Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2001-05-23
2003-05-13
Tso, Edward H. (Department: 2838)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
C320S132000
Reexamination Certificate
active
06563318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a detecting method for detecting internal state of a rechargeable battery and a detecting device suitable for practicing said detecting method. The internal state here is meant to include deterioration state, remaining capacity (=presently stored electricity quantity=dischargeable capacity), usable capacity (=presently residual electricity quantity which is still able to operate an instrument), charging capacity, electricity storable capacity, and internal resistance of said rechargeable battery. The present invention also relates an instrument provided with said detecting device. The present invention includes a program of detecting said internal state of said rechargeable battery and a medium having said program accommodated therein which are available in said detecting method and said detecting device.
2. Prior Art
In recent years, along with development of semiconductor elements and development of miniature, light-weight and high performance rechargeable batteries, mobile instruments such as portable personal computers, video cameras, digital cameras, cellular phones, and personal digital assistants including palmtop PCs have been rapidly progressed.
Separately, in recent years, the global warming of the earth because of the so-called greenhouse effect to an increase in the content of CO
2
gas in the air has been predicted. For instance, in thermal electric power plants, thermal energy obtained by burning a fossil fuel is converted into electric energy, and along with burning of such fossil fuel, a large amount of CO
2
gas is exhausted in the air. Accordingly, in order to suppress this situation, there is a tendency of prohibiting to newly establish a thermal electric power plant. Under these circumstances, so-called load leveling practice has been proposed in order to effectively utilize electric powers generated by power generators in thermal electric power plants or the like, wherein using a load conditioner having a rechargeable battery installed therein, a surplus power unused in the night is stored in rechargeable batteries installed at general houses and the power thus stored is used in the daytime when the demand for power is increased, whereby the power consumption is leveled.
Separately, in recent years, electric vehicles comprising a rechargeable battery and which do not exhaust any polluting substances have been proposed. Besides hybrid powered automobiles in which a combination of a rechargeable battery and an internal combustion engine or a fuel cell is used and the fuel efficiency is heightened while restraining exhaustion of polluting substances have been also proposed. As the rechargeable battery used in these electric vehicles and hybrid powered automobiles, a high performance rechargeable battery having a high energy density is expected to be developed.
Such rechargeable battery used in the mobile instrument, the load conditioner used for practicing the load leveling, the electric vehicle and the hybrid powered automobile typically includes a rechargeable lithium battery (including a lithium ion battery) in which reduction-oxidation reaction of lithium is used, a nickel-hydride rechargeable battery, a nickel-cadmium rechargeable battery, and a lead rechargeable battery.
Incidentally, in each of the mobile instrument, the load conditioner in the load leveling, the electric vehicle and the hybrid powered automobile, it is important to be able to precisely detect the dischargeable capacity (the remaining capacity), the usable capacity and the lifetime of the rechargeable battery in order to prevent the operation of the mobile instrument, the load conditioner, the electric vehicle or the hybrid powered automobile from being suddenly stopped.
In order to detect the usable capacity of a rechargeable battery, there is known a method wherein the voltage of the battery is measured and based on the measured result, the usable capacity is estimated.
The term “remaining capacity” of the rechargeable battery is meant a presently stored electricity quantity which can be discharged.
The term “usable capacity” is meant a presently residual electricity quantity of the rechargeable battery with which an instrument (or apparatus) having said rechargeable battery can be still operated. The usable capacity is included in the term remaining capacity.
Aforesaid method is applicable in the case of a lithium ion rechargeable battery whose anode material comprising a carbonous material difficult to convert into a graphite and which is distinguished from a graphite, because the battery voltage is gradually decreased in proportion to the quantity for the electricity to be discharged, and therefore, the presently residual electricity quantity can be detected by measuring the battery voltage. However, the method is not always applicable in other rechargeable batteries whose battery voltage is not gradually decreased in proportion to the quantity for the electricity to be discharged as in the case of the lithium ion rechargeable battery (whose anode comprising a graphite), where it is difficult to precisely detect the remaining capacity for the reason that the battery voltage is varied depending on the electric current flown and it is not proportional to the quantity for the electricity to be discharged. Besides, in the case of a rechargeable battery whose performance has been deteriorated to close its lifetime, it is extremely difficult to detect the remaining capacity. Separately, in the case of a lithium ion rechargeable battery whose anode material comprising a graphite series carbonous material, because the battery voltage with respect to the quantity for the electricity to be discharged is flat, the remaining capacity is difficult to obtain from the battery voltage in accordance with the foregoing method.
There is known other method in order to detect the remaining capacity of a rechargeable battery, wherein a cumulative discharged-electricity quantity is memorized and the cummulative discharged-electricity quantity is subtracted from a charged-electricity quantity to obtain a presently residual electricity quantity (that is, a remaining capacity). However, this method has such disadvantages as will be described in the following. That is, the current value and the discharge time are necessary to be always memorized. Besides, in the case where additional charging is performed for the rechargeable battery which is unknown with respect to the discharge depth, although the charged-electricity quantity at that time can be detected, the remaining capacity of the rechargeable battery after the rechargeable battery is subjected to charging cannot be precisely detected because the remaining capacity of the rechargeable battery before the additional charging is unknown. When the method is adopted in this case, because the method is to obtain a remaining capacity by comparing the cumulative discharged-electricity quantity with the remaining capacity prior to the discharging, a large error is likely to occur in the measurement.
Therefore, the method is difficult to cope with a rechargeable battery whose performance has been deteriorated to close its lifetime, where it is difficult to precisely detect the remaining capacity.
Now, Japanese Unexamined Patent Publication No. 2066/1992 discloses a method for observing the capacity of a lead battery in accordance with recovery characteristic of the battery voltage after pulse discharge. Japanese Unexamined Patent Publication No. 136774/1992 discloses a method wherein for a rechargeable battery, when the power source is ON, discharging is temporarily performed at a large current to detect a decrease in the battery voltage, the detected decrease value is compared with a prejudged battery voltage value, where when the difference is great, the residual capacity is judged to be insufficient. Japanese Unexamined Patent Publication No. 16607/1999 discloses a method wherein for a rechargeable battery, the battery voltage when a prescribed curren
Degura Yasusaburo
Kawakami Soichiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Tso Edward H.
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