Browse Prior Art Database

Microprocessor Controlled Battery Charger

IP.com Disclosure Number: IPCOM000113824D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 235K

Publishing Venue

IBM

Related People

Pantelakis, T: AUTHOR

Abstract

Described is a hardware implementation of a microprocessor controlled battery charger that provides the capability of controlling the recharging and rejuvenating of batteries using pulse charging techniques.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 26% of the total text.

Microprocessor Controlled Battery Charger

      Described is a hardware implementation of a microprocessor
controlled battery charger that provides the capability of
controlling the recharging and rejuvenating of batteries using pulse
charging techniques.

      In prior art, battery chargers for Ni-cad or NiMH type
batteries had the capability of just charging the battery packs and
could not diagnose defective or worn out battery packs, nor could
they rejuvenate packs which had reduced capacity due to frequent
recharging after shallow discharges.  This induced "memory" effect
greatly reduced the life of the battery pack if it was not erased by
completely discharging and then fully recharging the pack.

      The concept described herein provides the capability to enable
the charger to: recharge batteries, including battery charging;
rejuvenating; and to provide advanced diagnostics utilizing pulse
charging techniques.  A microprocessor is used to control the rapid
charging, deep cycling and to diagnose defective battery packs for up
to three packs concurrently.  The features of the microprocessor
controlled battery charger include the following:
  o  The ability to the measure battery pack voltage during a
"float" or no charge period in the charging process.  This is an
improvement over prior art designs that attempt to measure the
voltage while charging and then either discontinuing charging or
reducing the charge rate when a fixed voltage is reached.  The
magnitude of that voltage will vary depending upon the impedance
of the battery, which can vary with age.  By measuring the
battery voltage during a float period, the measurement is
independent of cell impedance.  In addition, by measuring the
battery voltage during the float period, no ripple or noise from
the charging source is introduced into the measurement.  In prior
art, various techniques were used to measure the battery voltage
while charging in an effert to filter out the noise from the
readings.
  o  An analog current loop is programmed by a Digital/Analog (D/A)
controller from the microprocessor to allow accurate and stable
real-time control of the charge current.  This provides a simple
and precise control which relies on the microprocessor to adjust
the charger output voltage based on current measurements in an
attempt to provide a constant current output.  In the prior art,
a "set, compare, and loop" method would introduce errors into the
voltage measurements because the battery terminal voltage could
change during the voltage sampling period due to changes in the
current flowing into the battery.  Also, the battery current
could change between update cycles since the microprocessor was
updating the output voltage as the battery terminal voltage
increases, because the charging current flowing decreases during
that time.  This created an added error signal in the battery
terminal voltage measured while charging due to the varying
currents through...