Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-05-10
2001-07-03
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C320S162000, C324S433000
Reexamination Certificate
active
06255801
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to batteries and, more specifically, to a system and method for assessing the capacity of a battery and a power plant employing the system or the method.
BACKGROUND OF THE INVENTION
The traditional reliability of telecommunication systems that users have come to expect and rely upon is based, in part, on the reliance on redundant equipment and power supplies. Telecommunication switching systems, for example, route tens of thousands of calls per second. The failure of such systems, due to either equipment breakdown or loss of power, is unacceptable since it may result in a loss of millions of telephone calls and a corresponding loss of revenue.
Power plants employable in standby applications (e.g., telecommunications, UPS applications) address the power loss problem by providing the system with an energy reserve (e.g., a battery) in the event of the loss of primary power to the system. Power plants employable in other applications (e.g., cyclic, photovoltaic or automotive applications) may likewise require an energy reserve in the event the primary power is insufficient (or unavailable) to power the entire system. For example, in cyclic applications, the energy reserve may be employed to supplement the primary power during periods of peak usage.
A power plant that powers telecommunications systems commonly includes a number of batteries, rectifiers and other power distribution equipment. The primary power is produced by the rectifiers, which convert an AC main voltage into a DC voltage to power the load equipment and to charge the batteries. The primary power may, however, become unavailable due to an AC power outage or the failure of one or more of the rectifiers. In either case, the batteries then provide power to the load. Redundant rectifiers and batteries may be added to the power plant as needed to increase the availability thereof.
The power plant commonly employs lead-acid batteries (e.g., valve-regulated lead-acid (VRLA) batteries) as the energy reserve. The batteries are typically coupled directly to the output of the rectifiers and may instantly provide power to the load in the event an AC power outage occurs. During normal operation, the batteries are usually maintained in a fully charged state to maximize a duration for which the batteries can provide energy to the load equipment.
As a battery ages, however, its capacity or energy-storage capability decreases thereby reducing a duration for which the battery can provide energy, even when fully charged. In many applications, particularly telecommunications applications, the battery is considered to have failed when its actual capacity has fallen below a threshold, such as 80% of its rated capacity (for some telecommunications applications). A failed battery should be replaced in an orderly fashion to maintain the availability of the power plant. It is crucial, therefore, to be able to assess whether the capacity of a particular battery has fallen below its threshold.
An accurate method for assessing the capacity of the battery is to fully discharge the battery. Completely discharging the battery to assess the capacity, however, may present major disadvantages. If an AC power outage occurs during or after the discharge test, but before the battery has been fully recharged, the full energy reserve provided by the battery will not be available. This obviously jeopardizes the availability of the power plant and the reliability of the telecommunications system (or other systems) powered therefrom. Further, since a battery may only be charged and discharged a finite number of times, each cycle of complete discharge and charge necessarily reduces the overall life span of the battery.
Other methods, such as an ohmic technique or a partial discharge coupled with algorithmic calculations, may also be employed. Although these methods may be conveniently performed and may be relatively quick when compared to the full discharge method, these methods have not proven to be highly accurate.
Accordingly, what is needed in the art is a system and method for assessing the capacity of a battery that provides an accurate measurement of the battery's capacity in a short amount of time yet maintains the availability of the power plant at a satisfactory level.
SUMMARY OF THE INVENTION
To address the above-described deficiencies of the prior art, the present invention provides, a system for, and method of, assessing a capacity of a battery. In one embodiment, the system includes: (1) a voltage sensor, coupled to the battery, that develops a signal indicative of a parameter of a coup de fouet effect experienced by the battery as the battery is discharged and (2) a controller, coupled to the voltage sensor, that receives the signal and determines the capacity as a function thereof.
The present invention, in one aspect, introduces the concept of determining the capacity of a battery as a function of at least one of various parameters, which may arise from a phenomenon known as “coup de fouet.” As a fully charged battery is discharged, the voltage of the battery rapidly drops to a minimum voltage, herein is referred to as a “trough voltage.” The voltage then recovers to maximum voltage, herein referred to as a “peak voltage.” The voltage of the battery then gradually decreases from the peak voltage as the charge of the battery is dissipated. Depending on a rate at which the battery is being discharged and a temperature of the battery, the coup de fouet phenomenon may occur within one minute to within about 20 minutes. Since the trough voltage or the peak voltage may be sensed within a short time, usually a few minutes, after the discharge is initiated, the capacity of the battery may be determined without substantially discharging the battery.
Another aspect of the present invention provides a system for, and method of, assessing an age of a battery. In one embodiment, the system includes: (1) a voltage sensor, coupled to the battery, that develops a signal indicative of a parameter of a coup de fouet effect experienced by the battery as the battery is discharged and (2) a controller, coupled to the voltage sensor, that receives the signal and determines the age as a function thereof.
In one embodiment of the present invention, the parameter is a trough voltage of the battery. The controller may determine the capacity (or the age) of the battery as a function of the trough voltage. In an alternative embodiment, the parameter is a peak voltage of the battery. The controller may determine the capacity (or the age) of the battery as a function of the peak voltage. The controller may compare the trough voltage or the peak voltage of the battery under test to data obtained from discharging other similar batteries (but having varying capacities) to determine the capacity or the age of the battery under test.
The system advantageously discharges the battery until the trough voltage or the peak voltage is sensed. The battery need not be further discharged once the trough voltage or the peak voltage has been sensed, thereby reducing the amount of time required to discharge and recharge the battery.
In another embodiment of the present invention, the controller may receive a signal indicative of a battery voltage of the battery for a period of time while the battery is experiencing the coup de fouet effect and determine the capacity (or the age) of the battery as a function of a change or changes in the signal during the period of time. By periodically measuring the battery voltage during the period of time, the capacity (or the age) of the battery may be determined without necessitating discharge until the trough voltage or peak voltage is reached. The battery voltage of the battery under test may be plotted with respect to time and compared to data obtained from discharging other comparable batteries to determine the capacity (or the age) of the battery under test.
In one embodiment of the present invention, the system discharges the battery at a substantially constan
Toatley , Jr. Gregory J.
Tyco Electronics Logistics AG
Wong Peter S.
LandOfFree
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