Electricity: battery or capacitor charging or discharging – Diverse charging or discharging rates for plural batteries
Reexamination Certificate
2002-12-27
2004-08-03
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Diverse charging or discharging rates for plural batteries
C320S160000
Reexamination Certificate
active
06771046
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present nonprovisional application claims priority under 35 USC 119 to Japanese Patent Application No. 2002-003616 filed on Jan. 10, 2002; Japanese Patent Application No. 2002-008962 filed on Jan. 17, 2002 and Japanese Patent Application No. 2002-008964 filed on Jan. 17, 2002 the entire contents thereof are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and a system for controlling the charging of a secondary battery, and particularly to a method of and a system for controlling the charging of a secondary battery, which are suitable for enhancing the durability of the secondary battery, that is, keeping the initial charging/discharging performance of the secondary battery for a long-period of time.
2. Description of Background Art
In the case of charging a secondary battery using nickel oxide as the material of a cathode (positive electrode), for example, a nickel-cadmium battery or a nickel-hydrogen battery, as the battery is charged to a full-charge level, oxygen gas is generated at the positive electrode. If the generation of the oxygen gas is continued, the inner pressure of the secondary battery is raised. Accordingly, the oxygen gas thus generated is required to be consumed by local cell reaction on the surface of an anode (negative electrode). In general, taking into account the gradual reduction in capacity of the negative electrode by the local cell reaction, the capacity of the negative electrode is set to be larger than that of the positive electrode. For example, a ratio (NP ratio) of the capacity of the negative electrode to that of the positive electrode is set to a value in a range of about 1.65 to 2.0. However, since the charging capacity of the battery is increased with the positive electrode taken as a rate-limiting factor, the increased capacity of the negative electrode brings enlargement of the secondary battery but does not contribute to an increase in charging capacity of the battery.
A charging method capable of suppressing the generation of oxygen gas by stopping the charging at a charge level less than a full-charge level, for example, 97% of the full-charge level has been proposed in Japanese Patent Laid-open No. Hei 5-111175. This charging method is advantageous in that since the generation of oxygen gas is suppressed, the reduction in capacity of a negative electrode by local cell reaction can be prevented, with a result that it is possible to reduce the capacity of the negative electrode, and hence to miniaturize the secondary battery, that is, increase the charging capacity.
The charging control to stop the charging at a charge level less than a full-charge level as described above is preferable from the viewpoint of the durability of a secondary battery; however, if the charging is usually stopped at a charge level less than the full-charge level, a state wherein several percent of electrode plates are not used is repeated. As a result, the unused electrode plates are deteriorated, which do not contribute to the charge amount.
By setting a voltage reference value (cut-off voltage) representative of a reference charge amount at which the charging is to be stopped, at a level as close to a full-charge level as possible, it is possible to reduce the number of the electrode plates not contributing to the charge amount. However, since the voltage of a secondary battery is dependent on a battery temperature and an environmental temperature, it is not easy to accurately detect that the voltage of the secondary battery reaches the cut-off voltage, and therefore, it is not expected to accurately control the charging of the secondary battery.
SUMMARY AND OBJECTS OF THE INVENTION
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a method of and a system for controlling the charging of a secondary battery, which are capable of preventing a reduction in full-charge amount due to repetition of the changing at a charge level less than the full-charge level.
It may be considered to periodically charging the secondary battery at a charge level more than the full-charge level. However, if the charging of the battery to a charge level more than the full-charge level is simply performed as conventional, there may occur a difference between the charging of the battery to a charge level less than the full-charge level and the charging of the battery to a charge level more than the full-charge level. Such a difference in charging time therebetween gives an unfavorable feeling to a user.
In view of the foregoing, the present invention provides a method of and a system for controlling the charging of a secondary battery, which are capable of preventing a reduction in a full-charge amount due to repetition of the changing at a charge level less than the full-charge level, and performing a simple control by means of which the charging time is usually kept nearly constant.
To achieve the above object, the present invention provides a method of controlling the charging of a secondary battery, including the steps of: controlling the charging of the secondary battery by using both a first charging control specified to stop the charging at a charge level less than a full-charge level and a second charging control specified to stop the charging at a charge level equal to or more than the full-charge level; wherein after the charging by the first charging control is continuously repeated by a specific number of times, the next charging is performed by the second charging control and if the state of the secondary battery satisfies a specific refresh discharge reference in the second charging control, the secondary battery is discharged before the charging of the secondary battery.
According to a second feature of the present invention, there is provided a system for controlling the charging of a secondary battery, including: first charging control means for stopping the charging at a charge level less than a full-charge level; second charging control means for stopping the charging at a charge level equal to or more than the full-charge level and deciding means for deciding that the charging by the first charging control means is continuously repeated by a specific number of times. A control means switching means is provided for switching, if it is decided by the deciding means that the charging by the first charging control means is continuously repeated by the specific number of times, the first charging control means to the second charging control means so as to perform the next charging by the second charging control means.
According to another feature of the present invention, there is provided a system for controlling the charging of a secondary battery, including: first charging control means for stopping the charging at a charge level less than a full-charge level; second charging control means for stopping the charging at a charge level equal to or more than the full-charge level and a random number generating means for generating a random number each time one charging by the first charging control means is performed. A control means switching means is provided for switching, if the random number generated by the random number generating means corresponds to a specific value equal to or less than the maximum value among the generated random numbers, the first charging control means to the second charging control means so as to perform the next charging by the second charging control means.
According to another feature of the present invention, the above control means switching means is configured such that the specific number of times of the repeated charging by the first charging control becomes less than 20.
According to a further feature of the present invention, the battery capacity, less than the full-charge level, at which the charging by the first charging control means is to be stopped, is composed of two-step battery capacities. A selecting means is provided for select
Ariga Kyoichi
Sone Takashi
Honda Giken Kogyo Kabushiki Kaisha
Tso Edward H.
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