Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
1999-12-23
2001-03-06
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
Reexamination Certificate
active
06198253
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of rechargeable batteries, and more particularly to an intelligent battery that internally monitors its own operating condition, its own need for maintenance, and its own useful life, and communicates this information to a user or to an intelligent device.
BACKGROUND OF THE INVENTION
With the proliferation of portable electronic devices, the use of rechargeable batteries has become increasingly important. Rechargeable batteries can now be found in devices as simple as a flashlight, as important as notebook computers, and as vital as portable medical equipment. An example of a portable medical device which is dependent on a rechargeable battery pack is a portable defibrillator unit.
Portable defibrillator units are used by emergency medical technicians on persons suffering from certain types of abnormal heart rhythms, e.g., ventricular fibrillation, to shock the heart back into a normal beating pattern. Although many of these portable defibrillators have the ability to operate off of AC line current, when used in the field, portable defibrillators are almost totally dependent on rechargeable battery packs. The portable battery packs provide the power both to operate the internal electronics of the defibrillator and to provide the charge source for the therapeutic shock. In order to provide the power source for charging the shock delivery circuitry of the defibrillator, it is necessary that the portable battery pack be capable of providing a relatively large current draw over a relatively short period of time. If the battery is unable to supply this current when demanded, the delivery of the therapeutic shock may be delayed or prohibited.
Seconds count in the application of the therapeutic shock to a person suffering a heart attack. Swapping a bad battery pack in and out of a defibrillator may waste this precious time, as may waiting for a marginally functional battery to deliver the charge necessary for the therapeutic shock. It is important, therefore, for the user of a portable defibrillator to make sure that a reliable, working battery pack is available. This has usually meant having an ample supply of extra battery packs on hand. Unfortunately, one can usually only guess the battery pack's ability to reliably deliver high current charging pulses. While users normally log the age and use of the battery manually to predict its current condition, the accuracy of the predictions are both dependent on the accuracy of the records and the validity of the underlying assumptions of the predictions.
In response to the demand for reliable batteries, computer and battery manufacturers have recently been developing “smart batteries” which internally measure battery variables such as voltage and current flow in and out of the battery and then apply predictive algorithms to estimate the battery's state of charge. The battery's predicted state of charge can then be communicated to a portable electronic device such as a notebook computer (i.e., a “host”) over a communication bus. This is useful in applications where a computer needs to find out if there is enough charge in the battery to save a word-processing file to a disk drive. However, the prediction of a smart battery's state of charge must be much more reliable in medical device equipment, such as a defibrillator, where the state of charge is crucial to the appropriate medical treatment of an individual. This is particularly true if the only way to determine if the battery is able to deliver the charge is by first inserting it into the host unit.
The basic method for keeping track of the state of charge (“SOC”) of a smart battery is to create a coulomb counter that adds the electrons going in and subtracts the electrons going out from a running counter. However, energy that goes into the battery does not all end up as stored charge—some of it is expended as heat in the charging process. For this reason an ‘Efficiency Coefficient’ (EC) is used to maintain the accounting. An EC can be estimated based on testing a statistically significant sample of batteries and choosing a value that represents the worst case battery. One method devised by the industry to avoid the error in calculating SOC is to establish a value for a fully charged battery and then cease accounting for the charge once the calculated charge has reached this value, regardless of measured input current.
The ability of a battery to deliver its charge on demand depends both on battery charge and proper battery maintenance. Rechargeable battery packs are currently manufactured using a number of known battery chemistries, including nickel cadmium (NiCd), sealed lead acid (SLA), nickel-metal hydride (NiMH), lithium ion (Li-ion), lithium polymer (Li-polymer), and rechargeable alkaline. The most popular choice for rechargeable batteries is currently the NiCd chemistry because it is relatively inexpensive, is fast and easy to charge, has excellent load performance even at cold temperatures, and is capable of withstanding a high number of charge/discharge cycles. Over the course of the life of the NiCd battery, however, the cycling of the battery causes it to develop crystalline formations that substantially decreases the battery's ability to hold charge. This is commonly referred to as “memory”. It is known that “conditioning” the battery, which involves fully discharging the battery and then charging the battery back to the state of full charge, can substantially reduce NiCd memory. This process helps breakdown the crystalline structure developed over time and enables the battery to receive and store a greater charge.
If the NiCd “memory” goes undetected, the battery may show a voltage that indicates a full charge while it actually does not hold sufficient charge to supply the high current pulse required by a demanding application such as a portable defibrillator. While this “memory” problem has long been recognized, the conditioning required to correct it has depended on the user manually conditioning the battery on a regular basis. This meant that the user had to estimate when the battery required conditioning and then manually put the battery through a conditioning process. The actual discharging and charging of the battery during conditioning can take hours during which the battery is out of service. Due to these limitations, rechargeable battery packs are sometimes used past the period in which they should be conditioned, used until they fail, or are simply discarded much earlier than they would actually need to be if they were properly maintained.
Accordingly, a method and apparatus for a rechargeable battery pack that informs the user that the battery pack is ready to use, requires maintenance, or should be discarded, is needed. Further, the method and apparatus should be able to communicate with an intelligent battery maintenance and testing system that can charge, condition, and test the battery in accordance with the information that the battery maintains. As explained in the following, the present invention provides a method and apparatus that meets these criteria and solves other problems in the prior art.
SUMMARY OF THE INVENTION
In accordance with the present invention, an intelligent battery is provided which is capable of self-monitoring its state of charge, its need for maintenance, and the end of its useful life. The battery includes a user interface and display through which information regarding the state of charge, maintenance requirements and end of useful life can be displayed to a user or requested by a user by pushing a depressible keypad. In addition, the battery includes a monitoring circuit for self-monitoring that includes a communication interface for communicating this information to another device.
In one embodiment of the present invention, the monitoring circuit of the intelligent battery comprises an internal circuit board connected by a plurality of conductive rods to a plurality of external communication interface pads and a plurality of ext
Choi Peter Y.
Firman Stephen L.
Gustavson Douglas M.
Johnson Stephen B.
Kurle Wayne D.
Christensen O'Connor Johnson & Kindness PLLC
Medtronic Physio-Control Manufacturing Corp.
Tso Edward H.
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