Method of controlling charging and discharging

Details Method of controlling charging and discharging Method of controlling charging and discharging

1999-11-29

2001-05-29

Wong, Peter S. (Department: 2838)

Electricity: battery or capacitor charging or discharging

Battery or cell charging

With detection of current or voltage integral

C320S137000

Reexamination Certificate

active

06239580

ABSTRACT:

This application is based on application No. 10-341856 filed in Japan on Dec. 1, 1998, the content of which is incorporated hereinto 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 series connected rechargeable batteries, and controlling charging and discharging of that 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-discharge. As a means of detecting full charge, the voltage detection method which detects rechargeable battery voltage, the -DV method which detects a specified voltage drop from peak rechargeable battery voltage, the temperature detection method which detects rechargeable battery temperature, and other methods are known. On the other hand, 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 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 show some variation, and all rechargeable batteries do not result in exactly the same state. 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 components has over-charged or over-discharged and the battery array as a whole has been degraded.
To solve this problem, Japanese Non-examined Patent Publication No. 7-335266 issued on Dec. 22, 1995 discloses the provision of 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 accompanying drawings.
SUMMARY OF THE INVENTION
The method of controlling charging and discharging of the present invention controls charging and discharging of a battery array made up of a plurality of series connected rechargeable batteries while computing battery array capacity. The method of the present invention computes an integrated charge-discharge capacity during each period of a specified time interval. In addition, it performs forced charging or forced discharge of the battery array to make the sum of the integrated charge-discharge capacity during a second specified time interval plus that of a preceding first time interval approach zero.
In the charging and discharging of a battery array made up of a plurality of series connected rechargeable batteries, this method enables charging and discharging of the battery array while reliably preventing over-charging and over-discharge of all component rechargeable batteries regardless of capacity and performance variations of each component rechargeable battery.
Further, it is preferable to establish 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. 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, battery array computed capacity is revised.
Preferably, in the method of controlling charging and discharging of the present invention, battery array computed capacity is revised by charging until the temperature or the rate of the temperature rise of at least one rechargeable battery becomes equal to or greater than a specified value, or battery voltage becomes equal to or greater than a specified voltage. At that point, a capacity tolerance limit lower than the full charge capacity but greater than the upper capacity limit is written into the battery array computed capacity.
It is also preferable in the method of controlling charging and discharging of the present invention to prohibit battery array charging after computed capacity revision until battery array computed capacity reaches the specified capacity.


REFERENCES:
patent: 5545969 (1996-08-01), Hasegawa
patent: 5644212 (1997-07-01), Takahashi
patent: 6054840 (2000-04-01), Nakanishi et al.
patent: 3832839 (1990-03-01), None
patent: 19541959 (1996-05-01), None
patent: 7-335266 (1995-12-01), None

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