Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells – With discharge of cells or batteries
Reexamination Certificate
2000-09-11
2001-08-14
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
With discharge of cells or batteries
C320S116000
Reexamination Certificate
active
06275004
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a battery pack operating in a hybrid-electric powertrain for a vehicle. More specifically, the present invention relates to a method and apparatus to control at least one voltage output of a DC—DC converter to regulate the charge of individual battery modules of the battery pack.
BACKGROUND OF THE INVENTION
In today's automotive market there exist a variety of propulsion or drive technologies used to power vehicles. The technologies include internal combustion engines (ICEs), electric drive systems utilizing batteries and/or fuel cells as an energy source, and hybrid systems utilizing a combination of internal combustion engines and electric drive systems. The propulsion systems each have specific technological, financial, and performance advantages and disadvantages, depending on the state of energy prices, energy infrastructure developments, environmental laws, and government incentives.
The increasing demand to improve fuel economy and reduce emissions in present vehicles has led to the development of advanced hybrid vehicles. Hybrid vehicles are classified as vehicles having at least two separate power sources, typically an internal combustion engine and an electric traction motor. Hybrid vehicles, as compared to standard vehicles driven by an ICE, have improved fuel economy and reduced emissions. During varying driving conditions hybrid vehicles will alternate between separate power sources, depending on the most efficient manner of operation of each power source. For example, a hybrid vehicle equipped with an ICE and an electric motor will shut down the ICE during a stopped or idle condition, allowing the electric motor to propel the vehicle and eventually restart the ICE, improving fuel economy for the hybrid vehicle.
Hybrid vehicles are broadly classified into series or parallel drivetrains, depending upon the configuration of the drivetrains. In a series drivetrain utilizing an ICE and an electric traction motor, only the electric motor drives the wheels of a vehicle. The ICE converts a fuel source to mechanical energy to turn a generator which converts the mechanical energy to electrical energy to drive the electric motor. In a parallel hybrid drivetrain system, two power sources such as an ICE and an electric traction motor operate in parallel to propel a vehicle. Generally, a hybrid vehicle having a parallel drivetrain combines the power and range advantages of a conventional ICE with the efficiency and electrical regeneration capability of an electric motor to increase fuel economy and lower emissions, as compared with a traditional ICE vehicle.
SUMMARY OF THE INVENTION
The present invention includes a vehicle having a parallel hybrid drive system incorporating an ICE and an electric motor generator (MoGen). The MoGen provides for propulsion of the vehicle during certain vehicle operating conditions, replaces an alternator to charge a battery pack in the vehicle, and replaces a conventional starter motor to start the ICE. The hybrid drive system of the present invention will utilize the ICE and MoGen to propel or motor the vehicle during the vehicle conditions which are most efficient for the ICE or MoGen operation. For example, during deceleration or a stopped condition, fuel flow to the ICE will be cut off, as these conditions are some of the least efficient conditions to run the ICE. The MoGen system becomes the active propulsion or motoring system during this fuel cut-off feature and powers the vehicle without noticeably disturbing the operation of the vehicle or sacrificing driveability. The MoGen will propel the vehicle and smoothly transition the vehicle from the idle or stopped state and start the ICE for ICE driving conditions. The transfer of power between the MoGen and ICE or vice versa is transparent to the operator or driver, as the vehicle will perform as if there is only one drive system propelling the vehicle.
During normal operation of the vehicle when the ICE is running, the MoGen will act as an electrical generator to supply electrical power to the vehicle's electrical infrastructure (fans, radios, instrumentation, control, etc.) as well as recharging the battery pack. The battery pack and a power supply, such as a DC—DC converter, will supply power to the vehicle electrical infrastructure the battery pack will power the MoGen when it is operating as the motoring device for the vehicle.
The present invention includes a method and apparatus for controlling the voltage output of a DC—DC converter (Vout) and its relationship to the battery pack and an underhood junction box (UHJB). The UHJB networks the vehicle's electric loads in the vehicle electrical infrastructure. The battery pack will store chemical energy in the form of reactive components that are designed to release the chemical energy as electric power to power the MoGen and the vehicle electrical infrastructure. Typically, a battery pack will comprise a series of individual batteries or battery modules connected in series, parallel, or a combination of both series and parallel, depending on the current and voltage needs of the vehicle.
The battery pack of the present invention is a secondary/rechargeable battery, incorporating the discharge and charge limitations associated with a rechargeable battery such as limited cycle life. The number of times a battery can be recharged and discharged before its fails to meet a selected performance criteria is referred to as the cycle life. A battery is likely to experience differing states of charge (SOC) (the percentage of the full capacity of a battery that is still available for further discharge), in accordance with the power demands of an electric vehicle. These SOCs and the number and depth of the discharges and the recharges will effect the life of the battery. For example, if a lead acid battery is operated in a state where it is only partially charged for an extended period of time, sulfation on the plates of the battery will occur. Sulfation in a lead acid battery involves lead sulfate in the battery developing into large crystals which cannot be readily converted back to an active material, decreasing the charge capacity of the battery and reducing the cycle life of the battery.
The present invention regulates the voltages and the states of charge of battery modules in a battery pack to balance the charging and discharging of the individual battery modules in the battery pack. By regulating the charging and discharging of the individual battery modules in the battery pack, the cycle life of the battery pack will be extended.
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patent: 5905360 (1999-05-01), Ukita
patent: 5932990 (1999-08-01), Kaneko
patent: 5982143 (1999-11-01), Stuart
Aldrich, III William Leonard
Tamai Goro
DeVries Christopher
General Motors Corporation
Tso Edward H.
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