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Vehicle energy storage system control methods and method for determining battery cycle life projection for heavy duty hybrid vehicle applicationsVehicle energy storage system control methods and method for determining battery cycle life projection for heavy duty hybrid vehicle applications description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060232240, Vehicle energy storage system control methods and method for determining battery cycle life projection for heavy duty hybrid vehicle applications. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present disclosure relates generally to vehicle energy storage systems and, more particularly, to vehicle storage system control methods and a method for characterizing traction battery energy and power performance and project remaining service cycle life for heavy-duty hybrid electric vehicle applications. [0002] In electric vehicles and hybrid electric vehicles (e.g., locomotives, off-highway mining vehicles, buses and automobiles), it is necessary to control the operation of the energy storage system in order to obtain high mission performance in terms of average mission speed, range, and/or payload capability, as well as to maximize the operating life of the energy storage system (ESS) and to avoid prematurely degrading thereof. For hybrid vehicles, it is also desirable to maximize the benefits of fuel and/or emissions savings. Existing energy storage systems in such vehicles may include one or more types of batteries, ultra-capacitors and/or flywheel systems. [0003] ESS power command has traditionally been determined based on current drive power requirements, the ESS state of charge (SOC) or stored energy, and static ESS terminal power limits. The power sharing between individual banks in an ESS has further been based on the bank's SOC or stored energy, usable or rated energy capacity, and/or power limits. However, as between one or more individual energy storage banks, there may be a variation in the SOC that, utilizing conventional ESS power commands, could result in premature degradation of the ESS. Thus, it is desirable to be able to obtain greater life/less degradation of the energy storage system. [0004] The performance characteristics for batteries used in electric vehicles and hybrid electric vehicles are normally specified by the manufacturer based on the specific energy (Wh/kg) thereof, volumetric energy density (Wh/l) thereof, and specific power (W/kg) thereof. In particular, the specific power characteristic is based on a "matched impedance" technique, wherein maximum power is transferred from the battery to the load (i.e., half of the power is dissipated in the load, while half of the power is dissipated in the battery's internal resistance). While this approach is useful in comparing one battery to another battery, it is generally not a good indication of the performance in an electric vehicle or hybrid electric vehicle, since the voltage where maximum power is transferred is 50% of the open circuit voltage. [0005] Moreover, the energy rating of the battery is typically the total energy stored in the battery, not the useable energy. In an electric vehicle application, the lower limit for the SOC is typically somewhere around 20% of the total charge, or stated another way, around 80% of the Depth of Discharge (DOD) of the battery. Thus in the electric vehicle application, the useable energy is typically around 80% of the battery's total energy. Accordingly, the battery cycle life for an electric vehicle battery is often reported to be a number of 0-80% DOD cycles, after which point the available battery energy is reduced by 20% from the battery's original energy rating. Accordingly, at the battery's end of life, the electric vehicle will experience a 20% decrease in range. [0006] In contrast, batteries for hybrid vehicle applications are typically operated over a significantly smaller range of DOD's as compared with an electric vehicle. As such, the useable energy of the hybrid vehicle battery is significantly lower than 80% of the battery's energy rating (as is the case for an electric vehicle). However, in the hybrid electric vehicle application, power is of particular concern, and therefore the battery's performance and life cycle should address both the discharge as well as the charge power levels. During vehicle deceleration or while holding speed on a down hill grade, the battery is expected to absorb high power levels. This condition is often referred to as regenerative braking. In small hybrid electric vehicles (e.g., passenger cars and vans), the regenerative braking interval is usually on the order of a few seconds; however, for heavy duty hybrid electric vehicle applications, the regenerative braking periods are on the order of 10 s to 10 s of seconds in duration or longer. As such, an improved method of battery characterization and determining battery life projection is also desirable. BRIEF DESCRIPTION OF THE INVENTION [0007] The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a method for equalizing a storage parameter for a vehicle energy storage system having one or more energy storage banks associated therewith. In an exemplary embodiment, the method includes identifying a quiescent period of operation for the vehicle, and determining whether the value of a defined storage quantity for a first energy storage bank differs from the value of said defined storage quantity for a second energy storage bank by a threshold amount. [0008] During the quiescent period of operation, one of said first and second energy storage banks is discharged and the other of the first and second energy storage banks is charged. The one of the first and second energy storage banks corresponds to the bank having the value of the defined storage quantity exceeding the value of the defined storage quantity of the other of said first and second energy storage banks. [0009] In another aspect, a method for resetting a state of charge (SOC) calculation for a designated energy storage bank of an energy storage system of a vehicle includes, during operation of the vehicle, completely discharging and completely charging the designated energy storage bank. The designated energy storage bank is maintained at a predetermimed high terminal voltage for a specified period of time. Following the specified period of time, a calculated, reset SOC for the designated energy storage bank is defined to be a known SOC capacity. [0010] In another aspect, a method for generating an energy storage control parameter for a vehicle energy storage system includes determining energy storage heat generation information and determining energy storage coolant flow information, and estimating, from the energy storage heat generation information and the energy storage coolant flow information, a storage bank temperature. [0011] In another aspect, a method for generating an energy storage control parameter for a vehicle energy storage system includes receiving energy storage electrical property information, and estimating, from the energy storage electrical property information, a storage bank temperature. [0012] In another aspect, a method for controlling a dynamic discharge rate for one or more energy storage banks in a vehicle energy storage system includes determining a charging/discharging rate of each energy storage bank within the energy storage system. A calculated capacity value for each said energy storage bank is adjusted based upon the determined charging/discharging rate, so as to produce a modified capacity. The modified capacity for each said energy storage bank is used in one or more energy storage system control algorithms. [0013] In another aspect, a method for controlling the operating range of one or more energy storage banks in a vehicle energy storage system includes determining a point at which the energy storage bank has reached a threshold value with respect to an end of life (EOL) condition. Responsive to said threshold value, at least one of an energy storage bank operating parameter and an energy storage bank operating range is reduced. [0014] In another aspect, a method for controlling one or more energy storage banks in a vehicle energy storage system includes determining a remaining life cycle for each of the energy storage banks. A total amount of commanded charging and discharging power commanded is allocated among each of the energy storage banks in accordance with the determined remaining life cycle thereof. [0015] In another aspect, a method for characterizing and projecting remaining cycle life for vehicle storage battery includes performing a series of initial battery characterization tests and performing a series of periodic battery tests during the operating life of the vehicle storage battery. The results of the periodic battery tests are compared with the initial battery characterization tests, and a remaining cycle life is projected for the vehicle storage battery. BRIEF DESCRIPTION OF THE DRAWINGS [0016] Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures: [0017] FIG. 1 is a system-level block diagram of an exemplary energy generation and storage system for hybrid OHVs, suitable for use in accordance with an embodiment of the invention; [0018] FIG. 2 is a flow diagram illustrating an exemplary method for equalizing charge between energy storage banks during quiescent operating periods, in accordance with an embodiment of the invention; [0019] FIG. 3 is a flow diagram illustrating an exemplary method for resetting a state of charge (SOC) calculation for one or more energy storage banks of an energy storage system of a vehicle, in accordance with an embodiment of the invention; [0020] FIG. 4 is a block diagram illustrating a storage bank temperature estimation function implemented by the energy storage system controller, in accordance with a further aspect of the invention; [0021] FIG. 5 is a block diagram illustrating an alternative embodiment of the storage bank temperature estimation function implemented in FIG. 4; Continue reading about Vehicle energy storage system control methods and method for determining battery cycle life projection for heavy duty hybrid vehicle applications... 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