1. Field of the Invention
The present invention relates to the field of batteries, particularly lead-acid batteries. Even more particularly, the invention relates to batteries having embedded computer systems and methods that measure internal operating characteristics of multi-cell batteries and make information available externally, for example to an external charging system or to warn that the battery is approaching the end of its life. The invention also particularly relates to performing active and/or passive cell balancing within the battery, optionally in conjunction with an external intelligent charging system.
2. Description of the Background Art
All batteries fail. Battery failure is the number one complaint of new car owners. Batteries typically fail unexpectedly without warning, which is undesirable.
Automobile manufactures typically provide only the real-time state of the car's charging system (alternator) when the engine is running The battery is only one component of this system. This system warns the motorist when there is a problem with the charging system by using a dash mounted voltmeter, ammeter or more commonly a warning lamp which is often referred to as the “idiot light”. This information should not be confused nor equated with the operating state or the overall health of the battery, itself.
The typical automobile lead-acid starter battery consists of six electrochemical cells embedded in a polymer case. Because the cells are encased, cell voltage measurements cannot be taken, the temperature or pressure inside the battery is not known, and for those batteries without filler caps the level of the electrolyte cannot be determined. Generally, the internal operating characteristics of the individual cells of the battery, and the battery itself, are unknown.
The single most prevalent cause of lead-acid battery failure is incorrect battery charging. Overcharging causes grid corrosion. Undercharging causes battery sulfation. Both lead to premature battery failure. Unfortunately, charging systems in today's automobiles are blind devices, in that they do not know the internal operating characteristics (e.g., voltage, pressure, temperature, specific gravity, electrolyte level, etc.) of the battery, much less the operating characteristics of the individual cells of the battery. None of today's vehicular batteries provide the information required by charging systems to perform optimal charging.
Moreover, when the voltages of individual cells inside a lead-acid battery differ by as little as one one-hundredth of a volt, the health of the battery is in jeopardy. An imbalance causes weaker cells to become progressively undercharged and the stronger cells to suffer the consequences of being consistently overcharged. Unless this imbalance can be quickly ameliorated the battery will prematurely fail.
Cell balance is typically restored in lead-acid batteries by passive equalization whereby temporarily overcharging the battery at a voltage of 14.4 volts for 15 minutes is used in an attempt to bring weak cells into alignment. This approach is a risky proposition. The external charging system does not know the voltage of each individual cell, so it does not know if or when to apply a cell balancing routine nor will it know if the cell balancing attempt was successful. The external charging system also does not know the level of the electrolyte of each cell or the internal temperature and pressure of the battery. If the strong cells are excessively overcharged, their positive plates will disintegrate or buckle and the excessive temperature generated in the cell by overcharging will cause loss of electrolyte. On the other hand, if the weak cells are not sufficiently charged, the cell imbalance will remain and the battery will die prematurely.
The present invention overcomes the problems associated with the prior art by providing a battery with an embedded computer system. The computer system is capable of, among other things, measuring operating parameters of the battery (individual cell voltages, the electrolyte level of each cell, internal temperature, internal pressure, etc.) and providing this sensor information externally if desired via an external interface. The computer system also is capable of measuring time and includes memory for storing a data history, as well as various battery management algorithms. The algorithms can render an optimal charging voltage or charging current for the battery based upon its internal sensor data, and communicate the optimal charging information to an external smart charging system. The algorithms can use the sensor data and sensor history to detect alarm conditions that indicate the imminent failure of the battery. The computer system may also include facilities for shunting current around individual cells or for transferring energy from strong cells to weak cells using, for example, magnetic components or capacitors.
The present invention also provides the ability to first detect a cell imbalance inside the lead-acid battery and then to carefully control the process by which the imbalance is ameliorated. The present invention makes use of a computer system that can detect such an imbalance. Once detected, a closed loop control path is established with an external intelligent charging system. Different charge requests are made of the intelligent charger. All the while the battery's internal state is carefully monitored to avoid permanent damage.
This invention can also be properly viewed as a research tool. There is a multitude of things that can cause a cell imbalance. Some examples are partial shorts between positive and negative plates, partial shorts between plates and straps, improper electrolytic levels, crystallized lead sulfate accumulations and incorrect specific gravity. This invention is heuristic in nature in that there is no established methodology that correlates or matches charging schemes to the underlying cause of a cell imbalance. A charging regime is tried by a cell balancing algorithm and its results are monitored. If the cell imbalance persists a different cell balancing algorithm is tried. This next charging regime may be similar to the previous attempt or may be radically different depending upon any detectable improvements. If no improvement occurred, the next charging regime will depart from the previous. The internal state of the battery continues to be monitored to insure no harm is being done. When a successful result is determined the successful technique is saved in a history file. This history is made readily available over the communication path normally established between battery and battery charging system. If the underlying cause of the imbalance is not apparent, such as plate sulfation, a post mortem can be performed on the battery in order to more properly correlate successful cell balancing techniques to the root cause of the imbalance. With this information battery manufacturers will have better insight into the failure mechanisms of their batteries while automobile and battery charger manufacturers will be able to build better charging systems.
Depending upon the facilities and the makeup of the embedded computer system and its ability to control the external charging system, either passive, active or a combination of the two equalization schemes can be used to fix cell imbalances inside a multi-cell enclosed battery such as a lead-acid starter battery.
For passive equalization schemes, the embedded computer system establishes a closed-loop control path with an external intelligent charging system. Different charge requests are made of the intelligent charger. All the while the battery's internal state is carefully monitored to avoid damage. A cell balancing algorithm can be made to mimic the typical 14.4 volt flat charge rate of 15 minutes that is performed by many of today's open-loop battery chargers. A different cell balancing algorithm can be made to issue a much higher voltage request for a much shorter period of time. Still other algorithms can issue cyclic voltage requests that create pulse charging. At the termination of each algorithm a check is made to see if the cells have been brought back into balance. If not, a different algorithm may be attempted.
For active equalization schemes the embedded computer system, depending upon the embedded computer systems hardware facilities, can perform power switching or dissipative load switching. Dissipative load switching involves temporarily activating resistive loads across individual cells in order to shunt current away from saturated cells. Power switching involves the transfer of energy from strong cells to weak cells using magnetic components or capacitors.
According to yet another embodiment of the invention, the remaining life of a battery can be determined, and a warning can be generated when the battery is nearing the end of its life. According to the invention, a computer system embedded inside the battery includes facilities for measuring time and temperature, includes storage facilities for retaining a history of these measurements, knowledge of the age of the battery, and optionally, empirical data about the effect of temperature on battery lifespan. In addition, the computer system includes algorithms for predicting the remaining life of the battery based upon time and temperature measurements, the current age of the battery, and optionally the empirical data. Finally the computer system includes means to communicate to the outside world, for example, the operator of a vehicle, by using a low power wireless technology such as Bluetooth Low Energy which is a feature of Bluetooth 4.0.
The present invention is described with reference to the following drawings, wherein like reference numbers denote substantially similar elements:
The following descriptions are provided to enable any person skilled in the art to make and use the invention and are provided in the context of the particular embodiments. Various modifications to these embodiments are possible and the generic principles defined herein may be applied to these and other embodiments without departing from the spirit and scope of the invention. The embodiments described herein perform their intended functions using a computer system embedded inside a lead-acid battery. Special notification is made with regard to battery technology. While the present invention is particularly well-suited to lead-acid batteries, the generic principles described herein apply to any battery type. Thus the invention is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles, features and teachings disclosed herein.
In accordance with one embodiment, the present invention makes use of a computer system that resides inside a flooded lead-acid battery. The computer system includes a means to measure individual cell voltages, the level of the electrolyte in each cell and the internal temperature of the battery. The computer system includes a means to communicate with an external battery charging system through the power cable attached to the battery. The computer system's central processing unit includes a means to measure time and includes facilities for storing data. The computer system's non-volatile memory includes algorithms that have a means to detect cell imbalances and to perform cell balancing by sending charge request messages to an external charging system.
In accordance with another embodiment, the present invention makes use of a computer system that resides inside a sealed lead-acid battery. The computer system includes a means to measure individual cell voltages, the internal pressure of the battery and the internal temperature of the battery. The computer system includes a means to communicate with an external battery charging system through the power cable attached to the battery. The computer system's central processing unit includes a means to measure time and includes facilities for storing data. The computer system's non-volatile memory includes algorithms that have a means to detect cell imbalances and to perform cell balancing by sending charge request messages to an external charging system.
In accordance with yet another embodiment, the present invention makes use of a computer system that resides inside a sealed lead-acid battery. The computer system includes a means to measure individual cell voltages and internal battery current and includes the means to perform active cell equalization using dissipative load switching. The computer system may optionally include a means to communicate with an external battery charging system through the power cable attached to the battery but this means is not essential in the performance of active equalization and is not included in this embodiment. The computer system's central processing unit includes a means to measure time and includes facilities for storing data. The computer system's non-volatile memory includes algorithms that have a means to detect cell imbalances and to perform active cell equalization by communicating with the active cell equalizer subsystem.
Active equalization includes dissipative load switching and power switching. Dissipative load switching involves temporarily switching resistive loads across saturated cells. Power switching involves the transfer of energy from strong cells to weak cells using magnetic components or capacitors. Until now, neither of these techniques could be used for lead-acid batteries because the individual cell voltages were unknowable and the means to actively equalize cells encased in a battery did not exist.
This invention changes the age old paradigm whereby the battery charging system blindly controls the procedure by which the cells in a multi-cell battery, such as the ubiquitous twelve volt lead-acid battery, can be kept in balance. With this invention the battery is now in control.
For passive equalization, a closed loop system is established with the charging device. The battery knows when a cell is out of balance. The battery possesses the heuristic means to reduce or remove a cell imbalance by controlling charge applications while monitoring internal sensors to insure that no harm is done. In other words, the battery possesses the means to learn from trial and error which charge strategy works best to reduce or remove cell imbalances.
For active equalization, the battery has the means to individually control the amount of energy applied to individual cells. Highly charged cells receive less energy, weak cells get more. Because this invention is a computer program that executes on a computer system embedded inside a multi-cell battery it has access to the voltage of each individual cell and therefore can detect a cell imbalance. Furthermore, because the embedded computer system includes a means to communicate with an external charging system, the invention has a means to control the amount and duration of charge applied to the battery when a cell balancing operation is in progress. Moreover, because the embedded computer system has access to the internal temperature of the battery, the internal pressure of the battery, the electrolytic levels, and other sensor information, this invention can ensure that the battery is not damaged by the aggressive charging schemes used by cell balancing procedures.
This invention can also be properly viewed as a research tool. There is a multitude of things that can cause a cell imbalance. Some examples are partial shorts between positive and negative plates, partial shorts between plates and straps, improper electrolytic levels, crystallized lead sulfate accumulations and incorrect specific gravity. This invention is heuristic in nature in that there is no established methodology that correlates or matches charging schemes to the underlying cause of a cell imbalance. A charging regime can be tried by a cell balancing algorithm and its results evaluated. If the cell imbalance persists a different cell balancing algorithm may be attempted. This next charging regime may be similar to the previous attempt or may be radically different depending upon detectable improvements. If no improvement occurred, the next charging regime will depart from the previous. The internal state of the battery continues to be monitored to insure no harm is being done. When a successful result is determined the successful technique is saved in a history file. In like manner the algorithms that control power and dissipative load switching can be heuristically modified, tested and evaluated in order to find and save the most effective techniques. This history is made readily available over the communication path normally established between battery and battery charging system. New and improved algorithms can also be downloaded to the embedded processor, tested and evaluated. When the battery eventually fails, as all batteries do, a post mortem can be performed on the battery in order to determine the root cause of the failure. With this type of information battery manufacturers will have better insight into the failure mechanisms of their batteries while automobile and battery charger manufacturers will be able to build improved charging systems.
Computer system 400 includes an electrical connection to battery terminal 404 through conductor 406. Transceiver 408 is used to receive and transmit data between central processor 410 and one or more external devices (not shown) attached to the terminal 404 power cable using the industry standard Local Interconnect Network (LIN) vehicle bus protocol. Temperature sensor 412 measures the temperature of the electrolyte. Timer 414 measures the elapsed time between temperature samples. Central processor 410 also stores the age of the battery 402 in a non-volatile memory 416. For example, the manufacturing date of battery 402 can be stored in memory 416, which can be used to determine the age of the battery 402, for example, based on the difference between the manufacturing date and a current date maintained by central processor unit 410.
The lead-acid battery's lifespan is reduced by half for every 15° F. above its optimal operating temperature of 77° F. The embedded computer system 400 makes use of this knowledge to notify the driver, based upon the length of time in service and operational temperature measurements, that the battery 402 is approaching its predicted end of life. The following equation is used for calculating the shortened life of the battery when the temperature is above 77° F.:
Life Expectancy=50 months·(½)(x-77F)/15F,
where “x” is the temperature in Fahrenheit.
According to the embodiment shown in
The lead-acid battery's lifespan is greatly affected by its operating temperature. Empirical data shows that, when compared to a battery operating at 25° C., the life of the battery is approximately 200% longer at −10° C., 180% longer at 0° C., 160% longer at 10° C., 140% longer at 15° C., 120% longer at 20° C., 15% shorter at 30° C., 25% shorter at 35° C., 50% shorter at 40° C. and 75% shorter at 50° C. Thus, empirical data reveals that the lifespan of lead-acid batteries is adversely affected by an increase in temperature. A battery operated at 32° F. (0° C.) will last 3 times longer than a battery operated at 100° F. (37.8° C.).
Empirical data also shows that, as of 2010, the current average life of the lead-acid starter battery in multiple northern locations in the United States is 59 months and in multiple southern locations in the United States is 47 months. Note that this empirical data is based on a post mortem analysis of 1496 batteries sampled between September and December of 2009 from ten locations across the nation. Because the average temperature in southern locations of the U.S. more closely approximates the 25° C. norm, the 47 month lifespan is used as the baseline for predicting the life of the battery in these particular embodiments.
It is the intent of this invention to make use of this empirical data in a battery monitoring system embedded in the battery. The invention will notify the driver, based upon the length of time in service and operational temperature measurements, that the battery is approaching its predicted end of life.
Computer system 600 includes a power terminal 604 and a transceiver 606. Transceiver 606 uses an antenna 608 to receive and transmit data between a central processor 610 and one or more external consoles 607 (e.g., an in-dash display near the vehicle operator, a smartphone, etc.). In one embodiment, transceiver 606 communicates using a low power wireless technology such as Bluetooth Low Energy, which is a feature of Bluetooth 4.0. Temperature sensor 612 measures the temperature inside the battery 602. Timer 614 measures the elapsed time between temperature samples. Non-volatile memory 616 stores the date of manufacture of the battery 602 and empirical data for the battery and provides this information to central processor 610 as needed.
Central processing unit 610 samples temperature sensor 612 on a periodic basis determined by timer 614 and saves this temperature sample in non-volatile data store 616. On a less frequent periodic basis central processing unit 610 calculates an average temperature on the previously saved temperature samples and saves this calculation in data store 616. On a still less frequent periodic basis central processing unit 610 averages all of the saved average temperature calculations and uses this overall average temperature to calculate the remaining life of the battery. When the remaining life of the battery approximates zero days (or falls below some other predetermined threshold), central processing unit 610 makes use of transceiver 606 to send a warning message via antenna 608 to an external device (e.g., the console display 607 near the vehicle operator).
Computer system 800 advantageously extends the life of the battery 802, warns an operator using the battery 802 that the battery 802 is near the end of its life, and/or facilitates transmitting operational and charging characteristics of the battery 802, including its individual cells, outside of the battery 802 such as to a smart battery charging system 826. For example, computer system 800 can measure the operational characteristics of the battery 802 and its individual cells using any of its sensors and communicate this information external to the case of battery 802 via transceiver 808 and antenna 810 as described in U.S. patent application Ser. No. 12/321,310, which is incorporated by reference herein in its entirety.
Computer system 800 is also adapted to store battery-specific information (e.g., battery construction type, temperature dependent, optimal charge rate tables, manufacturing date and serial number, etc.) in its memory 806. Computer system 800 can retrieve this information and communicate it (along with any sensor information) external to the battery 802, for example to external smart charging system 826, as described in U.S. patent application Ser. No. 12/380,236, which is incorporated by reference herein in its entirety. The information provided to the smart charging system can be used by the smart charging system to determine the appropriate charging parameters for the battery 802.
Similarly, computer system 800 can also include the battery-specific information described above and algorithms for internally calculating a desired charge rate using the algorithms and battery-specific information stored in the memory 806, as well as sensor data provided by its sensors 812, 814, 816, 818, etc. The computer system 800 can then establish a connection with and request a desired charge rate from the external smart charging system 826 via the transceiver 808 and antenna 810. The computer system 800 can also generate charging (e.g., over-charging, temperature, etc.) warnings and communicate those warnings externally to the battery 802, such as to the smart charging system 826 and/or to an operator console 828. For example, if the level of the electrolyte does not completely cover all plates, no charging should be performed and the operator of the vehicle should be warned. As another example, if the specific gravity has dropped sufficiently, a carefully-monitored higher-than-normal equalization charge should be applied to the battery. As still another example, if the temperature of the battery spikes or the internal pressure of the battery becomes excessive, all charging should stop in order to prevent thermal runaway or excessive loss of electrolyte. Indeed, computer system 800 can employ any of the embodiments and methods described in U.S. patent application Ser. No. 12/454,454, which is incorporated by reference herein in its entirety. Computer system 800 is also adapted to detect the voltage between the battery terminals 822 and 824 via a voltage sensor 830. Additionally, memory 806 includes algorithms that the central processor 804 can execute to determine if the battery 802 is behaving erratically and near the end of its life. For example, the algorithms can use the data from voltage sensor 830 and other information, such as temperature data from temperature sensor 814 and time information from timer 814, to determine if the erratic behavior is occurring. In the case of an engine starter battery, the computer system 800 can determine if the state of charge of the battery 802 is low, if the battery 802 is producing erratic engine start times as compared to a temperature-indexed start time history, and/or if the battery 802 has an erratic initial start voltage (indicative of a starter motor engaging) as compared to a temperature-indexed initial start voltage history. If the battery 802 has a low state of charge and/or is behaving erratically as compared to historical readings, the computer system 800 can provide a warning outside the battery, via transceiver 808 and antenna 810, that the battery 802 is nearing the end of its life and needs replacement. Detailed algorithms for determining the health of the battery 802 are provided in U.S. patent application Ser. Nos. 13/272,905; 12/075,212;12/319,544; and 12/070,793 which are incorporated by reference herein in their entireties.
Finally, computer system 800 can selectively employ any or all of the embodiments described previously herein with respect to the preceding figures. For example, computer system 800 can employ passive and/or active cell balancing to extend the life of battery 802. Computer system 800 can also keep track of the remaining life of the battery 802 (e.g., based on empirical battery information, etc.) and warn of when battery 802 is nearing the end of its life by communicating with operator console 826. See, for example, U.S. patent application Ser. No. 12/655,275 and U.S. Provisional Patent Application Ser. Nos. 61/545,847 and 61/592,967, all of which are incorporated by reference herein in their entireties.
The description of particular embodiments of the present invention is now complete. Many of the described features may be substituted, altered or omitted without departing from the scope of the invention. Deviations from the particular embodiments shown will be apparent to those skilled in the art, particularly in view of the foregoing disclosure.
This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 12/655,275, filed on Dec. 28, 2009 and having at least one common inventor, which is incorporated by reference herein in its entirety. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 12/321,310, filed on Jan. 15, 2009 and having at least one common inventor, which is incorporated by reference herein in its entirety. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 12/380,236, filed on Feb. 25, 2009 and having at least one common inventor, which is incorporated by reference herein in its entirety. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 12/454,454, filed on May 18, 2009 and having at least one common inventor, which is incorporated by reference herein in its entirety. This application is also a continuation-in-part of co-pending U.S. patent application Ser. No. 13/272,905, filed Oct. 13, 2011 by at least one common inventor, which is a continuation-in-part of each of U.S. patent application Ser. No. 12/075,212, filed Mar. 10, 2008 by at least one common inventor, U.S. patent application Ser. No. 12/319,544, filed Jan. 8, 2009 by at least one common inventor, and U.S. patent application Ser. No. 12/070,793, filed Feb. 20, 2008 by at least one common inventor, each of which is incorporated by reference herein in its entirety. This application also claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/545,847, filed on Oct. 11, 2011 and having at least one common inventor, which is incorporated by reference herein in its entirety. This application also claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/592,967, filed on Jan. 31, 2012 and having at least one common inventor, which is incorporated by reference herein in its entirety.
Number | Date | Country | |
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61545847 | Oct 2011 | US | |
61592967 | Jan 2012 | US |
Number | Date | Country | |
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Parent | 12655275 | Dec 2009 | US |
Child | 13649881 | US | |
Parent | 12321310 | Jan 2009 | US |
Child | 12655275 | US | |
Parent | 12380236 | Feb 2009 | US |
Child | 12321310 | US | |
Parent | 12454454 | May 2009 | US |
Child | 12380236 | US | |
Parent | 13272905 | Oct 2011 | US |
Child | 12454454 | US | |
Parent | 12075212 | Mar 2008 | US |
Child | 13272905 | US | |
Parent | 12319544 | Jan 2009 | US |
Child | 12075212 | US | |
Parent | 12070793 | Feb 2008 | US |
Child | 12319544 | US |