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BATTERY LOAD DETECTION CIRCUIT

IP.com Disclosure Number: IPCOM000007344D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-18
Document File: 2 page(s) / 96K

Publishing Venue

Motorola

Related People

Frank McCaleb: AUTHOR [+3]

Abstract

With increased energy requirements in portable radios and other battery powered equipment, users are confronted with the problem that attached bat- teries may actually discharge rather than charge while equipment is on and in the charger. An operational example of this dilemma is a two way radio that is turned on and put into the charger. The charger sup- plies a full C rate charge to the battery and it termi- nates properly at a full capacity. Following termina- tion, the battery is standard charged at a Cl10 to C/25 rate. Unfortunately, the radio standby current plus any receive or transmit activity easily exceeds the charge rate and discharges the battery even as it is in the charger pocket.

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MOTOROLA Technical Developments Volume 24 March 1995

BATTERY LOAD DETECTION CIRCUIT

by Frank McCaleb, Kuruvilla Valakuzhy, Scott Garrett

  With increased energy requirements in portable radios and other battery powered equipment, users are confronted with the problem that attached bat- teries may actually discharge rather than charge while equipment is on and in the charger. An operational example of this dilemma is a two way radio that is turned on and put into the charger. The charger sup- plies a full C rate charge to the battery and it termi- nates properly at a full capacity. Following termina- tion, the battery is standard charged at a Cl10 to C/25 rate. Unfortunately, the radio standby current plus any receive or transmit activity easily exceeds the charge rate and discharges the battery even as it is in the charger pocket.

  The obvious approach to address this problem is an increased charge rate. Unfortunately, simply increasing the charge rate will affect other parame- ters. If, in the case of the two way radio, we increase the charge rate and the radio is charged while turned off, the battery will be subjected to an abusive over- charge. An alternative would be to simply advise the user not to charge with the device turned on, however, this approach is less than a sure thing and may cause Customer confusion, concern and dissatisfaction.

  The problem continues today with a typical tnmking product. For a battery with a specified capac- ity of 1,200 mAH, the standard charge rate is set at 70 mA. The radio standby drain is 65 mA meaning that any receive or transmit activity will not only preclude top-off but will discharge in the charger. This problem is currently resulting in the loss of both customer satisfaction and sales.

  The invention described herein will allow the charger to determine if the battery load is active and for additional charging current as required. The

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