Patent Publication Number: US-2012037438-A1

Title: Hybrid Electric Vehicle Battery Protection System Through Capacitor Bank Energy Buffer

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a hybrid vehicle system that utilizes a combined battery and capacitor electrical energy storage system that reduces related wear and tear on the batteries when exposed to a start up energy surge that has the effect of “shock loading” the anode and cathode poles of the battery bank. 
     2. Discussion of the Related Art 
     Internal Combustion/Electric Hybrid vehicles are becoming more and more important as a means of maximizing fuel economy by fully utilizing and optimizing the energy systems of the vehicle, be it reducing the hydrocarbon fuel required for acceleration through supplemental battery stored energy, or capturing the braking energy through regenerative braking technologies. 
     Technologies have evolved so that an Internal Combustion Engine coupled to an electric motor/generator can work seamlessly with a battery bank to power the vehicle. 
     The battery bank is an array of lower voltage modules (possibly 6-12 Volts) connected in a series string to achieve the desired voltage, by example 230-400 volts, with the strings then connected in parallel to achieve the desired power requirements wherein current flows could be, for sake of this discussion, on the order of 6-10 Amp hours at the said voltage, more or less as per the designs of the manufacturer of the vehicle. 
     In hybrid truck and bus systems, typically the Internal Combustion Engine is sized significantly to match the power requirements of constant momentum, while the increased energy needs of acceleration, particularly as in moving forward from a dead stop, are provided by, or at least substantially assisted by, the battery bank. 
     At the instant that acceleration is initiated the battery bank experiences a dramatic outrush of energy as the electric motor windings offer no resistance to current flow till the magnetic flux fields are established in the motor. In these few hundredths of a second the electron outflow from the battery bank can be between 50-200% of normal steady state current flow. On a micro level within, by example a Lithium-Ion Battery, such a discharge surge causes Li + -ion particles to “explode” off of the Carbon Anode plates or film. 
     The introduction of a capacitor bank in parallel to the battery bank serves as an energy reservoir to cover the above instantaneous electrical surge, thereby reducing the demands on the battery system and thus extending the life of the batteries. Unlike a battery, rapid current flow off of and onto the metal plates of the capacitor does not impact the durability of the capacitor for upwards of a million cycles. 
     Once energy flows from the capacitor bank it will be replenished in the same manner as the battery bank when the hybrid system switches into recharging mode and current flows reverse. 
     If the customer so desires the capacitor bank could include electrical and/or electronic circuitry to activate indicator lights on the housing of the capacitor bank or enable the capacitor bank to be connected to the vehicles electronic and/or computer control systems. 
     As the customer desires the capacitor bank can be enclosed in a container, the sealing of which, the atmospheric conditioning of which and the electrical isolation of which, will be dictated by code requirements and customer necessities. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, a hybrid vehicle system is disclosed that employs an ultra or super capacitor bank coupled in parallel with the battery bank of the hybrid system through a bus bar/line. In one embodiment the power and energy rating of the capacitor bank will be the same as the battery bank, and both are rated as capable of sustaining the same current flow. As the loading of the system changes the voltage swing of the bus bar/line, battery bank and capacitor bank will be the same owing to the parallel circuit configuration. The battery bank&#39;s energy demand in the first few hundredths of a second of acceleration is buffered by the capacitor bank, thus extending the life span of the batteries. During regular maintenance the capacitor bank and battery bank can be isolated from one another by means of a switch in series with the capacitor bank. 
     Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
     The remaining pages draw understandings from the above base patent and will be developed in conjunction with the discussion of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a schematic block diagram of a hybrid vehicle, where the system includes a battery bank and a super capacitor bank connected in parallel wherein the energy demands placed on the battery bank are buffered by the capacitor bank, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following discussion of the embodiments of the invention directed to a hybrid vehicle system that employs a ultra/super capacitor and a battery is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, the battery bank and capacitor bank combination described herein has particular application for a hybrid vehicle. However, the battery bank and capacitor bank combination system may have other applications beyond vehicle applications. 
       FIG. 1  is a schematic block diagram  100  of a hybrid vehicle internal combustion (IC) engine and electric system  10 , complete with engine controls  14 , provided by others, additionally including a battery bank  20  having an array of battery modules connected in series and parallel  22 , also by others, electrically coupled in parallel with a capacitor bank  30 . The battery bank and capacitor bank connected in parallel via a positive bus bar/line  40  and a negative bus bar/line  50  provides electrical power to the electric motor component  12  of the hybrid vehicle. On acceleration electrical energy will flow jointly from the battery bank  20  and capacitor bank  30  to the electric motor  12  with the initial first fractional amount of energy being provided by the capacitor bank  30  owing to the far lower amount of electrical resistance of the capacitor bank  30  compared to the battery bank  20 . A switch  60 , possibly manually operated, is connected in series between the positive bus bar/line  40  and the capacitor bank  30  that selectively disengages the capacitor bank  30  from the positive bus bar/line  40  for times of maintenance or if a safety shut down is required. As the battery bank  20  and the hybrid vehicle system are by others it would be their election to include a similar isolating switch for the battery bank  20 . 
     According to the invention, the hybrid internal combustion/electric motor drive system  10  includes a battery bank  20  and a capacitor bank  30  electrically coupled in parallel to the positive bus bar/line  40  and the negative bus bar/line  50 . As per detailed discussions below, the battery bank  20  and the capacitor bank  30  are discharged and charged simultaneously through the bus bar/lines during the operation of the system thereby reducing the initial shock to the battery bank  20  in first few hundredths of a second as most of the energy would flow from the capacitor bank  30  as previously stated. This difference in current flow is shown in the distinctions between  FIG. 2  and  FIG. 3 .  FIG. 2  shows the typical current outflow from the battery versus time, noting the dramatic discharge in the first fraction of a second.  FIG. 3  highlights the effect of the capacitor bank ameliorating the impact of that initial current surge. In times of electrical recharging of the battery bank  20 , such as in regenerative braking or idling, the capacitor bank would likewise be simultaneously be recharged. 
     The battery bank  20  is matched to the operating voltage of the hybrid vehicle system, by others, by means of a proper selection and connection of battery modules  22  in series to achieve the desired voltage and in parallel to achieve the desired Amp-hour rating. The battery bank  20  can be any rechargeable battery system, such as Lithium ion (Li-ion) batteries, a Nickel-metal-hydride (NiMH) batteries, Lead-acid batteries, or suitable others. The voltage specification of the Capacitor bank  30  is likewise matched to the operating voltage of the hybrid vehicle system, as per this invention, by selecting super capacitors which are either individually rated greater than the vehicles operating voltage or several capacitors in a series string, as in the battery example just noted, to achieve the desired voltage. Again, as in with the battery bank  20  above, individual or capacitor strings can be connected in parallel to enable the desired Amp-hour ratings so as to provide the desired amount of energy storage to sustain the system for the above specified fraction of a second. 
     A switch  60  selectively disengages capacitor bank  30  from the positive bus/bar line  40  to disconnect the capacitor bank  30  from the battery bank  20  when shut down/maintenance is required. 
     If others so elect, the battery bank  20  could include various sensors and the like for monitoring the temperature of the batteries  24 , as well as their respective states of charge sensor monitoring system  70  that could be provided by others or the holder of the patent. Additionally, similar sensors could be attached to the capacitors  34  of the capacitor bank  30 . A controller  14  exists within the hybrid motor, generator and battery system, as designed and provided by others, primarily to manage the state of charge of, and energy flow to, the battery bank  20 . Given the fractional amount of energy in the capacitor bank  30  it can float in parallel with the battery bank  20  without needing additional controls. The said controller will also control other systems and switches consistent with the hybrid technologies discussed herein that are outside the prevue of this patent but are “well known in the trade”. 
     The hybrid internal combustion/electric motor drive system  10  includes a DC traction motor  12  as per the design and patents of others. The traction motor  12  provides the traction power to operate the vehicle, as is well understood in the art. The traction motor  12  can be any suitable motor for the purposes described herein. During regenerative braking when the traction motor  12  is operating as a generator, electrical DC power from the motor  12  is applied to the bus lines  40  and  50  to recharge the battery bank  10  and the capacitor bank  20 . 
     Additionally, the battery bank  10  can be used for start-up and shutdown of the system  10 , even when the capacitor bank  20  is empty. 
     The foregoing discussion describes and discloses and examples embodying the present configurations of the present invention. Those skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.