Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2002-09-13
2003-08-26
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
Reexamination Certificate
active
06611128
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery control device for controlling charging and discharging operations with respect to battery packs including alkaline storage batteries and mounted on, for example, devices driven by battery packs, such as electric vehicles including automated guided vehicles.
2. Description of the Related Art
Conventionally, as a low-pollution vehicle designed for the purpose of solving environmental problems and energy problems, an electric vehicle such as a HEV (hybrid electric vehicle) and a PEV (pure electric vehicle) has received a great deal of attention. The electric vehicle has a battery pack, which includes alkaline storage batteries, mounted therein, and the electric power of the battery pack drives an electric motor so as to run the electric vehicle.
The electric vehicle includes an inverter for controlling motor drive and a battery control device for obtaining an output state of the battery pack and controlling charging and discharging operations with respect to the battery pack according to the output state of the battery, pack, so as to stably supply the electric power to the electric motor via the inverter.
Such a conventional battery control device measures voltage and current output by the battery pack so as to calculate a remaining capacity SOC (State Of Charge; a value representing how much electric power remains in the battery pack) of the battery pack based on the measurement results. For example, the conventional battery control device controls the charge and discharge operations with respect to the battery pack so as to keep the remaining capacity SOC of the battery pack within a prescribed range. When the remaining capacity SOC falls below the prescribed range, the conventional battery control device performs a charging operation on the battery pack while inhibiting a discharging operation.
The battery pack as described herein includes a plurality of serially-connected battery blocks. In the case where the conventional battery control device charges the battery pack so as to keep the remaining capacity SOC of the battery pack within a prescribed range, when the plurality of battery blocks are uneven in remaining capacity SOC, some battery blocks are forced to be overcharged. Alternatively, in some cases, the conventional battery control device periodically overcharges the entire battery pack so as to realize evenness in state of charge between the plurality of battery blocks.
However, in the conventional battery control device, when a minute crack and/or a minute pinhole are/is made in a single alkaline storage battery included in the battery pack through long-time use, such a minute crack and/or a minute pinhole cannot be easily detected. When an alkaline storage battery is overcharged, water in an electrolyte contained in a unit-battery case of the single alkaline storage battery is electrolyzed, so that hydrogen and oxygen gasses are generated. Further, when the hydrogen gas is emitted through the minute crack and/or the minute pinhole to the outside of the single alkaline storage battery, the amount of the emitted hydrogen gas is small and the hydrogen gas is diffused due to cooling air from a battery cooling fan, thereby making it difficult to detect the minute crack and/or the minute pinhole in a unit battery.
Furthermore, when the unit battery is left with the minute crack and/or the minute pinhole, battery deterioration is accelerated, thereby significantly reducing the reliability of the battery pack. Examples of the battery deterioration include a rise in internal resistance due to loss in moisture content of the electrolyte or due to carbon dioxide absorbed into the electrolyte, a decrease in remaining capacity SOC due to hydrogen emitted from the unit-battery case (in the case where nickel-metal hydride batteries are used in place of the alkaline storage batteries), erosion of a negative electrode, etc.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a battery control device for controlling input to and output from a battery pack, in which the battery pack includes a plurality of serially-connected battery blocks each including a plurality of serially-connected unit batteries, and the device includes: an internal resistance measurement section for each battery block; and a first malfunctioning battery detection section for detecting the unit battery as a leakage malfunctioning battery based on an internal resistance variation measured for each battery block during a prescribed time interval of a charging operation, wherein detection information about the leakage malfunctioning battery is reflected in the control of charging and discharging operations.
According to this structure, the first malfunctioning battery detection section detects a unit battery as a leakage malfunctioning battery based on internal resistance variation and detection information about the leakage malfunctioning battery is reflected in the control of the charge and discharge operations. Therefore, a battery block which includes a unit battery having a minute crack and/or a minute pinhole can be detected early enough, thereby preventing the reliability of a battery pack from being reduced.
In one embodiment of the invention, the first malfunctioning battery detection section determines that the unit battery is a leakage malfunctioning battery when a difference in internal resistance variation between the unit battery and a normal battery is greater than a constant obtained based on battery characteristics, and the internal resistance variation is an internal resistance difference, or a difference in internal resistance derivative value, measured during a prescribed time period.
According to this structure, a leakage malfunctioning battery can be precisely and readily detected.
According to another aspect of the present invention, there is provided a battery control device for controlling input to and output from a battery pack, in which the battery pack includes a plurality of serially-connected battery blocks each including a plurality of serially-connected unit batteries, and the device includes: a battery voltage measurement section for each battery block; and a second malfunctioning battery detection section for detecting the unit battery as a leakage malfunctioning battery based on a battery voltage variation measured for each battery block during a prescribed time interval of an overcharging operation, wherein detection information about the leakage malfunctioning battery is reflected in the control of charging and discharging operations.
According to this structure, the second malfunctioning battery detection section detects a unit battery as a leakage malfunctioning battery based on battery voltage variation and detection information about the leakage malfunctioning battery is reflected in the control of the charge and discharge operations. Therefore, a battery block which includes a unit battery having a minute crack and/or a minute pinhole can be detected early enough, thereby preventing the reliability of a battery pack from being reduced.
In one embodiment of the invention, the second malfunctioning battery detection section determines that the unit battery is a leakage malfunctioning battery when a difference in voltage variation between the unit battery and a normal battery is greater than a constant obtained based on battery characteristics, and the voltage variation is a voltage difference, or a difference in voltage derivative value, measured during a prescribed time period.
According to this structure, a leakage malfunctioning battery can be precisely and readily detected.
In one embodiment of the invention, the battery control device further includes a third malfunctioning battery detection section for detecting the unit battery as a leakage malfunctioning battery based on a battery temperature variation measured for each battery block during a prescribed time interval of the overcharging operation.
According to this structure, a
Minamiura Keiichi
Nakanishi Toshiaki
Snell & Wilmer LLP
Tibbits Pia
Tso Edward H.
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