Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

High Power Discharge Capacity Test for Lead Acid Batteries

IP.com Disclosure Number: IPCOM000117157D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 6 page(s) / 251K

Publishing Venue

IBM

Related People

Berglund, NC: AUTHOR [+5]

Abstract

An algorithm to measure the energy capacity of lead-acid batteries internal to a computer system without risking system availability or completely discharging the internal batteries is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 24% of the total text.

High Power Discharge Capacity Test for Lead Acid Batteries

      An algorithm to measure the energy capacity of lead-acid
batteries internal to a computer system without risking system
availability or completely discharging the internal batteries is
disclosed.

      A computer contains lead-acid batteries to facilitate memory
dump during Alternate Current (AC) mains outages.  Computer users
depend on this battery back-up to work so the memory dump can be
implemented resulting in faster Initial Program Load (IPL) of the
computer when the AC utility returns.  If a battery back-up system
does not work and an AC outage occurs, users can be down for several
days instead of a few hours after AC mains returns.  To maximize
computer availability, it is very important to determine the status
of the back-up system before an AC mains outage occurs.

      The most important and perishable components of a battery
back-up system are the batteries.  On average, sealed lead-acid
batteries have a life span of four to five years.  However, each
individual battery set will fail at specific times depending on
temperature, frequency of usage, type of usage and other
uncontrollable field factors.  To minimize down-time, battery failure
date must be pinpointed.  Also, all batteries including lead-acid
pose environmental concerns.  It would be costly and irresponsible to
replace all lead-acid batteries after two or three years of use if
the batteries being replaced are still capable of backing up a
computer system.

      Since the reason for having a battery back-up system is to
minimize down-time, any method of testing the back-up system must not
put the system availability at risk.  An example of this would be
turning off the AC-to-DC power system when AC is good in order to
test the battery back-up system.  If the battery back-up fails during
this type of test, the computer system will crash.

      The duration of most AC mains failures is less than 30 seconds.
It is desirable at the conclusion of a battery capacity test that
there be enough energy in the back-up system to cover most AC outages
immediately following a test.

      To summarize: it is desirable to design a battery capacity
test method that accurately portrays the energy storage capability of
a particular system, does not endanger the availability, and does not
completely deplete the energy of the battery back-up system.

      The batteries to be tested are contained in a distributed power
system.  The power system is made up of current sharing AC-to-29VDC
power supplies connected to 29VDC-to-DC point-of-load regulators.
The batteries in the system are connected to the +29V bus.  When the
+29V bus fails due to AC mains failure or power supply fault, the
battery assemblies become the energy source for the +29V bus.
Integral to the power supplies and battery units is the System Power

Control Network (SPCN).  SPCN is a microprocessor-based diagnostic
and...