Browse Prior Art Database

BATTERY WITH CODE RESISTOR NEEDING NO ADDITIONAL CONTACT

IP.com Disclosure Number: IPCOM000007051D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2002-Feb-21
Document File: 2 page(s) / 90K

Publishing Venue

Motorola

Related People

Scott M. Garrett: AUTHOR

Abstract

Code resistors are used in batteries to allow a charger to adjust the current output so that the same "c" rate can be applied to different capacity batter- ies (i.e. a 550 mAH battery is charged at 550 mA while a 1500 mAH battery is charged at 1.5 A). By doing this, different capacity batteries will be recharged in approximately the same time, and their useful service life is maximized. Presently, code resis- tors have their own dedicated electrical contact for both the battery and the charger. These contacts not only represent an increase in cost but also an addi- tional opportunity for product failure in both bat- tery and charger. Furthermore, the only time the code resistor is used on most batteries is at the begin- ning of the charge process, before current is applied to the battery. Which means that 99% of the time, the code resistor does nothing. Therefore it would be advantageous to eliminate the code resistor con- tact while retaining the ability to determine the cor- rect charger current when a battery is inserted into a charger. This brief article describes a method to accomplish both.

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MOIOROLA INC. Technical Developments Volume20 October 1993

BATTERY WITH CODE RESISTOR NEEDING NO ADDITIONAL CONTACT

by Scott M. Garrett

  Code resistors are used in batteries to allow a charger to adjust the current output so that the same "c" rate can be applied to different capacity batter- ies (i.e. a 550 mAH battery is charged at 550 mA while a 1500 mAH battery is charged at 1.5 A). By doing this, different capacity batteries will be recharged in approximately the same time, and their useful service life is maximized. Presently, code resis- tors have their own dedicated electrical contact for both the battery and the charger. These contacts not only represent an increase in cost but also an addi- tional opportunity for product failure in both bat- tery and charger. Furthermore, the only time the code resistor is used on most batteries is at the begin- ning of the charge process, before current is applied to the battery. Which means that 99% of the time, the code resistor does nothing. Therefore it would be advantageous to eliminate the code resistor con- tact while retaining the ability to determine the cor- rect charger current when a battery is inserted into a charger. This brief article describes a method to accomplish both.

  Figure la shows the present charger/battery sys- tem with all unrelated circuits absent for clarity, There is a control circuit that, among other things, con- trols the electrical current supplied to the battery,

There is a means to enable the current, represented by S,, which may be an electronic switch, such as a MOSFET, relay, or any other means by which cur- rent flow is controlled and/or interrupted. Resistor

Rd represeents a circuit which is completed by the ba...