Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2001-04-25
2002-07-23
Toatley, Gregory (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S160000
Reexamination Certificate
active
06424123
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a battery charging system, a charge control apparatus, and a charge control method for use in a computer, and particularly to a charging system for charging a rechargeable battery included in an intelligent battery, a charge control apparatus for controlling charge for a battery included in a power supply unit, a charge control method, and a computer employing the charge control method.
BACKGROUND OF THE INVENTION
As mobile computing has become pervasive, portable personal computers (hereinafter referred to as portable PCs) having various sizes and functions have been developed. For instance, they include notebook PC, sub-notebook PC, palmtop PC, and PDA (Personal Digital Assistant).
A portable PC includes an internal battery which is generally removable. This allows a user to operate the portable PC in an environment in which no commercial power supply is available, for instance, in a train. A secondary battery is usually employed s the internal battery which can be repeatedly used by charging.
Conventionally, to charge such a secondary battery, the charging voltage is set to the maximum allowable voltage of the battery to maximize the capacity at the beginning of using the battery (hereinafter referred to as “initial capacity”).
However, in the above described conventional technique in which the charging is carried out with the charging voltage set to the maximum voltage of the battery, there is a problem that the life of the battery is shorter than the case in which the charging is performed using a charging voltage lower than the allowable maximum voltage.
Also, the secondary battery is generally characterized in that the total capacity decreases as the discharging and charging are repeated. Further, the decrease in the total capacity is more noticeable as the charging voltage is higher.
FIG. 16
shows an example of the charging characteristics of a lithium-ion battery single cell having a voltage rating of 4.2 V, for charging voltages of 4.10 V and 4.20 V. The ordinate in this figure represents the percentage ratio of capacity to the initial capacity (hereinafter referred to a“capacity ratio”). Accordingly, although the capacity ratio associated with zero charging/discharging cycles is 100% for both charging voltages of 4.10 V and 4.20 V, the actual capacity is different for each charging voltage. Further, the above-described number of charging/discharging cycles means the number of times the discharging is performed until the battery capacity becomes 0% after the charging is performed from 0% to 100% of the battery capacity. As shown in the
FIG. 16
, the capacity ratio decreases as the number of charging/discharging cycles increases, and the decrease in the capacity ratio is greater for the higher charging voltage.
Accordingly, in the prior art in which charging is performed with the charging voltage set to the allowable maximum voltage of the battery, the battery life is shorter as compared with the case in which charging is performed with a charging voltage lower than the allowable maximum voltage.
SUMMARY OF THE INVENTION
The present invention seeks to solve the above problems, and has as its object the provision of a charging system which enables an increase in the initial capacity of a rechargeable battery whilst also prolonging the battery life.
In accordance with a charging system according to the present invention, a rechargeable battery included in an intelligent battery is charged by a charging device for which a charging condition can be set. The above battery may be any suitable battery type including: lithium-ion battery, nickel-hydrogen battery, nickel-cadmium battery, lithium-polymer battery, or equivalent.
The charging system of the present invention further includes a controller for receiving deterioration information related to the deterioration of the battery. The controller uses this deterioration information to set a charging condition of the charging device to increase battery capacity until the deterioration information meets a predetermined condition, and to set a different charging condition to increase battery life after the deterioration information meets the predetermined condition.
For instance, as a charging condition for increasing the battery capacity when a lithium-ion battery is used, the charging voltage is set to the allowable maximum voltage of the battery or to a predetermined voltage smaller but in the vicinity of the allowable maximum voltage, and similarly, as the charging condition for making the battery life longer, the charging voltage is set to a voltage lower than the charging voltage which is applied as the charging condition for increasing battery capacity.
The above-mentioned predetermined condition is used to indicate the timing for switching a charging condition from giving priority to a higher capacity to giving priority to a longer life. If, for instance, the user of the intelligent battery prefers a longer life to a higher capacity for the battery, a mode can be applied for setting the above predetermined condition to be met when the deterioration information indicates a lower degree of deterioration, and conversely, if the user prefers a higher capacity to a longer life for the battery, a mode can be applied for setting the above predetermined condition to be met when the deterioration information indicates a higher degree of deterioration. In this case, either the individual users may set the predetermined condition, or the predetermined condition may be set based on previous statistical examination of the intentions of users.
Further, regardless of the user's intention, for instance, the condition indicating the timing that can maximize the accumulated value of total capacities to the life of the battery provided in the intelligent battery related to the present invention (generally the period until the total capacity of a full-charged battery becomes 60% of the initial capacity) can be previously obtained by an experiment, computer simulation, or the like, and this condition can be applied as the above predetermined condition.
As described above, since the charging system of the present invention receives the deterioration information related to the deterioration of a battery from the intelligent battery, sets the charging condition of the charging device to make the battery capacity higher until the deterioration information meets a predetermined condition, and sets the charging condition to make the battery life longer after the deterioration information meets the predetermined condition, the initial capacity of the battery can be made larger and the life of the battery can be made longer.
The deterioration information of the charging system may be at least one of: the number of charging/discharging cycles of the battery, the capacity of the battery, and a value corresponding to the internal resistance of the battery.
That is, as described with reference to
FIG. 16
, since a rechargeable battery is generally characterized in that its total capacity decreases as the number of charging/discharging cycles increases, the number of charging/discharging cycles of the battery can be applied as information indicating the deterioration state of the battery. Further, any information that can provide the capacity of the battery can also be applied as information indicating the deterioration state of the battery. Furthermore, since a deteriorated battery usually tends to have an increase in internal impedance, the degree of deterioration of the battery can be determined based on a value corresponding to the internal resistance of the battery. Therefore, the value corresponding to the internal resistance of the battery can be applied as information indicating the deterioration state of the battery.
Further, if the number of charging/discharging cycles of the battery is included in the deterioration information, it can be assumed that the number of charging/discharging cycles is detected in a manner in which the charging amount or discharging amount of
Naitoh Arimasa
Odaohhara Shigefumi
LandOfFree
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