array computed capacity when the computed capacity reaches the upper capacity limit or the lower capacity limit more than a specified number of times, or each time a specified time period has elapsed.
Revision of the computed capacity of the battery array is characterized by charging the battery array to a capacity tolerance limit lower than the full charge capacity, greater than the upper capacity limit, and reached when a battery temperature or a derivative of a temperature rise of at least one rechargeable battery of the battery array becomes equal to or greater than a specified value, or battery voltage becomes equal to or greater than a specified voltage. At that point, the capacity tolerance limit is written into the battery array computed capacity and subsequently, charging is prohibited until battery array computed capacity reaches the specified capacity.
The second embodiment of the present invention is a method of controlling the charging and discharging of a battery array while computing the capacity of the battery array which is made up of a plurality of rechargeable batteries connected in series. An upper capacity limit lower than the full charge capacity of the battery array, a lower capacity limit greater than the capacity at complete discharge, an a specified capacity in the range between the upper capacity limit and the lower capacity limit are established. When the computed capacity is within the range between the upper capacity limit and the lower capacity limit, battery array charging and discharging are allowed. When the computed capacity of the battery array reaches the upper capacity limit, only battery array discharge is permitted until the computed capacity becomes equal to the specified capacity. When the computed capacity of the battery array reaches the lower capacity limit, only battery array charging is permitted until the computed capacity becomes equal to the specified capacity, and battery array capacity computation is performed such that it is less than the computed battery array capacity. When a battery temperature or a derivative of a temperature rise of at least one rechargeable battery of the battery array becomes equal to or greater than a specified value during battery array charging, charging is suspended and a capacity tolerance limit lower than the full charge capacity and greater than the upper capacity limit is written into the computed battery array capacity.
After writing the capacity tolerance limit into the battery array capacity, battery array charging and discharging are allowed while the computed capacity is within range between the upper capacity limit and the lower capacity limit until the computed capacity of the battery array reaches the specified capacity. When the computed capacity of the battery array reaches the upper capacity limit, only battery array discharge is permitted until the computed capacity becomes equal to the specified capacity. When the computed capacity of the battery array reaches the lower capacity limit, only battery array charging is permitted until the computed capacity becomes equal to the specified capacity, and battery array computed capacity computation is performed such that it is greater than actual battery array capacity.
The third embodiment of the present invention is a method of controlling the charging and discharging of a battery array while computing the capacity of the battery array which is made up of a plurality of rechargeable batteries connected in series. An upper capacity limit lower than the full charge capacity of the battery array, a restricted charging capacity limit lower than the upper capacity limit for restricted charging, a lower capacity limit greater than the capacity at complete discharge, a restricted discharging capacity limit greater than the lower capacity limit for restricted discharging, and a specified capacity in the range between the restricted charging capacity limit for restricted charging and the restricted discharging capacity limit for restricted discharging are established. When the computed capacity is within the unrestricted region, battery array charging and discharging are allowed. When the computed capacity of the battery array is within the restricted charging region
Luk Lawrence
Sanyo Electric Co,. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
Wong Peter S.
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