Browse Prior Art Database

ENHANCED BATTERY RECOGNITION SCHEMES

IP.com Disclosure Number: IPCOM000007784D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2002-Apr-23
Document File: 5 page(s) / 206K

Publishing Venue

Motorola

Related People

Joseph PatiƱo: AUTHOR [+3]

Abstract

Existing battery recognition schemes use one capacity resistor (Rc) to define the battery type/ capacity which is limited to thirteen possible values that can be resolved. As different battery chemis- tries and capacities continue to increase in number, the need for additional definable battery type/capaci- ties are needed. The inventions below provide a means of expanding this battery type recognition scheme. In approach one this is done by detecting two independent capacity resistors (Rcl and Rc2) without adding any additional contacts and still being able to read the thermistor (Rt) without any loss of resolution to the temperature sensing circuit. In approach two this is done by switching between two independent capacity resistor (Rc) ranges by using two independent pull up resistors in the charger.

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Page 1 of 5

M-LA Technical Developments

ENHANCED BATTERY RECOGNITION SCHEMES

by Joseph Patitio, Robert Stengel and Henry Bogut

teen different distinguishable battery type/capacities are capable with the existing scheme.

  Existing battery recognition schemes use one capacity resistor (Rc) to define the battery type/ capacity which is limited to thirteen possible values that can be resolved. As different battery chemis- tries and capacities continue to increase in number, the need for additional definable battery type/capaci- ties are needed. The inventions below provide a means of expanding this battery type recognition scheme. In approach one this is done by detecting two independent capacity resistors (Rcl and Rc2) without adding any additional contacts and still being able to read the thermistor (Rt) without any loss of resolution to the temperature sensing circuit. In approach two this is done by switching between two independent capacity resistor (Rc) ranges by using two independent pull up resistors in the charger.

  Refer to "Existing Block diagram" attached. Existing batteries use two battery connections to determine the battery's temperature (Rt) and bat- tery type/capacity (Rc). This is done by reading the resistor divider voltage presented to the corresponding A/D inputs. Typically the charger presents a 10K pull to both the Rt and Rc lines. Because of the tolerances to the pps AID, 5 volt regulator, pull up resistor and the battery's capacity resistor, only thir-

  Refer to "Proposed Block Diagram #l" attached. This invention uses the capability of the charger's pp to read an A/D voltage to calculate a correspond- ing resistance. By switching the pull up resistor on independently the values for Rt, Rcl and Rc2 can be determined.

(STATE 1) To determine the Rt value:

  Output 1 is pulled low and output 2 is pulled high. This causes transistor Ql to be turned off via resistor Rl and transistor Q2 to be turned on via resistor R3. When Ql is turned off, no voltage is switched onto the Rc line. When 42 is turned on, 5 volts is switched onto the Rt line via pull up resistor R4. In this contiguration, the diode D2 acts to switch resistors Rcl and Rc2 out of the circuit. Thus the voltage seen by A/D3 is resistor divider circuit of the known charger pull up resistor (R4) and battery thermistor (Rt). So the resistance of the Rt element can be determined as follows:

APPROACH #I:

.A/D2

vA/D3= V3=15)'

(Rt )+ (R4)

0 McMm,a, 1°C. 1996

101 August 1996

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8 M-LA Technical Developments

Rt = [V3) l (R4)

(5) - W3)

(STATE 2) To determine the Rcl and Rc2 values:

  Output 2 is pulled low and output 1 is pulled high. This causes transistor Ql to be turned on via resistor Rl and transistor Q2 to be turned off via resistor R3. When 42 is turned off, no voltage is switched onto the Rt line. When Ql is turned on, 5 volts is switched onto the Rc line via pull up resistor

R2. In this configuration, the c...