Battery cutoff timer

Details Battery cutoff timer Battery cutoff timer

2000-10-19

2002-09-03

Toatley, Gregory (Department: 2838)

Electricity: battery or capacitor charging or discharging

Battery or cell discharging

With charging

C320S130000

Reexamination Certificate

active

06445163

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to electric power supplies for electronic equipment, and in particular to methods and systems for managing battery backup power for systems involving telecommunications and other data-processing equipment and networks.
Telecommunications and data processing equipment and networks typically use electrical power. The electrical power may be most commonly supplied, in the first instance, by the public electric power grid, i.e., by commercial power utilities. It may also be supplied by dedicated electrical generators.
Regardless of the source of electrical power, such sources cannot be considered fully reliable. Even the most well-maintained commercial power utilities, for instance, may experience from time to time cessations in service; for instance, because of extraordinarily high demand, or due to lightning strikes, transformer failures, circuit breaker trippings, and other phenomena that may affect electrical supply networks.
Power outages in the default electrical supply network may be of considerable detriment to a telecommunications or data processing network. Thus, various provisions are made by telecommunications and other network providers or infrastructure managers, or by customers, for ensuring that a backup power supply source is available. For instance, it would be highly undesirable for voice telephone service (referred to in the industry as “POTS”) to become unavailable each time the local electric power supply experienced a transient or lasting outage. Among other things, access to emergency police/medical/fire or “911” service could be disrupted or impaired. Such a result is unacceptable from a technical or public policy standpoint. As a rule of thumb, those who manage telecommunications systems and networks have the goal of ensuring that POTS or “lifeline” service will be available at least 99.999% of the time, and that backup power supplies will be available for POTS to ensure such service for a guaranteed period, typically eight (8) hours of continuous power outage.
It is known that most outages in public electric power networks will be of duration less than eight (8) hours. Further, it has been observed that most power outages fall into two broad categories; (a) transient outages caused by, e.g., circuit breaker trips (which can be cleared by automatic resetting of a breaker or re-routing of power, typically within a few minutes of the outage beginning); and (b) prolonged outages, i.e., those involving serious equipment failures or other problems that cannot be remediated automatically and that require a work crew to be dispatched to perform physical repairs on power lines, transformers, etc. at one or more remote sites. Such prolonged outages may be expected to last in the neighborhood of several hours.
Storage batteries (whether single batteries or a large group of batteries) provide perhaps the most effective form of backup power supply for telecommunication and data network equipment. Storage batteries may be maintained for backup by an individual corporate end user of the network, or by the network provider, or both, as desired. They are obviously also useful in the context of private networks, LANS, intranets, etc.
However, as storage batteries have a finite capacity or energy reserve, it is important to be able to measure the time for which effective power can be delivered by the backup storage batteries. In this connection, the aforementioned requirements for overall power reliability in the context of POTS are complicated by the fact that certain modem telecommunication or data networks may comprise a plurality of discrete services. For instance, a telecommunications network provider or servicer may provide both POTS and Digital Subscriber Line (DSL) data service to its end users, often over the same basic network. However, the POTS service and DSL data service may be transmitted in conjunction with separate servers or switches. These servers and switches may have differential power requirements. For instance, it is known that DSL requires greater electrical power than POTS (in part because a basic voice telephone signal is of comparatively small bandwidth compared to high-bandwidth, multiplexed data streams). Thus, maintaining backup power over an extended period for a DSL system will require far greater backup/battery capacity than providing backup power for POTS for the same duration.
Additionally, the “mission critical” nature of discrete telecommunications services may differ. As previously mentioned, there is a great emphasis on maintaining fully-reliable POTS service for all customers; while DSL service may of course be important to an end user, it is not generally deemed so mission critical, or so important to maintain as a lifeline service for all network users. Accordingly, given a choice, network providers will generally choose to dedicate the bulk of their efforts to reliable power backups toward guaranteeing maximal availability of one primary service (for instance POTS), while maintaining the best-possible, but lower-priority, power backup as to one or more secondary services. Essentially, the limited capacity of battery backup power requires prioritizing the competing demands for power from network service and equipment. For instance, most network administrators would accept a battery backup system that provided only enough battery backup power to power DSL service for typically one (1) hour or less of unavailability of outside power. This time period would provide a buffer zone that would maintain DSL service during the short-duration type of external power outage, though it could not guarantee full DSL service availability for a longer-duration power outage of perhaps several hours. Still, in a network comprising both POTS and DSL service, the ability to dedicate most of the backup power resources to providing uninterrupted POTS availability for up to eight (8) hours, while providing at least the selected or engineered (e.g., one (1) hour) backup period for DSL, would allow an orderly system shutdown of DSL/intranet or other data services, thus limiting damage to the network and end users and preserving communications and data integrity to a reasonable extent.
Prior art attempts at prioritizing power demand or managing backup power to optimize performance of a multi-component or multi-service data or telecommunications network, while protecting battery integrity, have not been fully satisfactory. In the past, low-voltage disconnect switches have been used to disconnect power loads from a backup battery (or group of batteries) when the voltage diminished below a certain point. While voltage deterioration provides a good rough estimate of decreasing battery charge and/or the threat of over-draining the battery, low-voltage disconnect switches have the disadvantage that they do not necessarily provide a fully predictable duration of backup power. Rather, the switch disconnects one or more loads automatically upon a prescribed voltage diminution.
In connection with such a system, and given the desirability of being able to predict with accuracy the particular amount of backup time to be devoted to each system or network resource or service, it would not be possible to guarantee any exact backup time for all services. Rather, at best, one could estimate the time at which battery output voltage would decrease to the switchoff threshold (say, 47 Volts, which corresponds with roughly eighty percent (80%) of beginning voltage) under estimated use conditions, and define this time as an estimated cutoff time. However, this is not a fully satisfactory approach because: (a) it does not provide a guaranteed backup time for the secondary device or service, but rather simply an estimated backup time, such that a premature cutoff could take place if the estimate were incorrect (causing such problems as, for instance, interruption of an orderly DSL shutdown initiated with the expectation that slightly or substantially more backup power would be available than actually occurred); and (b) the es

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