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BATTERY CAPACITY AND THERMISTOR IDENTIFICATION SCHEME WITH A TWO CONTACT BATTERY

IP.com Disclosure Number: IPCOM000007604D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-09

Publishing Venue

Motorola

Related People

Authors:
Joseph Patiiio

Abstract

This proposal eliminates two of the four battery contacts presently necessary on the battery to deter- mine the battery's capacity and battery's tempera- ture or thermistor value. The proposal uses the capa- bility of the charger's pp to read an A/D voltage to calculate a corresponding resistance. In the existing scheme, two independent A/Ds are used to deter- mine the capacity resistor (Rc) and the thermistor (Rt) value. Since the pull up resistor value is a known constant, the tip can calculate the resistance presented to the A/D for either Rc or Rt. The proposal elimi- nates the need for both of these lines, their corresponding contacts, and 1 of the 2 A/Ds. This is accomplished through the use of3 switches (Ql, 42, and Q3). Refer to block diagram attached. When determining the capacity of the battery, the charge current circuit will be disabled and the switches will be configured in the following manner.