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Browse Prior Art Database

Method of Detecting Battery Connection to Charger Circuits

IP.com Disclosure Number: IPCOM000118505D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 133K

Publishing Venue

IBM

Related People

Berglund, NC: AUTHOR [+3]

Abstract

Disclosed is a method of detecting when a +24V lead-acid battery string is disconnected from the output of a battery charger of a computer system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 45% of the total text.

Method of Detecting Battery Connection to Charger Circuits

      Disclosed is a method of detecting when a +24V lead-acid
battery string is disconnected from the output of a battery charger
of a computer system.

      The power system of some computers is based on a +29V DC
distributed power bus.  The battery back-up of these computer systems
powers the +29V bus in case of an AC mains failure.  While most
components internal to a computer system will last for ten years or
more, it is certain the internal lead-acid batteries will last an
average of four years.  When the batteries are worn out, they must be
disconnected from the computer and replaced with new batteries.  It
is desirable to replace the worn out batteries while the computer is
operating.  In other words, the batteries should be concurrently
maintainable.

      The Figure shows how the batteries are connected to the +29V
and ground busses of large computer systems.  The batteries are
physically located external to the charger circuit enclosure.  This
allows old, worn out batteries to be replaced in the field without
the cost of replacing still operational battery charger circuit
assemblies.  The positive terminal of the +24V battery string
connects to the +29V DC bus through the +29V BUS DISCHARGE SWITCHES
and the BATTERY ISOLATION DIODE.  The +29V BUS DISCHARGE SWITCHES
keep the batteries from energizing the +29V bus when the computer is
shut off.  The BATTERY ISOLATION DIODE allows discharged batteries to
be charged in a controlled manner when the +29V bus is up.  The
negative terminal of the +24V battery string connects to the system
ground bus through a SAFETY FUSE and SENSE RESISTORS.  If a system
fault occurs that draws an excessive amount of energy through the
charger circuits, the SAFETY FUSE will open before the charger
circuits combust.  The SENSE RESISTORS are used by the charger
circuits to detect when and how much current is being sourced by the
batteries.  The Figure also shows a BATTERY SENSOR circuit.  This
sensor is used by the charging circuits to sense the amplitude of the
battery voltage.

      In present computer systems, the battery charger is continually
charging the batteries.  When batteries are fully charged, the
charger operates in a float charging state.  When batteries are at
their end-of-life, they are still charged and will be used to back up
the system until new replacement batteries have been installed.  When
batteries have been determined to be at their end-of-life, the
computer operating system instructs computer service personnel to
replace the old batteries with new batteries.  Service personnel are
instructed to replace the old batteries without shutting off the
computer.  When batteries are disconnected from a charger while the
charger is running, the charger faults off with an overvoltage
indication.  This fault is due to the load being abruptly removed
from the charger power converter output.

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