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Pulse Charging Techniques of Nickel Cadmium Batteries

IP.com Disclosure Number: IPCOM000106695D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Pantelakis, T: AUTHOR [+2]

Abstract

Described is a hardware implementation that enables Ni-Cad batteries to be charged rapidly using pulse charging techniques so as to reduce charging time.

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This is the abbreviated version, containing approximately 73% of the total text.

Pulse Charging Techniques of Nickel Cadmium Batteries

      Described is a hardware implementation that enables Ni-Cad
batteries to be charged rapidly using pulse charging techniques so as
to reduce charging time.

      A high charging current is chosen so that the average current
supplied to the battery never exceeds its capacity rating.  If a
battery has a one ampere hour rating, it is charged at a rate of one
ampere for less than one hour.  As a result, in 25% duty cycle
applications, a four ampere or less current is supplied 25% of the
time for one hour.  When one battery is not being charged, another
battery can be receiving a pulse charge.  Fig. 1 shows the charge
timing relationship.

      By using this method, a reduction in the number of components
required can be achieved since only one circuit controls the charging
current and shutoff voltage needs.  The circuit is connected to each
battery pack during its ON period.  The technique offers the
advantage of making it easier to accurately measure the voltage at
which charging is complete and deciding when the charging process
should be stopped.  Fig. 2 shows the circuitry of a typical battery
when the VA voltage is measured.

      The apparent voltage VA measured across the cell while charging
depends on the value of Rs and the charge current supplied to the
battery.  For example, the voltage measured at the cell goes up when
the charging current goes up, or when the value of Rs for the ce...